Mineral(krauset.al 1959)

Mineral adalah suatu zat yang terdapat dalam alam dengan komposisi kimia yang khas dan biasanya mempunyai

struktur kristal yang jelas, yang kadang-kadang dapat menjelma dalam bentuk geometris tertentu.Istilah mineral dapat mempunyai bermacam-macam makna; sukar untuk mendefinisikan mineral dan oleh karena

itu kebanyakan orang mengatakan, bahwa mineral ialah satu frase yang terdapat dalam alam. Sebagaimana kita ketahui ada mineral yang berbentuk :

• Lempeng• Tiang

• Limas• Kubus

Batu permata kalau ditelaah adalah merupakan campuran dari unsur-unsur mineral.Setiap mineral yang dapat membesar tanpa gangguan akan memperkembangkan bentuk kristalnya yang khas,

yaitu suatu wajah lahiriah yang dihasilkan struktur kristalen (bentuk kristal). Ada mineral dalam keadaan Amorf, yang artinya tak mempunyai bangunan dan susunan kristal sendiri (mis kaca & opal). Tiap-tiap pengkristalan akan

makin bagus hasilnya jika berlangsungnya proses itu makin tenang dan lambat.

Kristal

Kristal adalah sebuah benda yang homogen, berbentuk sangat geometris dan atom-atomnya tersusun dalam

sebuah kisi-kisi kristal,karena bangunan kisi-kisi kristal tersebut berbeda-beda maka sifatnya juga berlainan. Kristal dapat terbentuk dalam alam (mineral) atau di laboratorium. Kristal artinya mempunyai bentuk yang agak setangkup

(symetris) dan yang pada banyak sisinya terbatas oleh bidang datar, sehingga memberi bangin yang tersendiri sifatnya kepada mineral yang bersangkutan.

Benda padat yang terdiri dari atom-atom yang tersusun rapi dikatakan mempunyai struktur kristalen. Dalam suasana yang baik benda kristalen dapat mempunyai batas bidang rata-rata & benda itu dinamakan kristal

(HABLUR) & bidang rata itu disebut muka krsital.

Ada 32 macam gelas kristal yang dipersatukan dalam 6 sistem kristal, yaitu:

1. REGULER, Kubus atau ISOMETRIK ketiga poros sama panjang dan berpotongan tegak lurus satu sama lain (contoh : intan, pirit, garam batu)

2. TETRAGONAL (berbintang empat) ketiga poros tegak lurus satu sama lain, dua poros sama panjang sedangkan poros ketiga berbeda (contoh chalkopirit, rutil, zircon).

3. HEKSAGONAL (berbintang enam) Hablur ini mempunyai empat poros, tiga poros sama panjang dan terletak dalam satu bidang, bersilangdengan sudut 120 derajat (60 derajat), tetapi poros ke-empat tegak

lurus atas bidang itu dan panjangnya berbeda (contoh apalit, beryl, korundum).4. ORTOROMBIS (irisan wajik) ketiga poros tidak sama panjang du poros berpotongan siku-siku dan poros

ketiga memotong miring bidang kedua poros tadi (berit, belerang, topaz)5. MONOKLIN (miring sebelah) ketiga poros tidak sama panjang, dua dari porosnya berpotongan sorong &

poros ketiga tegak lurus atas kedua poros tadi (gips, muskovit, augit)6. TRIKLIN (miring, ketiga arah) ketiga poros tidak sama panjang dan berpotongan serong satu sama

lain(albit, anortit, distin)Bentuk kristal dibagi dalam 6 tata hablur yang didasarkan:

• perbandingan panjang poros – poros hablur• besarnya sudut persilangan poros – poros hablur

Gores

kristal / mineral yang mempunyai kekerasan < 7 jika digosokkan pada lempengan porselin yang kasar biasanya

meninggalkan ditempat penggosokan tsb suatu garis yang karakteristik dan seringkali berwarna lain dari mineral itu sendiri.

• Pirit yang warnanya kuning emas meninggalkan garis hitam.• Hematit (Fe2O3) yang berkilap kelogam – logaman atau memberigaris merah darah

• Fluisvat memberikan garis putih (mineral yang berwarna terang tetapi memberi garis putih)

Skala Kekerasan MOH's

Kekerasan adalah sebuah sifat fisik lain, yang dipengaruhi oleh tata letak intern dari atom. Untuk mengukur kekerasan mineral dipakai Skala Kekerasan MOHS (1773-1839).

1. Talk, mudah digores dengan kuku ibu jari2. GIPS, mudah digores dengan kuku ibu jari

3. Kalsit, mudah digores dengan pisau4. Fluorit, mudah digores dengan pisau

5. Apatit, dapat dipotong dengan pisau (agak sukar)6. Ortoklas, dapat dicuwil tipis-tipis dengan pisau dibagian pinggir

7. Kwarsa, dapat menggores kaca8. Topaz, dapat menggores kaca

9. Korundum, dapat mengores topaz10.Intan, dapat menggores korundum

Bentuk Kristal Intan ialah benda padat besisi delapan (OKTAHEDRON)

1. K = 1 : Talk/Silikat magnesia yang mengandung air2. K = 2 : Gips (CaSO4), batu tahu

3. K = 3 : Kalsit (CaCo3)

4. K = 4 : Vluispat (CaF2)

5. K = 5 : Apatit mengandung chloor

6. K = 6 : Veldspat, kaca tingkap7. K = 7 : Kwarsa, pisau dari baja

8. K = 8 : Topas; Silikat alumunium yang mengandung borium, batu permata9. K = 9 : Korsum (Al2O3 dalam corak merah, batu permata delima, corak biru batu nilam/safir)

10.K = 10 : intan batu permataMasing-masing mineral tersebut diatas dapat menggores mineral lain yang bernomor lebih kecil dan dapat digores

oleh mineral lain yang bernonor lebih besar. Dengan lain perkataan SKALA MOHS adalah Skala relative. Dari segi kekerasan mutlak skala ini masih dapat dipakai sampai yang ke 9, artinya no. 9 kira-kira 9 kali sekeras no. 1, tetapi

bagi no. 10 adalah 42 kali sekeras no. 1

K.E. Kinge (1860) dalam Han Sam Kay mengelompokkan batu permata yang dijadikan perhiasan dalam lima belas

kelas sebagai berikut :

1. Batu permata Kelas I, Nilai Keras antara 8 s/d 10

2. Batu Permata kelas II, Nilai Keras antara 7 s/d 83. Batu permata Kelas III

Batu permata kelas ini tergolong jenis batu mulia dan batu mulia tanggung, nilai kerasnya kira-kira 7, sebagian besar terdiri dari asam kersik (kiezelzuur), keculai pirus (tuquois)

4. Batu-Batu mulia Tanggung yaitu batu kelas IV, nilai keras antara 4 – 7

5. Batu kelas V

Batu kelas V nilai kerasnya dan kadar berat jenisnya sangat berbeda-beda. Warnanya gelap (kusam) dan kebanyakan agak keruh, tidak tembus cahaya, batunya sedikit mengkilap, dan harganyapun amat murah

bila dibandingkan dengan harga batu mulia.Dalam kelas ini termasuk batu marmer dan batu kelas V tidak tergolong batu mulia.

Belahan

Belah adalah kecenderungan batu permata untuk membelah kearah tertentu menyusur permukaan bidang rata, lebih spesifik lagi ia menunjukkan kearah mana ikatan-ikatan diantara atom relative lemah dan biasanya reta-retak

menunjukan arah belah.Belahan ialah sifat untuk menjadi belah menurut bidang yang agak sama licinnya

• belahan baik sekali• baik

• sedang• buruk

• tidak ada belahan sama sekali

Warna

Kenapa kita dapat melihat berbagai warna ?

Warna dapat dilihat ketika terjadi beberapa proses pemindahan panjang gelombang, beberapa menyerap panjang gelombang spesifik dari spektrum yang dapat dilihat. Spektrum yang dapat dilihat terdiri dari warna merah, oranye,

kuning, hijau, biru, nila dan violet.

Ketika terjadi pemindahan panjang gelombang akan mempengaruhi energi dan akan terjadi perubahan warna dan

jika permata itu mengandung besi biasanya akan terlihat berwarna kelam, sedangkan yang mengandung alumunium biasanya terlihat berwarna cerah, tetapi juga ada mineral yang berwarna tetap seperti air (berkristal)

dan dinamakan Idhiochromatic

Disini warna merupakan sifat pembawaan disebabkan karena ada sesuatu zat dalam permata sebagai biang warna

(pigment agent) yang merupakan mineral-mineral yaitu : belerang warnanya kuning; malakit warnanya hijau; azurite warnanya biru; pirit warnanya kuning; magatit warnanya hitam; augit warnanya hijau; gutit warnanya kuning

hingga coklat; hematite warnanya merah dsbnya.

Ada juga mineral yang mempunyai warna bermacam-macam dan diistilahkan allokhromatik, hal ini disebabkan

kehadiran zat warna (pigmen), terkurungnya sesuatu benda (inclusion) atau kehadiran zat campuran (Impurities). Impurities adalah unsur-unsur yang antara lain terdiri dari Ti, V, Cr, Mn, Fe, Co, Ni, Cu, dan biasanya tidak hadir

dalam campuran murni, unsur-unsur yang terkonsentrasi dalam batu permata rendah.

Aneka warna batu permata ini sangat mempersona manusia sehingga manusia memberi gelar “mulia pada batu-”batu itu, contoh intan yang hanya terdiri dari satu unsur mineral yakni zat arang merupakan benda yang padat yang bersisi delapan karena adanya zat campuran yang berbeda akan menyebabkan warna yang berbeda : tidak

berwarna, kuning, kuning muda, agak kebiru-biruan, merah, biru agak hijau, merah jambu, merah muda, agak kuning coklat, hitam yang dinamakan carbonado, hijau daun. Banyak mineral hanya memperlihatkam warna yang

terang pada bagian-bagian yang tipis sekali. Mineral yang lebih besar dan tebal selalu memberi kesan yang hitam, tanda demikian antara lain diperlihatkan oleh banyak mineral.

Warna hijau muda; jika warna tersebut makin tua berarti makin bertambah Kadar Fe didalam molekulnya.

Berat Jenis (BD)

Untuk mengetahui mineral yang belum diketahui Bdnya dipakai alat yang disebut cairan berat :

• Pertama : Bromoform (ChBr)

• Kedua : Joodmethylin (Ch2 J2)• Ketiga : Cclerici yaitu larutan Thallium malonat formiat

Mineral dengan BD < 2,68 mineral ringan

• kwarsa: 2,57

• albit: 2,62• oligoklas: 2,64

Mineral dengan BD > 2,68 mineral berat

• Labradorit: 2,70

• Anortit: 2,76• Augit hornblende: 3,20

• Maskotit: 2,90• Biotitit: 3,00

• Korundum: 3,20• Turmalin

Mineral dengan BD 3,3 – 4 mineral amat berat

• olifin

• starolit• granat / garnet

Mineral dengan BD > 4 dan kekerasan = 7

• Zirkon

BD = 2,65 Mineral tergolong dalam fraksi enteng dan bias rangkapnya tergolong rendah yaitu terdiri dari Kuarsa kristalen; bergkristal (tidak berwarna); amathis atau kecubung opal = sebetulnya gel asam kersik chalsedon;

jenis kristalnya jenis kripto (kwarsa kripto kristalen); k = 7; struktur kristalnya baru tampak jika dilihat dengan menggunakan mikroskop. agat; jenis kristalnya jenis kripto (kwarsa kripto kristalen) = k = 7; struktur kristalnya

baru tampak jika dilihat dengan menggunakan mikroskop Oniks, jenis kristalnya jenis kripto (kwarsa kripto kristalen) = k = 7; struktur kristalnya baru tampak jika dilihat dengan menggunakan mikroskop jaspis besi

kersik opal tanggung (half opal) = sifat membelah tidak ada pecahannya berupa kerang.

BD = 2,9 – 3,3 Nefrit = Jade = Giok {Ca2 (Mg, Fe)5 (OH)2Si8O22} aktinolit atau Amfibol kalsium magnesium

besi; bentuk menyerabut atau asbes tiform; warna kelabu, kehijau-hijauan atau kekuning-kuningan; adanya garis kembar; warna plagioklas putih, kadang – kadang kehijau-hijauan, hijau tua, coklat, hitam, kadang-kadang tembus

pandang (transparan), tembus cahaya (Translucent) atau opal; bidang belah berpotongan dengan sudut 550 dan 1250 ; K = 5 – 6; apabila dipanaskan mengeluarkan air yang menunjukkan bahwa ia terbentuk dalam suasana

hidro (perhatikan adanya gugusan OH) atau dikenal sebagai AMFIBOL.

BD = 3,3 – 3,6 Epidot ( H2 M4 “M6 Si6O26, M ); dari batu-batuan endapan atau sedimen yang lebih tua; k =” ’ ”

6,5; Hijau- hijau kekuning-kuningan, terdapat jenis yang berwarna merah; belahan baik; mengristal monoklin, prisma; bias cahaya dan bias rangkap kuat.

BD = 3,5 – 5,3 Granat/Garnet (M3 M2 SiO3O12); dari batuan sedimen tua; kristal reguler; bias cahaya keras,” ” ’ tidak berbias rangkap (Isotrop); K = 7; belahan baik; warna merah, merah coklat, kuning dan hijau jarang, tidak

berwarna sama sekali.

BD = 4 Korundum (Al2O3) tersusun sangat padat; tak berwarna –bermacam-macam warna; K = 9;

Oktahedron/Hexagonal; Bias tinggi; Bias rangkapnya rendah. (3,9 – 4,1) Spinel (M = Mg, Zr, Fe; M = Cr, Al,” ” ’ Mn); hijau tua; K = 7,5 – 8; Biasnya tinggi, Mengkristal secara reguler; bersifat isotrop dalam optiknya; belahannya

seringkali buruk

BD = 4,2 Ortit termasuk golongan Epidot hanya dalam persenyawaannya berbeda disebabkan kadar Ce yang

tinggi; K= 5,6; merah coklat, coklat merah tua – kuning atau coklat kuning; kristal gemuk seperti prisma; Turmalin {H9Al3(B.OH)2Si4O19}; K= 7; Heksagonal, belahan buruk, Bias sedang; Pleokroisnya sangat kuat; jernis seperti

air, Coklat biru sampai hitam, turmalin biru agak jarang diketemukan.

Tiap-tiap batu permata yang sudah dikenal berat jenisnya dapat diketahui nilai keras batu, dari berat batu dapatlah

dihitung kari dari permata tersebut. Karat adalah satuan berat yang setimbang dengan seperlima gram. Satuan ini disebut karat metric. Jika kita timbang berat intan, tidak dikatakan berat intan 1 gram tetapi berat intan adalah 5

karat, demikian yang lain batu rubi beratnya 17,8 karat, batu sapphire 7 karat dsbnya.

C

h

C

CH

CCromite Category Oxide mineral (Chromite )Chemical formula (Fe, Mg)Cr2O4

Identification

Color Black to brownish black; brown to brownish black on thin edges in transmitted light

Crystal habit Octahedral rare; massive to granularCrystal system Isometric; hexoctahedral H-M Symbol (4/m3 2/m) Space Group: F d3mCleavage None, parting may develop along {111}Fracture ConchoidalMohs scalehardness 5.5Luster SubmetallicStreak Dark brownDiaphaneity Translucent to opaque.Specific gravity 4.5 - 4.8Optical properties IsotropicRefractive index n == 2.08-2.16Other characteristics Weakly magneticChromite is found in peridotite from the Earth's mantle. It also occurs in layered ultramafic intrusive rocks.[7] In addition, it is found in metamorphic rocks such as some serpentinites. Ore deposits of chromite form as early

magmatic differentiates. It is commonly associated with olivine, magnetite, serpentine, and corundum. The vast Bushveld igneous complex of South Africa is a large layered mafic to ultramaficigneous body with some layers

consisting of 90% chromite making the rare rock type, chromitite.[8] The Stillwater igneous complex inMontana also contains significant chromite. Barbertonite is a hexagonal polymorph of stichtite, and along with stichtite, is an alteration product of chromite in serpentinite. Barbertonite has a close association with stichtite, chromite, and antigorite (Taylor et al.,

1973). Closely intermixed with its polymorph, analysis of absolute material is therefore non-existent. This has long been a topic of confusion. The main factors contributing to this are lack of sufficient crystallographic data and the

complex composition of the several species coupled with the inadequate nature of the chemical analysis available (Frondel et al. 1941). A further hurtle has been the lack of correlation of the publications on the subject. Barbertonite [Mg6Cr2(OH)16CO3.4H2O] a member of the hexagonal Sjogrenite group along with manasseite

[Mg6Al2(OH)16CO3.4H2O] and sjogrenite [Mg6Fe2(OH)16CO3.4H2O] (Palache et al., 2003). The rhombohedral Hydrotalcite group consists of the minerals: stichtite [3(Mg6Cr2(OH)16CO3.4H2O)], hydrotalcite

[3(Mg6Al2(OH)16CO3.4H2O)], and pyroaurite [3(Mg6Fe2(OH)16CO3.4H2O)]. These two isostructural groups are polymorphous in relation to each other (Palache et al., 1944). The structure of barbertonite has brucite-like layers alternating with inter layers. Neighboring brucite layers are stacked so that the hydroxyl groups are directly above one another (Taylor et al., 1973). In between brucite layers

are inter layers containing CO ions and H2O molecules (Taylor et al., 1973). Oxygen atoms are accommodated in a single set of sites distributed close to the axes that pass through the hydroxyl ions of adjacent brucite layers (Taylor et al., 1973). Found closely associated with stichtite, chromite, and antigote, barbertonite was first found in the Barberton district

in Transvaal, South Africa. It can also be found in the Ag-Pb mine in Dumas, Tasmania, Australia (Anthony et al., 2003). Read and Dixon (et al. 1933) stated that the mineral that was found in Cunningsburgh, Shetland Islands was

stichtite but it is now thought to be barbertonite because of the very similar indices of the minerals (Frondel et al. 1941). Barbertonite frequently occurs admixed with its rhombohedral analogue and as an alteration product of chromite in serpentinite (Anthony et al. 2003). Barbertonite was first found in the Barberton district in the South African providence of Mpumalanga, known as “the

land of the rising sun to its Siswati and Zulu speaking inhabitants. Barberton was originated in the 1880s gold rush” in the region, located in the De Kaap Valley and bordered by the Mkhonjwa Mountains. First flourishing, Barberton then diminished when its inhabitants moved away to the newly discovered gold fields on the reef.

Bentorite is a mineral with the chemical formula Ca6(Cr,Al)2(SO4)3(OH)12·26(H2O). It is colored violet to light violet. Its crystals are hexagonal to dihexagonal dipyramidal. It is transparent and has vitreous luster. It has

perfect cleavage. It is not radioactive. Bentorite is rated 2 on the Mohs Scale. The mineral was determined by Shulamit Gross in Hatrurim Formation of Danian age along the western margin of the Dead Sea, Israel, and named

for Y.K. Bentor, Professor at the Hebrew University, Jerusalem and the University of California, San Diego, California, USA, for his contributions to geology and mineralogy in Israel.

Chrome chalcedony is an green variety of the mineral chalcedony, colored by small quantities of chromium.[4] It is most commonly found in Zimbabwe, where it is known as Mtorolite,[5] Mtorodite,[6] or Matorolite.[7] Chrome chalcedony is similar in appearance to the better known chrysoprase, but differs in that whilst chrome

chalcedony is colored by chromium (as chromium(III) oxide), chrysoprase is colored by nickel.[4] The two can be distinguished with a Chelsea color filter, as chrome chalcedony will appear red, whilst chrysoprase will appear green.[4] [8] Chrome chalcedony (unlike chrysoprase) may also contain tiny black specks of chromite.[3]

Chrome chalcedony is (together with agate, carnelian, chrysoprase, heliotrope, onyx and others) a variety

of chalcedony. This is acryptocrystalline form of silica, consisting of fine intergrowths of the minerals quartz and moganite.[1]

Chrome chalcedony (known as mtorolite, mtorodite or matorolite) occurs in Zimbabwe, principally near to the mining town ofMtoroshanga, located on the Great Dyke geological feature.[5] It has also been discovered in western Australia, the Balkans, Bolivia,Turkey and the Ural mountains.[9] Chrome chalcedony was widely used in jewellery and seals throughout the Roman Empire. The source of the

mineral is unclear, as whilstPliny the Elder described it as coming from India, no deposits have been found there. It may have come from Anatolia (in modern dayTurkey) where deposits are known to exist.[9]

Chrome chalcedony disappeared from use sometime in the second century AD. It was only rediscovered when the

Zimbabwean deposits were found in the 1950s.[10]

Kalininite (Zn Cr 2S4) is a mineral found in Russia.

Knorringite is a mineral species belonging to the garnet group and forms a series with the species pyrope. It was

discovered in 1968 and is named after Oleg Von Knorring, a professor of mineralogy at the University of Leeds in England. Knorringite's chemical formula is Mg3Cr2(SiO4)3. Knorringite is a green, blue color with a Mohs

scale of mineral hardness of six to seven. Knorringite is a tracer mineral in the search for diamonds in kimberlite pipes.

Mariposite is a mineral which is a chromium-rich variety of mica, which imparts an attractive green color to the generally white dolomitic marble in which it is commonly found. It was named for Mariposa, California, though it

can be found in several places in the Sierra Nevadamountains. It is also found in a few locations

in Newfoundland, Canada, where it is called virginite, and Europe.

It is not an officially classified mineral, but is a chromium-rich phengite, which is a high silica variety of muscovite.

The chemical formula is K(Al,Cr)2(Al,Si)4O10(OH)2. It is the chromium that gives it its distinctive green color.

The term "mariposite" also refers to the stone in which the green mica is found. This stone is marble, containing

varying amounts of dolomiteand quartz. Larger proportions of quartz give it a more attractive, translucent appearance. It is used as a decorative construction material, in walls, monuments, and bridges. It is also made

into jewelry. This jewelry is sometimes sold under the trade name "Emerald Quartz".

(Figure :Mariposite)

Stichtite is a mineral, a carbonate of chromium and magnesium; formula Mg6Cr2C O 3(OH)16·4H2O. Its colour

ranges from pink through lilac to a rich purple colour. It is formed as an alteration product

from chromium containing serpentine.

Discovered in 1910 in Western Tasmania, Australia, it was first recognised by A.S. Wesley a former chief chemist

with the Mount Lyell Mining and Railway Company, it was named after Robert Carl Sticht the manager of the mine [1]

It was observed near the Adelaide Mine, Dundas - east of Zeehan, as well as on the southern shore of Macquarie

Harbour. It is exhibited in theWest Coast Pioneers Museum in Zeehan.

(Figure :Stichtite on Serpentinite)

Uvarovite is a chromium bearing garnet group species with the formula: Ca3Cr2(Si O 4)3. It was discovered in 1832

by Germain Henri Hesswho named it after Count Sergei Semenovitch Uvarov (1765-1855), a Russian statesman and amateur mineral collector.

Uvarovite is one of the rarer of the garnet group minerals, and is the only consistently green garnet species, with a beautiful emerald-green color. It occurs as well-formed fine sized crystals. Specimens of uvarovite are much sought

after by collectors for outstanding brilliance and color.

It is found associated with chromium ores in Spain, Russia, and Quebec in Canada. It also occurs

in Finland, Norway, and South Africa

Zhanghengite is a mineral consisting of 80% copper and zinc, 10% iron with the balance made up of chromium and aluminium. Its color is golden yellow. It was discovered in 1986 during the analysis of the Bo Xian

Meteorite and is named after Zhang Heng, an ancient Chinese astronomer. As well as being an astronomer, Zhang Heng was also a geologist who invented the first seismograph. Although recognized as a valid mineral it apparently

does not arise naturally on earth.

Zincochromite is a mineral; formula Zn Cr 2O4, It is the zinc analogue of Chromite, hence the name. Discovered in

1987 in South Karelia, Russia.

Physical Properties of Zoncochromite.

Color: Brownish Black.

Diaphaniety: Translucent to Opaque.

Habit: Euhedral Crystals - Occurs as well-formed crystals showing good external form.

Hardness: 5.8.

Luster: Sub Metallic.

Calculated Properties of Zincochromite.

Electron Density: Relectron=5.02 gm/cc.

Note: Zincochromite =5.32 gm/cc.] Fermion Index = 0.05395.

Boson Index = 0.94605.

Photoelectric: PEZincochromite = 24.45 barns/electron.

U=PEZincochromite x relectron= 122.61 barns/cc.

Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units).

Zincochromite is Not Radioactive

Bauxite

Bauxite is the most important aluminium ore. This form of rock consists mostly of

the minerals gibbsite Al(OH)3, boehmite -AlO(OH), andγ diaspore -AlO(OH), in aα mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anataseTiO2. Bauxite was named

after the village Les Baux in southern France, where it was first recognized as containing aluminium and named by

the French geologist Pierre Berthier in 1821.

Lateritic bauxites (silicate bauxites) are distinguished from karst bauxites (carbonate bauxites). The early

discovered carbonate bauxites occur predominantly in Europe and Jamaica above carbonate rocks (limestone and dolomite), where they were formed by lateritic weathering and residual accumulation of

intercalated clays or by clay dissolution residues of the limestone.

The lateritic bauxites are found mostly in the countries of the tropics.They were formed by lateritization (see laterite)

of various silicate rockssuch as granite, gneiss, basalt, syenite, and shale. In comparison with the iron-rich laterites, the formation of bauxites demands even more intense weathering conditions in a location with very good drainage.

This enables the dissolution of the kaolinite and the precipitation of the gibbsite. Zones with highest aluminium content are frequently located below a ferruginous surface layer. The aluminium hydroxide in the lateritic bauxite

deposits is almost exclusively gibbsite.

In 2007, Australia was one of the top producers of bauxite with almost one-third of the world's production, followed

by China, Brazil, Guinea, and India. Although aluminium demand is rapidly increasing, known reserves of its bauxite ore are sufficient to meet the worldwide demands for aluminium for many centuries, Increased aluminium

recycling, which has the advantage of lowering the cost in electric power in producing aluminium, will considerably extend the world's bauxite reserves.

Galena

Category Sulfide mineralChemical formula lead sulfide (PbS)Strunz classification II/C.15-40Dana classification 2.8.1.1Crystal symmetry 2/m 3 2/m

IdentificationColor Dark, lead gray and silveryCrystal habit Cubes and octahedra, tabular and sometimes skeletal crystalsCrystal system Isometric cF8, SpaceGroup Fm-3m, No. 225Twinning Contact and penetrationCleavage CubicFracture SubconchoidalMohs scalehardness 2.5 - 2.75Luster MetallicStreak Lead grayDiaphaneity OpaqueSpecific gravity 7.2 - 7.6Fusibility 2

Galena deposits often contain significant amounts of silver as included silver sulfide mineral phases or as limited

solid solution within the galena structure. These argentiferous galenas have long been the most important ore of silver in mining. In addition zinc, cadmium, antimony, arsenic and bismuth also occur in variable amounts in lead

ores. Selenium substitutes for sulfur in the structure constituting a solid solution series. The lead telluride mineral altaite has the same crystal structure as galena. Within the weathering or oxidation zone

galena alters toanglesite (lead sulfate) or cerussite (lead carbonate). Galena exposed to acid mine drainage can be oxidized to anglesite by naturally occurring bacteria and archaea, in a process similar to bioleaching [3]

Galena deposits are found in Wales, Germany, France, Romania, Austria, Belgium, Italy,Spain, Scotland, Ireland, England, Australia, Mexico,

and the United States. Noted deposits include those at Freiberg, Saxony; Cornwall,The Mendips, Somerset, Derbyshire, andCumberland, England; the Sullivan Mine of British

Columbia; and Broken Hill, Australia. Galena also occurs at Mount Hermon in NorthernIsrael. In the United States, it occurs most notably in the Mississippi Valley type deposits of the Lead Belt in southeastern Missouri, and in

the Driftless Area of Illinois, Iowa and Wisconsin. The economic importance of galena to the early history of the Driftless Area was so great that one of the towns in the region was named Galena, Illinois.

Galena also was a major mineral of the zinc-lead mines of the tri-state district around Joplin in southwestern Missouri and the adjoining areas of Kansas and Oklahoma. Galena is also an important ore mineral in the silver

mining regions of Colorado, Idaho, Utah and Montana. Of the latter, the Coeur d'Alene district of northern Idaho

was most prominent. Galena is the official state mineral of the U.S. states of Missouri and Wisconsin.

One of the earliest uses of galena was as kohl, which in Ancient Egypt, was applied around the eyes to reduce the

glare of the desert sun and to repel flies, which were a potential source of disease.[5]

Galena is a semiconductor with a small bandgap of about 0.4 eV which found use in earlywireless communication

systems. For example, it was used as the crystal in crystal radio sets, in which it was used as a point-contact diode to detect the radio signals. The galena crystal was used with a safety pin or similar sharp wire, which

was known as a "cat's whisker". Making such wireless sets was a popular home hobby in Britain and other European countries during the 1930s. Derbyshire was one of the main areas where galena was mined.

Scientists that were linked to this application are Karl Ferdinand Braun and Sir Jagdish Bose. In modern wireless communication systems, galena detectors have been replaced by more reliable semiconductor devices,

though silicon point-contact microwave detectors still exist in the market.

Manganese

Manganite is a mineral. Its composition is manganese oxide-hydroxide, MnO(OH), crystallizing in

the monoclinic system (pseudo-orthorhombic).[1] Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The color is dark steel-grey to iron-black, and

the luster brilliant and submetallic. The streak is dark reddish-brown. The hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism

faces.Twinned crystals are not infrequent.

The mineral contains 89.7% manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine.

Manganite occurs with other manganese oxides in deposits formed by circulating meteoric water in the weathering environment in claydeposits and laterites. It forms by low temperature hydrothermal action in veins in association with calcite, barite, and siderite. Often associated with pyrolusite, braunite, hausmannite and goethite.[1] [4]

Manganite occurs in specimens exhibiting good crystal form at Ilfeld in the Harz Mountains of Germay, where the

mineral occurs withcalcite and barite in veins traversing porphyry. Crystals have also been found at Ilmenau in Thuringia, Neukirch near Sélestat in Alsace(newkirkite), Granam near Towie in Aberdeenshire, and in Upton

Pyne near Exeter, UK and Negaunee, Michigan, United States, and in thePilbarra of Western Australia. As an ore of manganese it is much less abundant than pyrolusite or psilomelane.

Although described with various other names as early as 1772, the name manganite was first applied in a publication by W. Haidinger in

Category Oxide mineralChemical formula MnO(OH)Strunz classification 04.FD.15

Dana 06.01.03.01

classificationIdentification

Color Dark steel-gray to black, reddish brown in transmitted light, gray-white with brownish tint, with blood-red internal reflections in reflected light

Crystal habit Slender prismatic crystals, massive to fibrousCrystal system Monoclinic, 2/m - prismatic, pseudo-orthorhombicTwinning Contact and penetration twins on {011}Cleavage {010} perfect, {110} and {001} goodFracture UnevenTenacity BrittleMohs scalehardness 4

Luster Sub-metallicStreak Reddish brown to nearly blackDiaphaneity Opaque, transparent on thin edgesSpecific gravity 4.29 - 4.34Optical properties Biaxial (+)Refractive index nα = 2.250(2) nβ = 2.250(2) nγ = 2.530(2)Birefringence δ = 0.280, Bireflectance: distinct in graysPleochroism Faint2V angle SmallDispersion Very strong

Hausmannite is a complex oxide of manganese containing both di- and tri-valent manganese. The formula can be

represented as Mn2+Mn3+2O4. It belongs to the spinel group and forms tetragonal crystals. Hausmannite is a brown to black metallic mineral with Mohs hardness of 5.5 and a specific gravity of 4.8. The type locality is

Oehrenstock (Öhrenstock), Ilmenau, Thuringian Forest, Thuringia, Germany. Locations include Batesville, Arkansas, USA; Ilfeld, Germany; Langban, Sweden; and the Ural Mountains, Russia. The best samples have been

found in South Africa and Namibia where it is associated with other manganese

oxides, pyrolusite and psilomelane and the iron-manganese mineral bixbyite.

Category Oxide mineralChemical formula Mn2+Mn3+2O4

IdentificationMolar mass 228.81Color Brownish black, Grayish.

Crystal habit Massive - Granular - Common texture observed in granite and other igneous rock. Pseudo Octahedral - Crystals show an octahedral outline.

Crystal system Tetragonal (4/m 2/m 2/m) Space Group: I 41/amdCleavage [001] PerfectFracture Uneven - Flat surfaces (not cleavage) fractured in an uneven pattern.Mohs scalehardness 5.5

Luster SubmetallicStreak dark reddish brownSpecific gravity 4.7 - 4.84, Average = 4.76Optical properties Uniaxial (-), e=2.15, w=2.46

Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its (rare) pure form, it is

typically a rose-red color, but impure specimens can be shades of pink to pale brown. The streak is white. Its Mohs hardness varies between 3.5 and 4. Itsspecific gravity is 3.5 to 3.7. It crystallizes in the trigonal system.

The cleavage is typical rhombohedral carbonate cleavage in three directions. Crystal twinning often is present. It is transparent to translucent with refractive indices of nω=1.814 to 1.816, nε=1.596 to 1.598. It is often confused with

the manganese silicate, rhodonite, but is distinctly softer.

Rhodochrosite forms a complete solid solution series with iron carbonate (siderite). Calcium, (as well

as magnesium and zinc, to a limited extent) frequently substitutes for manganese in the structure, leading to lighter shades of red and pink, depending on the degree of substitution. It is for this reason that the most common color

encountered is pink.

Rhodochrosite occurs as a hydrothermal vein mineral along with other manganese minerals in low temperature ore

deposits as in the silver mines of Romania where it was first found. Banded rhodochrosite is mined in Capillitas, Argentina. Catamarca, Argentina has an old Incan silver mine that has produced fine stalactitic examples

of rhodochrosite that are unique and very attractive. Cut cross-sections reveal concentric bands of light and dark rose colored layers. These specimens are carved and used for many ornamental purposes.[3]

Its main use is as an ore of manganese which is a key component of low-cost stainless steel formulations and certain aluminium alloys. Quality banded specimens are often used for decorative stones and jewelry. Due to its

being relatively soft, and having perfect cleaveage, it is very difficult to cut, and therefore rarely found faceted in jewelry.

It was first described in 1813 in reference to a sample from Cavnic, Maramure , present-dayş Romania. According to Dimitrescu and Radulescu, 1966 and to Papp, 1997, this mineral was described for the first time in Sacaramb,

Romania, not in Cavnic, Romania. The name is derived from the Greek word meaningῥοδόχρως rose-colored.

Colorado officially named rhodochrosite as its state mineral in 2002 based on a proposal by a local high school

(Platte Canyon High School in Bailey,Colorado). The reason for this lies in the fact that while the mineral is found

worldwide, large red crystals are found only in a few places on earth, and some of the best specimens have been

found in the Sweet Home Mine near Alma, Colorado.

The Alma King is the largest known rhodochrosite crystal; it was found in the Sweet Home Mine near Alma, Colorado. It is on display in

the Denver Museum of Nature and Science.

The Incas believed that rhodochrosite is the blood of their former rulers, turned to stone, therefore it is sometimes called "Rosa del Inca" or "Inca Rose".[4] [5]

Category Mineral speciesChemical formula MnCO3

IdentificationMolar mass 114.95 g/molColor Red to pink, Brown to yellow, gray to whiteCrystal habit Massive to well crystalineCrystal system Trigonal - HexagonalScalenohedralTwinning on the {0112} uncommonCleavage on the [1011] perfectFracture uneven, conchoidalTenacity brittleMohs scalehardness 3.5-4Luster VitreousStreak WhiteDiaphaneity Transparent to translucentDensity 3.7 g/cm³Optical properties Uniaxial (-)Birefringence δ = 0.218Pleochroism weakUltravioletfluorescence None

Rhodonite is a manganese inosilicate, (Mn, Fe, Mg, Ca)SiO3 and member of the pyroxenoid group of minerals,

crystallizing in the triclinicsystem. It commonly occurs as cleavable to compact masses with a rose-red color (the name comes from the Greek ῥόδος rhodos, rosy), often tending to brown because of surface oxidation.

Rhodonite crystals often have a thick tabular habit, but are rare. It has a perfect, prismatic cleavage, almost at right angles. The hardnessis 5.5–6.5, and the specific gravity 3.4–3.7; luster is vitreous, being less frequently pearly on

cleavage surfaces. The manganese is often partly replaced by iron, magnesium, calcium, and sometimes zinc which may sometimes be present in considerable amounts; a greyish-brown variety containing as

much as 20% of calcium oxide is called bustamite; fowlerite is a zinciferous variety containing 7% of zinc oxide.

The inosilicate (chain silicate) structure of rhodonite has a repeat unit of five silica tetrahedra. The rare

polymorph pyroxmangite, formed at different conditions of pressure and temperature, has the same chemical composition but a repeat unit of seven tetrahedra.

Rhodonite has also been worked as an ornamental stone. In the iron and manganese mines at Pajsberg near Filipstad and Långban in Värmland, Sweden, small brilliant and translucent crystals (pajsbergite) and cleavage

masses occur. Fowlerite occurs as large, rough crystals, somewhat resembling pink feldspar, with franklinite and zinc ores in granular limestone atFranklin Furnace in New Jersey.

Category Silicate mineralChemical formula (Mn2+,Fe2+,Mg,Ca)SiO3Strunz classification 09.DK.05Dana classification 65.04.01.01

IdentificationColor Rose-pink to brownish red, gray, or yellowCrystal habit Tabular crystals, massive, granularCrystal system Triclinic - Pinacoidal H-M Symbol (1) Space Group: P1Twinning Lamellar, composition plane {010}Cleavage Perfect on {110} and {110}, (110) ^ (110) = 92.5°; good on {001}Fracture Conchoidal to unevenMohs scalehardness 5.5 - 6.5Luster Vitreous to pearlyStreak White

Nikel

Batuan induk bijih nikel adalah batuan peridotit. Menurut Vinogradov batuan ultra basa rata-rata mempunyai

kandungan nikel sebesar 0,2 %. Unsur nikel tersebut terdapat dalam kisi-kisi kristal mineral olivin dan piroksin, sebagai hasil substitusi terhadap atom Fe dan Mg. Proses terjadinya substitusi antara Ni, Fe dan Mg dapat

diterangkan karena radius ion dan muatan ion yang hampir bersamaan di antara unsur-unsur tersebut. Proses serpentinisasi yang terjadi pada batuan peridotit akibat pengaruh larutan hydrothermal, akan merubah

batuan peridotit menjadi batuan serpentinit atau batuan serpentinit peroditit. Sedangkan proses kimia dan fisika dari udara, air serta pergantian panas dingin yang bekerja kontinu, menyebabkan disintegrasi dan dekomposisi

pada batuan induk.

Pada pelapukan kimia khususnya, air tanah yang kaya akan CO2 berasal dari udara dan pembusukan tumbuh-

tumbuhan menguraikan mineral-mineral yang tidak stabil (olivin dan piroksin) pada batuan ultra basa, menghasilkan Mg, Fe, Ni yang larut; Si cenderung membentuk koloid dari partikel-partikel silika yang sangat halus.

Didalam larutan, Fe teroksidasi dan mengendap sebagai ferri-hydroksida, akhirnya membentuk mineral-mineral seperti geothit, limonit, dan haematit dekat permukaan. Bersama mineral-mineral ini selalu ikut serta unsur cobalt

dalam jumlah kecil.

Larutan yang mengandung Mg, Ni, dan Si terus menerus kebawah selama larutannya bersifat asam, hingga pada

suatu kondisi dimana suasana cukup netral akibat adanya kontak dengan tanah dan batuan, maka ada kecenderungan untuk membentuk endapan hydrosilikat. Nikel yang terkandung dalam rantai silikat atau

hydrosilikat dengan komposisi yang mungkin bervariasi tersebut akan mengendap pada celah-celah atau rekahan-rekahan yang dikenal dengan urat-urat garnierit dan krisopras. Sedangkan larutan residunya akan membentuk

suatu senyawa yang disebut saprolit yang berwarna coklat kuning kemerahan. Unsur-unsur lainnya seperti Ca dan Mg yang terlarut sebagai bikarbonat akan terbawa kebawah sampai batas pelapukan dan akan diendapkan

sebagai dolomit, magnesit yang biasa mengisi celah-celah atau rekahan-rekahan pada batuan induk. Dilapangan urat-urat ini dikenal sebagai batas petunjuk antara zona pelapukan dengan zona batuan segar yang disebut

dengan akar pelapukan (root of weathering).

Faktor-faktor yang mempengaruhi pembentukan bijih nikel laterit ini adalah:

a. Batuan asal. Adanya batuan asal merupakan syarat utama untuk terbentuknya endapan nikel laterit, macam batuan asalnya adalah batuan ultra basa. Dalam hal ini pada batuan ultra basa tersebut: - terdapat elemen Ni yang

paling banyak diantara batuan lainnya - mempunyai mineral-mineral yang paling mudah lapuk atau tidak stabil,

seperti olivin dan piroksin - mempunyai komponen-komponen yang mudah larut dan memberikan lingkungan pengendapan yang baik untuk nikel.

b. Iklim. Adanya pergantian musim kemarau dan musim penghujan dimana terjadi kenaikan dan penurunan permukaan air tanah juga dapat menyebabkan terjadinya proses pemisahan dan akumulasi unsur-unsur.

Perbedaan temperatur yang cukup besar akan membantu terjadinya pelapukan mekanis, dimana akan terjadi rekahan-rekahan dalam batuan yang akan mempermudah proses atau reaksi kimia pada batuan.

c. Reagen-reagen kimia dan vegetasi. Yang dimaksud dengan reagen-reagen kimia adalah unsur-unsur dan senyawa-senyawa yang membantu mempercepat proses pelapukan. Air tanah yang mengandung CO2 memegang

peranan penting didalam proses pelapukan kimia. Asam-asam humus menyebabkan dekomposisi batuan dan dapat merubah pH larutan. Asam-asam humus ini erat kaitannya dengan vegetasi daerah. Dalam hal ini, vegetasi

akan mengakibatkan: • penetrasi air dapat lebih dalam dan lebih mudah dengan mengikuti jalur akar pohon-pohonan • akumulasi air hujan akan lebih banyak • humus akan lebih tebal Keadaan ini merupakan suatu

petunjuk, dimana hutannya lebat pada lingkungan yang baik akan terdapat endapan nikel yang lebih tebal dengan kadar yang lebih tinggi. Selain itu, vegetasi dapat berfungsi untuk menjaga hasil pelapukan terhadap erosi

mekanis.

d. Struktur. Struktur yang sangat dominan yang terdapat didaerah Polamaa ini adalah struktur kekar (joint)

dibandingkan terhadap struktur patahannya. Seperti diketahui, batuan beku mempunyai porositas dan permeabilitas yang kecil sekali sehingga penetrasi air sangat sulit, maka dengan adanya rekahan-rekahan tersebut

akan lebih memudahkan masuknya air dan berarti proses pelapukan akan lebih intensif.

e. Topografi. Keadaan topografi setempat akan sangat mempengaruhi sirkulasi air beserta reagen-reagen lain.

Untuk daerah yang landai, maka air akan bergerak perlahan-lahan sehingga akan mempunyai kesempatan untuk mengadakan penetrasi lebih dalam melalui rekahan-rekahan atau pori-pori batuan. Akumulasi andapan umumnya

terdapat pada daerah-daerah yang landai sampai kemiringan sedang, hal ini menerangkan bahwa ketebalan pelapukan mengikuti bentuk topografi. Pada daerah yang curam, secara teoritis, jumlah air yang meluncur (run off)

lebih banyak daripada air yang meresap ini dapat menyebabkan pelapukan kurang intensif.

f. Waktu. Waktu yang cukup lama akan mengakibatkan pelapukan yang cukup intensif karena akumulasi unsur

nikel cukup tinggi.

Profil nikel laterit keseluruhan terdiri dari 4 zona gradasi sebagai berikut :

1. Iron Capping : Merupakan bagian yang paling atas dari suatu penampang laterit. Komposisinya adalah akar tumbuhan, humus, oksida besi dan sisa-sisa organik lainnya. Warna khas adalah coklat tua kehitaman dan bersifat

gembur. Kadar nikelnya sangat rendah sehingga tidak diambil dalam penambangan. Ketebalan lapisan tanah penutup rata-rata 0,3 s/d 6 m. berwarna merah tua, merupakan kumpulan massa goethite dan limonite. Iron

capping mempunyai kadar besi yang tinggi tapi kadar nikel yang rendah. Terkadang terdapat mineral-mineral hematite, chromiferous.

2. Limonite Layer : Merupakan hasil pelapukan lanjut dari batuan beku ultrabasa. Komposisinya meliputi oksida besi yang dominan, goethit, dan magnetit. Ketebalan lapisan ini rata-rata 8-15 m. Dalam limonit dapat dijumpai

adanya akar tumbuhan, meskipun dalam persentase yang sangat kecil. Kemunculan bongkah-bongkah batuan beku ultrabasa pada zona ini tidak dominan atau hampir tidak ada, umumnya mineral-mineral di batuan beku basa-

ultrabasa telah terubah menjadi serpentin akibat hasil dari pelapukan yang belum tuntas. fine grained, merah coklat atau kuning, lapisan kaya besi dari limonit soil menyelimuti seluruh area. Lapisan ini tipis pada daerah yang terjal,

dan sempat hilang karena erosi. Sebagian dari nikel pada zona ini hadir di dalam mineral manganese oxide, lithiophorite. Terkadang terdapat mineral talc, tremolite, chromiferous, quartz, gibsite, maghemite.

3. Silika Boxwork : putih – orange chert, quartz, mengisi sepanjang fractured dan sebagian menggantikan zona

terluar dari unserpentine fragmen peridotite, sebagian mengawetkan struktur dan tekstur dari batuan asal. Terkadang terdapat mineral opal, magnesite. Akumulasi dari garnierite-pimelite di dalam boxwork mungkin berasal

dari nikel ore yang kaya silika. Zona boxwork jarang terdapat pada bedrock yang serpentinized.

4. Saprolite : Zona ini merupakan zona pengayaan unsur Ni. Komposisinya berupa oksida besi, serpentin sekitar

<0,4% kuarsa magnetit dan tekstur batuan asal yang masih terlihat. Ketebalan lapisan ini berkisar 5-18 m. Kemunculan bongkah-bongkah sangat sering dan pada rekahan-rekahan batuan asal dijumpai magnesit,

serpentin, krisopras dan garnierit. Bongkah batuan asal yang muncul pada umumnya memiliki kadar SiO2 dan MgO yang tinggi serta Ni dan Fe yang rendah. campuran dari sisa-sisa batuan, butiran halus limonite, saprolitic

rims, vein dari endapan garnierite, nickeliferous quartz, mangan dan pada beberapa kasus terdapat silika boxwork, bentukan dari suatu zona transisi dari limonite ke bedrock. Terkadang terdapat mineral quartz yang mengisi

rekahan, mineral-mineral primer yang terlapukkan, chlorite. Garnierite di lapangan biasanya diidentifikasi sebagai kolloidal talc dengan lebih atau kurang nickeliferous serpentin. Struktur dan tekstur batuan asal masih terlihat.

5. Bedrock : bagian terbawah dari profil laterit. Tersusun atas bongkah yang lebih besar dari 75 cm dan blok peridotit (batuan dasar) dan secara umum sudah tidak mengandung mineral ekonomis (kadar logam sudah

mendekati atau sama dengan batuan dasar). Batuan dasar merupakan batuan asal dari nikel laterit yang umumnya merupakan batuan beku ultrabasa yaitu harzburgit dan dunit yang pada rekahannya telah terisi oleh oksida besi 5-

10%, garnierit minor dan silika > 35%. Permeabilitas batuan dasar meningkat sebanding dengan intensitas serpentinisasi.Zona ini terfrakturisasi kuat, kadang membuka, terisi oleh mineral garnierite dan silika. Frakturisasi

ini diperkirakan menjadi penyebab adanya root zone yaitu zona high grade Ni, akan tetapi posisinya tersembunyi.

Garnierite is a general name for a green nickel ore which is found in pockets and veins within weathered

and serpentinized ultramafic rocks. The name was given by Jules Garnier who first described it 1864 for an occurrence in New Caledonia. It forms by lateritic weathering of ultramafic rocks and occurs in

many nickel laterite deposits in the world.

Garnierite is not a single mineral but a mixture of the Ni-Mg-

hydrosilicates serpentine, talc, sepiolite, chlorite and smectite. These minerals occur in garnierite ores individually and in intimate mixtures.

A detailed study of the garnierite ores from Falcondo Mine in the Loma Caribe serpentinized peridotites of the Dominican Republic showed that the garnierites have compositions within the three series:[1]

• Ni-bearing talc - willemseite (up to 25 wt% Ni)

• Ni-lizardite - népouite (up to 34 wt% Ni)

• Ni-sepiolite - falcondoite (up to 24 wt% Ni)

The lateritization of ultramafic rocks gives rise to a strong dissolution and removal of magnesium and silicium which

leads to a strong residual concentration of iron and nickel in a goethite-rich surface layer (nickel limonite ore). A portion of the nickel is leached downwards and finally fixed in the underlying decomposed ultramafic rock. This

process gives rise on the one hand to a moderate nickel increase of the total decomposed rock (nickel silicate, nickel saprolite); on the other hand relatively small amounts of nickel-rich garnierite ore are precipitated in hollow

spaces.

A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene.

Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron. Peridotite is derived from the Earth's mantle, either as

solid blocks and fragments, or as crystals accumulated from magmas that formed in the mantle. The compositions of peridotites from these layered igneous complexes vary widely, reflecting the relative proportions

ofpyroxenes, chromite, plagioclase, and amphibole.

Peridotite is the dominant rock of the upper part of the Earth's mantle. The compositions of peridotite nodules found

in certain basalts and diamond pipes (kimberlites) are of special interest, because they provide samples of the Earth's Mantle roots of continents brought up from depths from about 30 km or so to depths at least as great as

about 200 km. Some of the nodules preserve isotope ratios of osmium and other elements that record processes over three billion years ago, and so they are of special interest to paleogeologists because they provide clues to the

composition of the Earth's early mantle and the complexities of the processes that were involved.

IRON ORE

Biji atau bijih besi adalah cebakan yang digunakan untuk membuat besi gubal.

Biji besi terdiri atas oksigen dan atom besi yang berikatan bersama dalam molekul. Besi sendiri biasanya didapatkan dalam bentuk magnetit (Fe3O4), hematit(Fe2O3), goethit, limonit atau siderit. Bijih besi biasanya kaya

akan besi oksida dan beragam dalam hal warna, dari kelabu tua, kuning muda, ungu tua, hingga merah karat.

Saat ini, cadangan biji besi nampak banyak, namun seiring dengan bertambahnya penggunaan besi secara

eksponensial berkelanjutan, cadangan ini mulai berkurang, karena jumlahnya tetap. Sebagai contoh, Lester Brown dari Worldwatch Institute telah memperkirakan bahwa bijih besi bisa habis dalam waktu 64 tahun

berdasarkan pada ekstrapolasi konservatif dari 2% pertumbuhan per tahun.

Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of

the spinel group. The chemical IUPAC name is iron(II,III) oxide and the common chemical name ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part wüstite (FeO) and one

part hematite (Fe2O3). This refers to the different oxidation states of the iron in one structure, not a solid solution.

The Curie temperature of magnetite is 858 K (585 °C; 1,085 °F).

Magnetite is the most magnetic of all the naturally occurring minerals on Earth.[4] Naturally magnetized pieces of

magnetite, calledlodestone, will attract small pieces of iron, and this was how ancient man first discovered the property of magnetism. Lodestone was used as an early form of magnetic compass. Magnetite typically carries the

dominant magnetic signature in rocks, and so it has been a critical tool in paleomagnetism, a science important in discovering and understanding plate tectonics and as historic data formagnetohydrodynamics and other scientific

fields. The relationships between magnetite and other iron-rich oxide minerals such asilmenite, hematite, and ulvospinel have been much studied, as the complicated reactions between these minerals

and oxygen influence how and when magnetite preserves records of the Earth's magnetic field.

Magnetite has been very important in understanding the conditions under which rocks form and evolve. Magnetite

reacts with oxygen to produce hematite, and the mineral pair forms a buffer that can control oxygen fugacity. Commonly igneous rocks contain grains of two solid solutions, one between magnetite and ulvospinel and the other

between ilmenite and hematite. Compositions of the mineral pairs are used to calculate how oxidizing was the magma (i.e., the oxygen fugacity of the magma): a range of oxidizing conditions are found in magmas and the

oxidation state helps to determine how the magmas might evolve by fractional crystallization.

Small grains of magnetite occur in almost all igneous rocks and metamorphic rocks. Magnetite also occurs in

many sedimentary rocks, including banded iron formations. In many igneous rocks, magnetite-rich and ilmenite-rich grains occur that precipitated together from magma. Magnetite also is produced

from peridotites and dunites by serpentinization.

Magnetite is a valuable source of iron ore. It dissolves slowly in hydrochloric acid.

Magnetite is sometimes found in large quantities in beach sand. Such black sands (mineral sands or iron sands) are found in various places such as California and the west coast of New Zealand. The magnetite is carried to the

beach via rivers from erosion and is concentrated via wave action and currents.

Huge deposits have been found in banded iron formations. These sedimentary rocks have been used to infer

changes in the oxygen content of the atmosphere of the Earth.

Large deposits of magnetite are also found in the Atacama region of Chile, Kiruna, Sweden, thePilbara, Midwest

and Northern Goldfields regions in Western Australia, and in the Adirondack region of New York in the United States. Deposits are also found in Norway, Germany, Italy, Switzerland,South Africa, India, Mexico, and

in Oregon, New Jersey, Pennsylvania, North Carolina, Virginia,New Mexico, Utah, and Colorado in the United

States. In 2005 an exploration company, Cardero Resources, discovered a vast deposit of magnetite-bearing sand dunes in Peru. The dune field covers 250 square kilometers (100 sq mi), with the highest dune at over 2,000

meters (6,560 ft) above the desert floor. The sand contains 10% magnetite

Category Oxide mineral Spinel groupChemical formula iron(II,III) oxide, Fe3O4Crystal symmetry Isometric 4/m 3 2/mUnit cell a = 8.397 Å; Z=8

IdentificationColor Black, gray with brownish tint in reflected lightCrystal habit Octahedral, fine granular to massiveCrystal system Isometric HexoctahedralTwinning On {Ill} as both twin and composition plane, the spinel law, as contact twinsCleavage Indistinct, parting on {Ill}, very goodFracture UnevenTenacity BrittleMohs scalehardness 5.5–6.5Luster MetallicStreak BlackDiaphaneity OpaqueSpecific gravity 5.17–5.18

Hematite, also spelled as hæmatite, is the mineral form of iron(III) oxide (Fe2O3), one of several iron oxides.

Hematite crystallizes in therhombohedral system, and it has the same crystal structure as ilmenite and corundum. Hematite and ilmenite form a complete solid solution at temperatures above 950°C.

Hematite is a mineral, colored black to steel or silver-gray, brown to reddish brown, or red. It is mined as the main ore of iron. Varieties include kidney ore, martite (pseudomorphs after magnetite), iron

rose and specularite (specular hematite). While the forms of hematite vary, they all have a rust-red streak. Hematite is harder than pure iron, but much more brittle. Maghemite is a hematite- and magnetite-related oxide mineral.

Huge deposits of hematite are found in banded iron formations. Grey hematite is typically found in places where there has been standing water or mineral hot springs, such as those in Yellowstone National Park in the United

States. The mineral can precipitate out of water and collect in layers at the bottom of a lake, spring, or other standing water. Hematite can also occur without water, however, usually as the result of volcanic activity.

Clay-sized hematite crystals can also occur as a secondary mineral formed by weathering processes in soil, and along with other iron oxides or oxyhydroxides such as goethite, is responsible for the red color of many tropical,

ancient, or otherwise highly weathered soils.

Good specimens of hematite come from England, Mexico, Brazil, Australia, United States and Canada.

Category Oxide mineralChemical formula iron(III) oxide, Fe2O3, α-Fe2O3

IdentificationColor Metallic gray to earthy red tonesCrystal habit Tabular to thick crystalsCrystal system Trigonal - hexagonal scalenohedralCleavage None

Fracture Uneven to sub-conchoidalMohs scalehardness 5.5 - 6.5Luster Metallic to splendentStreak Bright red to dark redSpecific gravity 4.9 - 5.3Refractive index OpaquePleochroism None

Goethite (FeO(OH)), (pronounced /ˈɡɜrtaɪt/ "gertite") named after the German polymath Johann Wolfgang von

Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment

samples taken from the caves of Lascaux inFrance. It was first described in 1806 for occurrences in the Mesabi iron ore district ofMinnesota. Recently, nanoparticulate authigenic goethite was shown to be the most

commondiagenetic iron oxyhydroxide in both marine and lake sediments

Category MineralChemical formula α-Fe O (OH)

IdentificationColor Yellowish to reddish to dark brownCrystal system Orthorhombic 2/m2/m2/mCleavage Perfect 010Fracture uneven to splinteryMohs scalehardness 5 - 5.5Luster adamantine to dullStreak brown, brownish yellow to orange yellow

Specific gravity 3.3 - 4.3Refractive index Opaque to sub-translucentFusibility Fusible at 5 - 5.5Other characteristics Becomes magnetic in reducing flame

Limonite is an ore consisting in a mixture of hydrated iron(III) oxide-hydroxide of varying composition. The generic

formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide.

Together with hematite, it has been mined as ore for the production of iron. Limonite is heavy and yellowish-brown. It is a very common amorphous substance though can be tricky to find when mined with hematite and bog ore.

It is not a true mineral and it is composed by a mixture of similar hydrated iron oxide minerals, mostly goethite with lepidocrocite, jarosite, and others. Limonite forms mostly in or near oxidized iron and other

metal ore deposits and as sedimentary beds. Limonite may occur as the cementing material in iron rich sandstones. Also known as the Lemon Rock.

It is never crystallized into macroscopic crystals, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms or in compact and earthy masses; sometimes mammillary, botryoidal,

reniform or stalactitic. The colour presents various shades of brown and yellow, and the streak is always brownish, a character which distinguishes it from hematite with a red, or from magnetite with a black streak. It is sometimes

called brown hematite or brown iron ore.

Limonite has been known to form pseudomorphs after other minerals such as pyrite, meaning that the chemical

weathering transforms the crystal of pyrite into limonite but keeps the external shape of the pyrite crystal. It has also been formed from other iron oxides, hematite and magnetite; the carbonate siderite and iron rich silicates like

some garnets.

It is named from the Greek word for meadow ( ), in allusion to its occurrence as "λειμών bog-ore"

in meadows and marshes.

The hardness is variable, but generally in the 4 - 5.5 range. The specific gravity varies from 2.9 to 4.3.

Siderite is a mineral composed of iron carbonate Fe C O 3. It takes its name from the Greek word

σίδηρος sideros, “iron . It is a valuable iron mineral, since it is 48% iron and contains no” sulfur or phosphorus.

Both magnesium and manganese commonly substitute for the iron.

Siderite has Mohs hardness of 3.5-4, a specific gravity of 3.8, a white streak and a vitreous lustre or pearly luster.

Its crystals belong to the hexagonal system, and are rhombohedral in shape, typically with curved and striated faces. It also occurs in masses. Color ranges from yellow to dark brown or black, the latter being due to the

presence of manganese (sometimes called manganosiderite).

Siderite is commonly found in hydrothermal veins, and is associated with barite, fluorite, galena, and others. It is

also a common diageneticmineral in shales and sandstones, where it sometimes forms concretions. In sedimentary rocks, siderite commonly forms at shallow burial depths and its elemental composition is often related to

the depositional environment of the enclosing sediments.[4] In addition, a number of recent studies have used the oxygen isotopic composition of sphaerosiderite (a type associated with soils) as a proxy for

the isotopiccomposition of meteoric water shortly after deposition.[5]

Category Carbonate mineralChemical formula FeCO3Strunz classification 05.AB.05Dana classification 14.01.01.03

Identification

Color Pale yellow to tannish, grey, brown, green, red, black and sometimes nearly colorless

Crystal habit Tabular crystals, often curved - botryoidal to massiveCrystal system Trigonal - Hexagonal scalenohedral (3 2/m)Twinning Lamellar uncommon on{0112}Cleavage Perfect on on{0111}Fracture Uneven to conchoidalTenacity BrittleMohs scalehardness 3.75 - 4.25Luster Vitreous, may be silky to pearlyStreak WhiteDiaphaneity Translucent to subtranslucentSpecific gravity 3.5Optical properties Uniaxial (-)Refractive index nω = 1.875 nε = 1.633Birefringence δ = 0.242Dispersion Strong

Bijih

Bijih adalah sejenis batu yang mengandung mineral penting, baik itu logam maupun bukan logam. Bijih diekstraksi melalui penambangan, kemudian hasilnya dimurnikan lagi untuk mendapatkan unsur-unsur yang

bernilai ekonomis.

Kandungan atau kadar mineral, atau logam, juga bentuk keujudannya, secara langsung akan memengaruhi ongkos

pertambangan bijih. Ongkos ekstraksi harus diberi pembobotan untuk dibandingkan dengan nilai ekonomis logam yang terkandung untuk menentukan bijih yang mana yang lebih menguntungkan dan bijih yang mana yang kurang

atau tidak menguntungkan. Bijih logam secara umum merupakan persenyawaan oksida, sulfida, silikat, atau logam "murni" (misalnya tembaga murni yang biasanya tidak terkumpul di dalam kerak Bumi atau logam "mulia" (biasanya

tidak berbentuk persenyawaan) seperti emas. Bijih harus diolah untuk mengekstraksi logam-logam dari "batuan sampah" dan dari mineral bijih. Tubuh bijih dibentuk oleh berbagai macam proses geologis. Di dalam bahasa

Inggris, proses "pembentukan bijih" disebut sebagai ore genesis.

Proses terbentuknya bijih sangatlah kompleks. Sering lebih dari satu proses bekerja bersama-sama. Meskipun dari

satu jenis bijih, apabila terbentuk oleh proses yang berbeda-beda, maka akan menghasilkan tipe endapan yang berbeda-beda pula.

Penggolongan bijih menurut pembentukannya

1. bijih primer (hipogen), yakni bijih yang diendapkan pada saat terjadinya proses pelogaman2. bijih sekunder (supergen), yakni bijih yang diendapkan sebagai akibat alterasi dari bijih primer, oleh proses

pelapukan dari air permukaan yang meresap ke dalam tanah.Proses pembentukan

1. Konsentrasi magmatik > deposit magmatik

2. Sublimasi > sublimat3. Kontak metasomatisme > deposit kontak metasomatik

4. Konsentrasi hidrotermal > pengisian celah-celah terbuka (pertukaran ion pada batuan)5. Sedimentasi lapisan sedimenter (evaporit)

6. Pelapukan Konsentrasi residual7. Metamorfisme > deposit metamorfik

8. Hidrologi > air tanah

Contoh proses pengendapan bijih besi

1. Diferensiasi magmatik

2. Larutan hidrotermal3. Proses sedimentasi

4. Proses pelapukanKategorisasi endapan bijih besi

1. Mutu

2. Besar cadangan3. Jenis mineral ikutan

Manfaat pengenalan proses pembentukan

1. Membantu dalam proses pencarian2. Membantu dalam proses penemuan

3. Membantu dalam proses pengembangan bahan galian

Cadangan bijih

"Cadangan bijih" atau "cebakan bijih" adalah timbunan bijih pada satu kawasan yang ditentukan batas-batasnya. Ini

berbeda dengan sumber daya mineral yang didefinisikan menurut kriteria penggolongan sumber daya mineral. Cadangan bijih adalah kenampakan satu jenis bijih tertentu. Sebagian besar cadangan bijih dinamai menurut

lokasinya (misalnya, Witswatersrand, Afrika Selatan), atau menurut penemunya (misalnya cadangan nikel kambalda dinamakan menurut pengebor perintisnya), atau menurut lelucon, tokoh sejarah, tokoh terkemuka,

mitologi (phoenix, kraken, serepentleopard, dll) atau nama sandi perusahaan sumber daya yang mendirikannya (misalnya MKD-5 adalah nama singkatan untuk perusahaan tambang nikel Mount Keith).

Cadangan bijih digolongkan menurut bermacam-macam kriteria yang dikembangkan melalui pengkajian geologi ekonomi, atau pembentukan bijih. Berikut ini adalah penggolongan yang biasa dilakukan.

Cadangan epigenetik hidrotermal

• Cadangan emas lapisan mesotermal, misalnya Golden Mile, Kalgoorlie, Australia Barat.

• Konglomerat arkean yang mengandung cadangan emas-uranium, misalnya Elliot Lake, Kanada,

dan Witwatersrand, Afrika Selatan

• Cadangan emas jenis Carlin, meliputi;

• Subjenis penggantian jasperoid yang mengandung dolomit

• Cadangan lorong mineral stockwork epitermalHidrotermal terkait granit

• IOCG atau cadangan besi oksida tembaga emas, yang dicirikan oleh adanya cadangan Cu-Au-U Olympic

Dam super-raksasa di Australia Selatan

• Cadangan tembaga porfiri +/- emas +/- molibdenum +/- perak

• Tembaga-emas terkait-intrusif +/- (timah-tungsten), yang dicirikan oleh adanya cadangan Tombstone,

Arizona

• Cadangan bijih besi magnetit hidromagmatik dan skarn

• Cadangan bijih skarn dari tembaga, timbal, seng, tungsten, dllCadangan nikel-kobalt-platina

• Cadangan nikel-tembaga-besi-PGE magmatik meliputi

• Batuan kumulat vanadifer atau kromit atau magnetit yang mengandung platina

• Cadangan titanium batuan-keras kumulat (ilmenit)

• Cadangan komatiit yang mengandung Ni-Cu-PGE

• Subjenis pemuat batuan subvolkanik, yang dicirikan oleh Noril'sk-Talnakh dan Thompson

Belt, Kanada

• Ni-Cu-PGE terkait-intrusif, yang dicirikan oleh Voisey's Bay, Kanada, dan Jinchuan, Republik

Rakyat Cina

• Cadangan bijih nikel lateritik, contohnya meliputi Goro dan Acoje, (Filipina) dan Ravensthorpe, Australia

Barat.Cadangan terkait gunung berapi

• Sulfida massif gunung berapi (VHMS) Cu-Pb-Zn meliputi;

• Contohnya adalah Teutonic Bore dan Golden Grove, Western Australia

• Jenis Besshi

• Jenis Kuroko

Cadangan metamorfik

• Cadangan besi oksida-kromit serpenitit podiforma, yang dicirikan oleh bijih besi Savage River, Tasmania,

cadangan kromit Coobina

• Pb-Zn-Ag jenis Broken Hill, dipandang sebagai kelas dari cadangan SEDEX yang digarap-ulangTerkait batuan beku karbonatit-alkali

• Fosfor-tantalit-vermikulit (Phalaborwa Afrika Selatan)

• Unsur langka bumi - Mount Weld, Australia dan Bayan Obo, Mongolia

• Diatrem yang mengandung berlian pada kimberlit, lamproit, atau lamprofirCadangan endapan

Potret-dekat sampel formasi besi terikat dari Michigan Hulu. Batang skala adalah 5,0 mm.

• Cadangan bijih besi formasi besi terikat, meliputi

• Cadangan kanal-besi atau bijih besi jenis pisolit

• Cadangan bijih pasir mineral berat dan bukit pasir yang mengandung cadangan lainnya

• Cadangan aluvial emas, berlian, timah, platina, atau pasir hitam

• Jenis cadangan seng aluvial: misalnya Seng SkorpionCadangan hidrotermal endapan

• SEDEX

• Timbal-seng-perak, yang dicirikan oleh Red Dog, McArthur River, Mount Isa, dll

• Stratiforma yang mengandung arkosa dan serpih tembaga, yang dicirikan oleh sabuk tembaga

Zambia.

• Stratiforma tungsten, yang dicirikan oleh cadangan Erzgebirge, Cekoslowakia

• Cadangan emas yang dikandung oleh rijang-spilit ekshalatif hosted gold deposits

• Cadangan seng-timbal jenis lembah Mississippi (MVT)

• Cadangan bijih besi hematit dari formasi besi terikatBijih terkait astroblema

• Tembaga dan nikel Cekungan Sudbury, Ontario, Kanada

Ekstraksi dasar cadangan bijih mengikuti tahapan-tahapan berikut ini;

1. Prospekting atau eksplorasi untuk menentukan dan kemudian mendefinisikan keluasan dan nilai bijih

tempat di mana ia berada ("tubuh bijih")2. Menjalankan penaksiran sumber daya untuk menaksir secara matematika ukuran dan kadar cadangan

3. Menjalankan pengkajian pra-kelayakan untuk menentukan keekonomian cadangan bijih secara teoretis. Tindakan ini mengenali secara dini, apakah penanaman modal lanjutan untuk pengkajian penaksiran dan

teknis dapat dijamin secara aman atau tidak, dan mengenali risiko dan wilayah kunci untuk pengerjaan

selanjutnya.4. Menjalankan studi kelayakan untuk menilai kesinambungan dana, risiko teknis dan keuangan, dan

kesehatan projek dan membuat keputusan apakah projek pertambangan yang diajukan dapat diteruskan atau dihentikan. Ini meliputi perencanaan penambangan untuk menilai porsi keterpulihan ekonomi

cadangan, metalurgi dan bijih, kelayakan penjualan dan keterbayaran konsentrat bijih, biaya-biaya teknik, penggilingan, dan infrastruktur, persyaratan keuangan dan ketergulirannya, dan lokasi sampel untuk

menganalisis tambang yang mungkin dilakukan, dari penggalian awal melalui reklamasi.5. Pengembangan untuk menciptakan akses ke tubuh bijih dan bangunan instalasi pertambangan dan

peralatannya6. Operasi pertambangan yang sebenarnya7. Reklamasi untuk membuat tanah bekas pertambangan dapat dimanfaatkan di masa depan

Bijih (logam) diperdagangkan secara internasional dan memberikan porsi yang cukup berarti di dalam

perdagangan internasional bahan-bahan mentah, baik itu secara nilai ekonomisnya maupun jumlah fisiknya. Ini disebabkan oleh sebaran bijih di dunia tidaklah seragam, di satu pihak kaya akan bijih tetapi miskin fasilitas

pengolahannya, sedangkan di pihak lain miskin akan bijih tetapi kaya akan fasilitas pengolahannya.

Sebagian besar logam dasar (tembaga, timbal, seng, nikel) diperdagangkan secara internasional di Bursa Logam

London, dengan persediaan dan pertukaran logam yang lebih minimalis yang dipantau oleh Bursa Merkantil New York di Amerika Serikat dan Bursa Masa Depan Shanghai di Republik Rakyat Cina.

Bijih besi diperdagangkan antara konsumen dan produsen, meskipun bermacam-macam harga tolok ukur ditentukan tahunan antara konglomerat pertambangan utama dan konsumen utama, dan ini mengatur wadah bagi

partisipan yang lebih sedikit.

Komoditas lain yang lebih sedikit tidak memiliki gedung-gedung kliring dan harga tolok ukur, dengan sebagian

besar harga dinegosiasikan antara pemasok dan konsumen, secara berhadapan langsung. Ini secara umum membuat penentuan harga bijih menjadi lebih sulit dan kabur. Logam-logam itu misalnya litium, niobium-

tantalum, bismut, antimon, dan unsur langka. Sebagian besar komoditas ini juga didominasi oleh satu atau dua pemasok utama dengan lebih dari 60% cadangan dunia. Bursa Logam London menambahkan uranium ke dalam

daftar logam yang diberi jaminan.

Bank Dunia melaporkan bahwa Cina adalah pengimpor terbesar bijih dan logam pada tahun 2005 diikuti oleh

Amerika Serikat dan Jepang.

Mineral bijih penting

• Argentit: Ag2S untuk menghasilkan perak

• Barit: BaSO4

• Bauksit Al2O3 untuk menghasilkan aluminium

• Beril: Be3Al2(SiO3)6• Bornit: Cu5FeS4

• Kasiterit: SnO2

• Kalkosit: Cu2S untuk menghasilkan tembaga

• Kalkopirit: CuFeS2

• Kromit: (Fe, Mg)Cr2O4 untuk menghasilkan kromium

• Sinabar: HgS untuk menghasilkan Raksa

• Kobaltit: (Co, Fe)AsS

• Kolumbit-Tantalit atau Koltan: (Fe, Mn)(Nb, Ta)2O6

• Galena: PbS

• Emas: Au, biasanya berserikat dengan kuarsa atau sebagai cadangan utama

• Hematit: Fe2O3

• Ilmenit: FeTiO3

• Magnetit: Fe3O4

• Molibdenit: MoS2

• Pentlandit:(Fe, Ni)9S8

• Pirolusit:MnO2

• Skeelit: CaWO4

• Sfalerit: ZnS

• Uraninit: UO2 untuk menghasilkan uranium

• Wolframit: (Fe, Mn)WO4

•

Mineral resource classification is the classification of mineral deposits based on their geologic certainty and economic value.

A "McKelvey diagram" showing the relationship of mineral resource classifications to economics and geologic certainty.[1]

Mineral deposits can be classified as:

• Mineral occurrences or prospects of geological interest but not necessarily of economic interest

• Mineral resources that are potentially valuable, and for which reasonable prospects exist for eventual economic extraction.

• Mineral reserves or Ore reserves that are valuable and legally and economically and technically feasible to extract

In common mining terminology, an "ore deposit" by definition must have an 'ore reserve', and may or may not have additional 'resources'.

Classification, because it is an economic function, is governed by statutes, regulations and industry best practice norms. There are several classification schemes worldwide, however the Canadian CIM classification

(see NI 43-101), the Australasian Joint Ore Reserves Committee Code (JORC Code), and the South African Code for the Reporting of Mineral Resources and Mineral Reserves (SAMREC)[2] are the general standards.

Mineral occurrences, prospects

Main article: mineral exploration

These classifications of mineral occurrences are generally the least important and least economic. They include all known occurrences of minerals of economic interest, including obviously uneconomic outcrops and manifestations.

However, these are often mentioned in a company prospectus because of "proximity"; a concept that something valuable may be found near these occurrences because it has been in the past due to a similar geological

environment. Often, such occurrences of mineralisation are the peripheral manifestations of nearby ore deposits. "Ore deposit" applies specifically to economic mineral occurrences that could be mined at a profit after

consideration of all factors impacting a mining operation. Note that this distinction between amounts of raw material

available as either a resource or reserve also applies to other materials considered to be minerals. This can include

natural gas (legally defined as a mineral in some states of the United States) and hydrocarbons.

Mineral resources

Mineral resources are those economic mineral concentrations that have undergone enough scrutiny to quantify

their contained metal to a certain degree. None of these resources are ore, because the economics of the mineral deposit may not have been fully evaluated.

Indicated resources are simply economic mineral occurrences that have been sampled (from locations such as outcrops, trenches, pits and drillholes) to a point where an estimate has been made, at a reasonable level of

confidence, of their contained metal, grade, tonnage, shape, densities, physical characteristics[3].

Measured resources are indicated resources that have undergone enough further sampling that a 'competent

person' (defined by the norms of the relevant mining code; usually ageologist) has declared them to be an acceptable estimate, at a high degree of confidence, of the grade, tonnage, shape, densities, physical

characteristics and mineral content of the mineral occurrence.

Resources may also make up portions of a mineral deposit classified as a mineral reserve, but:

• Have not been sufficiently drilled out to qualify for Reserve status; or

• Have yet to meet all criteria for Reserve status [3]

Mineral reserves

Mineral reserves are resources known to be economically feasible for extraction. Reserves are either Probable Reserves or Proven Reserves. Generally the conversion of resources into reserves requires the application of

various modifying factors, including:

• mining and geological factors, such as knowledge of the geology of the deposit sufficient that it is

predictable and verifiable; extraction and mine plans based on ore models; quantification of geotechnical risk— basically, managing the geological faults, joints, and ground fractures so the mine does not collapse;

and consideration of technical risk— essentially, statistical and variography to ensure the ore is sampled properly:

• metallurgical factors, including scrutiny of assay data to ensure accuracy of the information supplied by

the laboratory— required because ore reserves are bankable. Essentially, once a deposit is elevated to

reserve status, it is an economic entity and an asset upon which loans and equity can be drawn— generally to pay for its extraction at (hopefully) a profit;

• economic factors;• environmental factors;

• marketing factors;• legal factors;

• governmental factors;and

• social factors [4].

Further information

• JORC Code

• University of Western Australia Mining Law Centre

• U.S. Geological Survey Circular 831, Principles of a Resource/Reserve Classification for Minerals

• Canadian Institute of Mining, Metallurgy and Petroleum - CIM Definition Standards - On Mineral Resources

and Mineral Reserves (PDF Format)

• The Canadian Council of Professional Geoscientists CCPG

• NI 43-101 Guidelines

• The South African SAMVAL and SAMREC Codes

Ore Genesis

The various theories of ore genesis explain how the various types of mineral deposits form within the Earth's crust.

Ore genesis theories are very dependent on the mineral or commodity.

Ore genesis theories generally involve three components: source, transport or conduit, and trap. This also applies

to the petroleum industry, which was first to use this methodology.

• Source is required because metal must come from somewhere, and be liberated by some process

• Transport is required first to move the metal bearing fluids or solid minerals into the right position, and refers to the act of physically moving the metal, as well as chemical or physical phenomenon which

encourage movement

• Trapping is required to concentrate the metal via some physical, chemical or geological mechanism into a

concentration which forms mineable ore

The biggest deposits are formed when the source is large, the transport mechanism is efficient, and the trap is

active and ready at the right time.

Evans (1993) divides ore genesis into the following main categories based on physical process. These are internal

processes, hydrothermal processes, metamorphic processes and surficial processes.

Internal processes

These processes are integral physical phenomena and chemical reactions internal to magmas, generally

in plutonic or volcanic rocks. These include;

• Fractional crystallization, either creating monominerallic cumulate ores or contributing to the enrichment of

ore minerals and metals

• Liquation, or liquid immiscibility between melts of differing composition, usually sulfide segregations of

nickel-copper-platinoid sulfides and silicates.

Hydrothermal processes

These processes are the physico-chemical phenomena and reactions caused by movement of hydrothermal waters

within the crust, often as a consequence of magmatic intrusion or tectonic upheavals. The foundations of hydrothermal processes are the source-transport-trap mechanism.

Sources of hydrothermal solutions include seawater and meteoric water circulating through fractured rock, formational brines (water trapped within sediments at deposition) and metamorphic fluids created by dehydration of

hydrous minerals during metamorphism.

Metal sources may include a plethora of rocks. However most metals of economic importance are carried as trace

elements within rock-forming minerals, and so may be liberated by hydrothermal processes. This happens because of:

• incompatibility of the metal with its host mineral, for example zinc in calcite, which favours aqueous fluids in

contact with the host mineral during diagenesis.

• solubility of the host mineral within nascent hydrothermal solutions in the source rocks, for example mineral

salts (halite), carbonates (cerussite), phosphates (monazite andthorianite) and sulfates (barite)

• elevated temperatures causing decomposition reactions of minerals

Transport by hydrothermal solutions usually requires a salt or other soluble species which can form a metal-bearing

complex. These metal-bearing complexes facilitate transport of metals within aqueous solutions, generally as hydroxides, but also by processes similar to chelation.

This process is especially well understood in gold metallogeny where various thiosulfate, chloride and other gold-carrying chemical complexes (notably tellurium-chloride/sulfate or antimony-chloride/sulfate). The majority of metal

deposits formed by hydrothermal processes include sulfide minerals, indicating sulfur is an important metal-carrying complex.

Sulfide deposition:Sulfide deposition within the trap zone occurs when metal-carrying sulfate, sulfide or other complexes become

chemically unstable due to one or more of the following processes;

• falling temperature, which renders the complex unstable or metal insoluble

• loss of pressure, which has the same effect

• reaction with chemically reactive wall rocks, usually of reduced oxidation state, such as iron bearing

rocks, mafic or ultramafic rocks or carbonate rocks• degassing of the hydrothermal fluid into a gas and water system, or boiling, which alters the metal carrying

capacity of the solution and even destroys metal-carrying chemical complexes

Metal can also become precipitated when temperature and pressure or oxidation state favour different ionic

complexes in the water, for instance the change from sulfide to sulfate, oxygenfugacity, exchange of metals between sulfide and chloride complexes, et cetera.

Metamorphic processes

Lateral secretion:

Ore deposits formed by lateral secretion are formed by metamorphic reactions during shearing, which liberate mineral constituents such as quartz, sulfides, gold, carbonates and oxides from deforming rocks and focus these

constituents into zones of reduced pressure or dilation such as faults. This may occur without much hydrothermal fluid flow, and this is typical of podiform chromite deposits.

Metamorphic processes also control many physical processes which form the source of hydrothermal fluids, outlined above.

Surficial processes

Surficial processes are the physical and chemical phenomena which cause concentration of ore material within the regolith, generally by the action of the environment. This includesplacer deposits, laterite deposits and residual

or eluvial deposits. The physical processes of ore deposit formation in the surficial realm include;

• erosion

• deposition by sedimentary processes, including winnowing, density separation (e.g.; gold placers)

• weathering via oxidation or chemical attack of a rock, either liberating rock fragments or creating chemically

deposited clays, laterites or manto ore deposits

• Deposition in low-energy environments in beach environments

Classification of ore deposits

Ore deposits are usually classified by ore formation processes and geological setting. For example, SEDEX deposits, literally meaning "sedimentary exhalative" are a class of ore deposit formed on the sea

floor (sedimentary) by exhalation of brines into seawater (exhalative), causing chemical precipitation of ore minerals when the brine cools, mixes with sea water and loses its metal carrying capacity.

Ore deposits rarely fit snugly into the boxes in which geologists wish to place them. Many may be formed by one or more of the basic genesis processes above, creating ambiguous classifications and much argument and

conjecture. Often ore deposits are classified after examples of their type, for instance Broken Hill Type lead-zinc-silver deposits or Carlin–type gold deposits.

Classification of hydrothermal ore deposits is also achieved by classifying according to the temperature of formation, which roughly also correlates with particular mineralising fluids, mineral associations and structural

styles. This scheme, proposed by Waldemar Lindgren (1933) classified hydrothermal deposits as hypothermal, mesothermal, epithermal andtelethermal.

Genesis of common ores

This page has been organised by metal commodity; it is also possible to organise theories according to geological criteria of formation, as well as by metal association. Often ores of the same metal can be formed by

multiple processes, and this is described by commodity.

Iron

Main article: Iron ore

Iron ores are overwhelmingly derived from ancient sediments known as banded iron formations (BIFs). These sediments are composed of iron oxide minerals deposited on the sea floor. Particular environmental conditions are

needed to transport enough iron in sea water to form these deposits, such as acidic and oxygen-poor atmospheres within the Proterozoic Era.

Often, more recent weathering during the Tertiary or Eocene is required to convert the usual magnetite minerals

into more easily processed hematite. Some iron deposits within thePilbara of West Australia are placer deposits, formed by accumulation of hematite gravels called pisolites which form channel-iron deposits. These are preferred

because they are cheap to mine.

Lead zinc silver

Main article: Sedimentary exhalative deposits

Main article: Carbonate hosted lead zinc ore depositsMain article: Volcanogenic massive sulfide ore deposit

Lead-zinc deposits are generally accompanied by silver, hosted within the lead sulfide mineral galena or within the zinc sulfide mineral sphalerite.

Lead and zinc deposits are formed by discharge of deep sedimentary brine onto the sea floor (termed sedimentary exhalative or SEDEX), or by replacement of limestone, in skarndeposits, some associated with submarine

volcanoes (called volcanogenic massive sulfide ore deposits or VMS) or in the aureole of subvolcanic intrusions of granite. The vast majority of SEDEX lead and zinc deposits are Proterozoic in age, although there are significant

Jurassic examples in Canada and Alaska.

The carbonate replacement type deposit is exemplified by the Mississippi valley type (MVT) ore deposits. MVT and

similar styles occur by replacement and degradation of carbonate sequences by hydrocarbons, which are thought important for transporting lead.

Gold

Gold deposits are formed via a very wide variety of geological processes. Deposits are classified as primary, alluvial or placer deposits, or residual or laterite deposits. Often a deposit will contain a mixture of all three types of

ore.

Plate tectonics is the underlying mechanism for generating gold deposits. The majority of primary gold deposits fall

into two main categories: lode gold deposits or intrusion-related deposits.

Lode gold deposits are generally high-grade, thin, vein and fault hosted. They are primarily made up of quartz veins

also known as lodes or reefs, which contain either native gold or goldsulfides and tellurides. Lode gold deposits are usually hosted in basalt or in sediments known as turbidite, although when in faults, they may occupy intrusive

igneous rocks such asgranite.

Lode-gold deposits are intimately associated with orogeny and other plate collision events within geologic history.

Most lode gold deposits sourced from metamorphic rocks because it is thought that the majority are formed by dehydration of basalt during metamorphism. The gold is transported up faults by hydrothermal waters and

deposited when the water cools too much to retain gold in solution.

Intrusive related gold (Lang & Baker, 2001) is generally hosted in granites, porphyry or rarely dikes. Intrusive

related gold usually also contains copper, and is often associated with tinand tungsten, and rarely molybdenum, antimony and uranium. Intrusive-related gold deposits rely on gold existing in the fluids

associated with the magma (White, 2001), and the inevitable discharge of these hydrothermal fluids into the wall-rocks (Lowenstern, 2001). Skarn deposits are another manifestation of intrusive-related deposits.

Placer deposits are sourced from pre-existing gold deposits and are secondary deposits. Placer deposits are formed by alluvial processes within rivers, streams and on beaches. Placer gold deposits form via gravity, with

the density of gold causing it to sink into trap sites within the river bed, or where water velocity drops, such as bends in rivers and behind boulders. Often placer deposits are found within sedimentary rocks and can be billions

of years old, for instance the Witwatersrand deposits in South Africa. Sedimentary placer deposits are known as

'leads' or 'deep leads'.

Placer deposits are often worked by fossicking, and panning for gold is a popular pastime.

Laterite gold deposits are formed from pre-existing gold deposits (including some placer deposits) during prolonged weathering of the bedrock. Gold is deposited within iron oxides in the weathered rock or regolith, and may be

further enriched by reworking by erosion. Some laterite deposits are formed by wind erosion of the bedrock leaving a residuum of native gold metal at surface.

A bacterium, Cupriavidus metallidurans plays a vital role in the formation of gold nuggets, by precipitating metallic gold from a solution of gold (III) tetrachloride, a compound highly toxic to most other microorganisms.[1]

Platinum

Platinum and palladium are precious metals generally found in ultramafic rocks. The source of platinum and palladium deposits is ultramafic rocks which have enough sulfur to form asulfide mineral while the magma is still

liquid. This sulfide mineral (usually pentlandite, pyrite, chalcopyrite or pyrrhotite) gains platinum by mixing with the bulk of the magma because platinum is chalcophile and is concentrated in sulfides. Alternatively, platinum occurs in

association with chromite either within the chromite mineral itself or within sulfides associated with it.

Sulfide phases only form in ultramafic magmas when the magma reaches sulfur saturation. This is generally

thought to be nearly impossible by pure fractional crystallisation, so other processes are usually required in ore genesis models to explain sulfur saturation. These include contamination of the magma with crustal material,

especially sulfur-rich wall-rocks or sediments; magma mixing; volatile gain or loss.

Often platinum is associated with nickel, copper, chromium, and cobalt deposits.

Nickel

Main article: Kambalda type komatiitic nickel ore depositsMain article: Lateritic nickel ore deposits

Nickel deposits are generally found in two forms, either as sulfide or laterite.

Sulfide type nickel deposits are formed in essentially the same manner as platinum deposits. Nickel is a chalcophile

element which prefers sulfides, so an ultramafic or mafic rock which has a sulfide phase in the magma may form nickel sulfides. The best nickel deposits are formed where sulfide accumulates in the base of lava

tubes or volcanic flows — especiallykomatiite lavas.

Komatiitic nickel-copper sulfide deposits are considered to be formed by a mixture of sulfide segregation,

immiscibility, and thermal erosion of sulfidic sediments. The sediments are considered to be necessary to promote sulfur saturation.

Some subvolcanic sills in the Thompson Belt of Canada host nickel sulfide deposits formed by deposition of sulfides near the feeder vent. Sulfide was accumulated near the vent due to the loss of magma velocity at the vent

interface. The massive Voisey's Bay nickel deposit is considered to have formed via a similar process.

The process of forming nickel laterite deposits is essentially similar to the formation of gold laterite deposits, except

that ultramafic or mafic rocks are required. Generally nickel laterites require very large olivine-bearing ultramafic intrusions. Minerals formed in laterite nickel deposits include gibbsite.

Copper

Main article: Porphyry copperMain article: Manto ore deposits

Main article: Iron oxide copper gold ore deposits

Copper is found in association with many other metals and deposit styles. Commonly, copper is either formed within sedimentary rocks, or associated with igneous rocks.

The world's major copper deposits are formed within the granitic porphyry copper style. Copper is enriched by processes during crystallisation of the granite and forms as chalcopyrite — a sulfide mineral, which is carried up

with the granite.

Sometimes granites erupt to surface as volcanoes, and copper mineralisation forms during this phase when the

granite and volcanic rocks cool via hydrothermal circulation.

Sedimentary copper forms within ocean basins in sedimentary rocks. Generally this forms by brine from deeply

buried sediments discharging into the deep sea, and precipitating copper and often lead and zinc sulfides directly onto the sea floor. This is then buried by further sediment. This is a process similar to SEDEX zinc and lead,

although some carbonate-hosted examples exist.

Often copper is associated with gold, lead, zinc and nickel deposits.

Uranium

Main article: Uranium ore deposits

Citrobacter species can have concentrations of uranium in their bodies 300 times higher than in the surrounding environment.

Uranium deposits are usually sourced from radioactive granites, where certain minerals such as monazite are leached during hydrothermalactivity or during circulation of groundwater. The uranium is brought into solution by

acidic conditions and is deposited when this acidity is neutralised. Generally this occurs in certain carbon-bearing sediments, within an unconformity in sedimentary strata. The majority of the world's nuclear power is sourced from

uranium in such deposits.

Uranium is also found in nearly all coal at several parts per million, and in all granites. Radon is a common problem

during mining of uranium as it is a radioactive gas.

Uranium is also found associated with certain igenous rocks, such as granite and porphyry. The Olympic

Dam deposit in Australia is an example of this type of uranium deposit. It contains 70% of Australia's share of 40% of the known global low-cost recoverable uranium inventory.

Titanium and zirconium

Main article: Heavy mineral sands ore deposits

Mineral sands are the predominant type of titanium, zirconium and thorium deposit. They are formed by

accumulation of such heavy minerals within beach systems, and are a type ofplacer deposits. The minerals which contain titanium are ilmenite, rutile and leucoxene, zirconium is contained within zircon, and thorium is generally

contained within monazite. These minerals are sourced from primarily granite bedrock by erosion and transported

to the sea by rivers where they accumulate within beach sands. Rarely, but

importantly, gold, tin andplatinum deposits can form in beach placer deposits.

Tin, tungsten, and molybdenum

These three metals generally form in a certain type of granite, via a similar mechanism to intrusive-related gold and

copper. They are considered together because the process of forming these deposits is essentially the same. Skarn type mineralisation related to these granites is a very important type of tin, tungsten and molybdenum

deposit. Skarn deposits form by reaction of mineralised fluids from the granite reacting with wall rocks such as limestone. Skarn mineralisation is also important in lead, zinc, copper, gold and

occasionally uraniummineralisation.

Greisen granite is another related tin-molybdenum and topaz mineralisation style.

Rare earth elements, niobium, tantalum, lithium

The overwhelming majority of rare earth elements, tantalum and lithium are found within pegmatite. Ore genesis theories for these ores are wide and varied, but most involvemetamorphism and igneous activity. Lithium is present

as spodumene or lepidolite within pegmatite.

Carbonatite intrusions are an important source of these elements. Ore minerals are essentially part of the unusual

mineralogy of carbonatite.

Phosphate

Phosphate is used in fertilisers. Immense quantities of phosphate rock or phosphorite occur in sedimentary shelf

deposits, ranging in age from the Proterozoic to currently forming environments.[2] Phosphate deposits are thought to be sourced from the skeletons of dead sea creatures which accumulated on the seafloor. Similar to iron ore

deposits and oil, particular conditions in the ocean and environment are thought to have contributed to these deposits within the geological past.

Phosphate deposits are also formed from alkaline igneous rocks such as nepheline syenites, carbonatites and associated rock types. The phosphate is, in this case, contained within magmatic apatite, monazite or other rare-

earth phosphates.

SEDEX

Sedimentary exhalative deposits (abbreviated as SEDEX from SEDimentary EXhalative) are ore deposits which are interpreted to have been formed by release of ore-bearinghydrothermal fluids into a water reservoir (usually

the ocean), resulting in the precipitation of stratiform ore.

SEDEX deposits are the most important source of lead, zinc and barite, a major contributor

of silver, copper, gold, bismuth and tungsten.

Classification

The palaeoenvironmental setting and palaeogeologic setting of these ore deposits sets them apart from other lead, zinc or tungsten deposits which generally do not share the samesource or trap morphologies as SEDEX deposits.

SEDEX deposits are distinctive in that it can be shown that the ore minerals were deposited in a marine second-order basin environment, related to discharge of metal-bearing brines into the seawater. This is distinct from other

Pb-Zn-Ag and other deposits which are more intimately associated with intrusive or metamorphic processes or which are trapped within a rockmatrix and are not exhalative.

Genetic model

The process of ore genesis of SEDEX mineralisation is varied, depending on the type of ore which is deposited by

sedimentary exhalative processes.

• Source of metals is sedimentary strata which carry metal ions trapped

within clay and phyllosilicate minerals and electrochemically adsorbed to their surfaces. During diagenesis, the sedimenary pile dehydrates in response to heat and pressure, liberating a highly saline

formational brine, which carries the metal ions within the solution.

Alternately, SEDEX deposits may be sourced from magmatic fluids from subseafloor magma chambers and

hydrothermal fluids generated by the heat of a magma chamber intruding into saturated sediments. This scenario is relevant to mid-ocean ridge environments and island arc volcanic chains where black smokers are formed by

discharging hydrothermal fluids.

• Transport of these brines follows stratigraphic reservoir pathways toward faults, which isolate the buried

stratigraphy into recognisable sedimentary basins. The brines percolate up the basin bounding faults and are released into the overlying oceanic water.

• Trap sites are lower or depressed areas of the ocean topography where the heavy, hot brines flow and mix

with cooler sea water, causing the dissolved metal and sulfur in the brine to precipitate from solution as a

solid metal sulfide ore, deposited as layers of sulfide sediment.

Morphology

Upon mixing of the ore fluids with the seawater, dispersed across the seafloor, the ore constituents and gangue are

precipitated onto the seafloor to form an orebody and mineralization halo which are congruent with the underlying stratigraphy and are generally fine grained, finely laminated and can be recognized as chemically deposited from

solution.

Arkose-hosted SEDEX deposits are known in some cases, associated with arkosic strata adjacent to faults which

feed heavy brines into the porous sands, filling the matrix with sulfides, or deposited within a predominantly arkosic layer as a distinct chemical sediment layer usually associated with a shale interbed or at the lowermost levels of a

shale formation directly overlying arkosic sands (for example, copper deposits near Maun, Botswana).

Occasionally, mineralization is developed in faults and feeder conduits which fed the mineralizing system. For

instance, the Sullivan orebody in south-eastern British Columbia was developed within an interformational diatreme, caused by overpressuring of a lower sedimentary unit and eruption of the fluids through

another unit en route to the seafloor.

Within disturbed and tectonized sequences, SEDEX mineralization behaves similarly to other massive sulfide

deposits, being a low-competence low shear strength layer within more rigid silicate sedimentary rocks. As such, boudinage structures, dikes of sulfides, vein sulfides and hydrothermally remobilized and enriched portions or

peripheries of SEDEX deposits are individually known from amongst the various examples worldwide.

Mineralization types

SEDEX mineralization is best known in lead-zinc ore deposit classification schemes as the vast majority of the

largest and most important deposits of this type are formed by sedimentary-exhalative processes.

However, other forms of SEDEX mineralization are known;

• The supergiant deposits of the Zambian Copperbelt are considered to be SEDEX-style copper

mineralization formed at arkose-shale interfaces within sedimentary sequences. Within the Botswanan

extent of the Damaran Supergroup, the SEDEX nature is confirmed by chemical sediment limestones.

• The vast majority of the world's barite deposits are considered to have been formed by SEDEX

mineralization processes

• The scheelite (tungsten) deposits of the Erzgebirge in the Czech Republic are considered to be formed by

SEDEX processes

• Some gold associated with Carlin-type deposits of Nevada is interpreted to be stratiform chert or spillite

formed by SEDEX processes on the seafloor. This concept is controversial because most gold is clearly of later epigenetic origin.

Metal sources

The source of metals and mineralizing solutions for sedex deposits is deep formational brines in contact with sedimentary rocks.

Deep formational brines are defined as saline to hypersaline waters which are produced from sediments during diagenesis.

Metals such as lead and copper and zinc are found in a trace amount in all sediments. These metals are bound weakly to the hydrous clay minerals on the edges of the crystals and are held by weak bonds with hydroxyl groups.

Zinc is found within carbonate minerals bound within the carbonate crystal lattice at vertices and along crystal twin planes and crystal boundaries. These metals enter the sedimentary minerals due to adsorption from the seawater

which deposited them; few freshwater sediments are considered to have as much metal carrying capacity as saline waters.

Salt is also bound within the matrix of the sediments, generally in pore waters, trapped during deposition. In a typical mud on the seafloor up to 90% of the sediment volume and mass is represented by hydrogen and oxygen

either trapped in pore space as water or attached to phyllite minerals (clays) as hydroxyl bonds.

During diagenesis, pore water is squeezed out of the sediments and, as burial continues and heat increases, water

is liberated from clay minerals as the peripheral hydroxyl bonds are broken. As the rock enters the submetamorphic field, generally Zeolite facies metamorphism, clay minerals begin to recrystallize into low-temperature metamorphic

phyllite minerals such as chlorite, prehnite, pumpellyite, glauconite and so forth. This liberates not only water but incompatible elements attached to the mineral and trapped within crystal lattices.

Metals liberated from clay and carbonate minerals as they are changed from clays and low-pressure disordered carbonate forms enters the remaining pore fluid which by this time has become concentrated into what is known as

a deep formation brine. The solution of metal, salts and water produced by diagenesis is produced at temperatures between 150 - 350°C. Hydrothermal fluid compositions are estimated to have a salinity of up to 35% NaCl with

metal concentrations of 5-15 ppm Zn, Cu, Pb and up to 100ppm Ba and Fe. High metal concentrations are able to be carried in solution because of the high salinity. Generally these formational brines also carry considerable sulfur.

Deposition

The mineralizing fluids are conducted upwards within sedimentary units toward basin-bounding faults. The fluids move upwards due to thermal ascent and pressure of the underlying reservoir. Faults which host the hydrothermal

flow can show evidence of this flow due to development of massive sulfide veins, hydrothermal breccias, quartz and carbonate veining and pervasive ankerite-siderite-chlorite-sericite alteration.

Fluids eventually discharge onto the seafloor, forming areally extensive, stratiform deposits of chemical precipitates. Discharge zones can be breccia diatremes, or simple fumaroleconduits. Black smoker chimneys are

also common, as are seepage mounds of chert, jaspilite and sulfides.

Problems of classification

One of the major problems in classifying SEDEX deposits is in identifying whether or not the ore was definitively

exhaled into the ocean and whether the source was formational brines from sedimentary basins.

In the majority of cases the overprint of metamorphism and faulting, generally thrust faulting, deforms and disturbs

the sediments and obscured sedimentary features, although this is generally patchy so that the original configuration will be seen within the deposit.

Most deposits fit the model of having been formed late in the basin history and in most cases feeder systems and metal zonation support exhalative models. However, in the case ofdiatreme related deposits, such as the giant low-

grade Abra deposit, the mineralization is intra-formational, lacks sedimentary textures (is epigenetic and replacement type) and is too low in the basin profile (ie; in the basal formation).

Following the discovery of hydrothermal vents, deposits similar to those of oceanic vents and fossilized vent life forms have been found in some SEDEX deposits.[citation needed]

Specific examples of deposits

Sullivan Pb-Zn mine

The Sullivan Pb-Zn mine in British Columbia was worked for 105 years and produced 16,000,000 tonnes of lead and zinc, as well as 9,000 tonnes of silver. It was Canada's longest lived continuous mining operation and produced

metals worth over $20 billion in terms of 2005 metal prices. Grading was in excess of 5% Pb and 6% Zn.The ore genesis of the Sullivan ore body is summarized by the following process:

• Sediments were deposited in an extensional second-order sedimentary basin during extension

• Earlier, deeply buried sediments devolved fluids into a deep reservoir of sandy siltstones and sandstones

• Intrusion of dolerite sills into the sedimentary basin raised the geothermal gradient locally

• Raised temperatures prompted overpressuring of the lower sedimentary reservoir which breached

overlying sediments, forming a breccia diatreme• Mineralizing fluid flowed upwards through the concave feeder zone of the breccia diatreme, discharging

onto the seafloor

• Ore fluids debouched onto the seafloor and pooled in a second-order sub-basin's depocentre, precipitating

a stratiform massive sulfide layer from 3 to 8 m thick, with exhalative chert,manganese and barite.

References

• Karen D. Kelley, Robert R. Seal, II, Jeanine M. Schmidt, Donald B. Hoover, and Douglas P. Klein;

SEDIMENTARY EXHALATIVE ZN-PB-AG DEPOSITS; 1986, USGS

• Don MacIntyre, SEDIMENTARY EXHALATIVE Zn-Pb-Ag, British Columbia Geological Survey, 1992

Laterite

Laterites are soil types rich in iron and aluminium, formed in hot and wet tropical areas. Nearly all laterites are

rusty-red because of iron oxides. They develop by intensive and long-lasting weathering of the underlying parent rock. Tropical weathering (laterization) is a prolonged process of mechanical and chemical weathering which

produces a wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils. Laterites cover about one-third of the Earth's continental land area, with the majority of that in the land areas between the tropics

of Cancer and Capricorn.

Historically, laterite was cut into brick-like shapes and used in monument building. After 1000 CE construction

at Angkor Wat and other southeast Asian sites changed to rectangular temple enclosures made of laterite, brick and stone. Since the mid-1970s trial sections ofbituminous-surfaced low-volume roads have used laterite in place

of stone as a base course. Thick laterite layers are porous and slightly permeable, so the layers can function as aquifers in rural areas. Locally available laterites are used in an acid solution, followed by precipitation to

remove phosphorus and heavy metals at sewage treatment facilities.

Laterites are a source of aluminium ore; the ore exists largely in clay minerals and

the hydroxides, gibbsite, boehmite, and diaspore, which resembles the composition of bauxite. In Northern Ireland they once provided a major source of iron and aluminium ores. Laterite ores also were the early major source

of nickel.

Definition and physical description

Francis Buchanan-Hamilton first described and named a laterite formation in southern India in 1807.[1]:65 He named it laterite from the Latin word later, which means a brick; this rock can easily be cut into brick-shaped blocks

for building.[1]:65 The word laterite has been used for variably cemented, sesquioxide-rich soil horizons.[2] A sesquioxide is an oxide with three atoms of oxygen and two metal atoms. It has also been used for any reddish soil

at or near the Earth's surface.[2]

Laterite is a surface formation rich in iron and aluminium, formed in hot and wet tropical areas. It develops by

intensive and long-lasting weathering of the underlying parent rock. Nearly all laterites are rusty-red because of iron oxides. Laterite covers are thick on the stable areas of the African Shield, the South American Shield and

the Australian Shield.[3]:1 In Madhya Pradesh, India, the laterite which caps the plateau is 30 m (100 ft) thick.[4]:554 Laterites can be either soft and easily broken into smaller pieces, or firm and physically

resistant.Basement rocks are buried under the thick weathered layer and rarely exposed.[3]:1 Lateritic soils form the uppermost part of the laterite cover.

Formation

Laterite is often located under residual soils.

A represents soil; B represents laterite, a regolith; C represents saprolite, a less-weathered regolith; D represents bedrock

Tropical weathering (laterization) is a prolonged process of mechanical and chemical weathering which produces a

wide variety in the thickness, grade, chemistry and ore mineralogy of the resulting soils.[5]:3 A period of active laterization extended from about the mid-Tertiary to the mid-Quaternary periods (35 to 1.5 million years ago).

[5]:3 Statistical analyses show that the transition in the mean and variance levels of18O during the middle of the Pleistocene was abrupt.[6] It seems this abrupt change was global and mainly represents an increase in ice mass;

at about the same time an abrupt decrease in sea surface temperatures occurred; these two changes indicate a sudden global cooling.[6] The rate of laterization would have decreased with the abrupt cooling of the earth.

Weathering in tropical climates continues to this day, at a reduced rate.[5]:3

Laterites are formed from the leaching of parent sedimentary rocks (sandstones, clays, limestones); metamorphic

rocks (schists, gneisses,migmatites); volcanic rocks (granites, basalts, gabbros, peridotites); and mineralized proto-ores;[3]:5 which leaves the more insoluble ions, predominantly iron and aluminium. The mechanism of leaching

involves acid dissolving the host mineral lattice, followed by hydrolysis and precipitation of insoluble oxides and sulfates of iron, aluminium and silica under the high temperature conditions[7] of a humid sub-

tropicalmonsoon climate.[8] An essential feature for the formation of laterite is the repetition of wet and dry seasons.[9] Rocks are leached by percolating rain water during the wet season; the resulting solution containing

the leached ions is brought to the surface by capillary actionduring the dry season.[9] These ions form soluble salt compounds which dry on the surface; these salts are washed away during the next wet season.[9] Laterite

formation is favoured in low topographical reliefs of gentle crests and plateaus which prevents erosion of the surface cover.[5]:4 The reaction zone where rocks are in contact with water – from the lowest to highest water

table levels – is progressively depleted of the easily leached ions of sodium, potassium, calcium and magnesium.[9] A solution of these ions can have the correct pH to preferentially dissolve silicon oxide rather than the aluminium

oxides and iron oxides.[9]

The mineralogical and chemical compositions of laterites are dependant on their parent rocks.[3]:6 Laterites consist

mainly of quartz and oxides of titanium, zircon, iron, tin, aluminium and manganese, which remain during the course of weathering.[3]:7 Quartz is the most abundant relic mineral from the parent rock.[3]:7 Laterites vary

significantly according to their location, climate and depth.[7] The main host minerals for nickel and cobalt can be either iron oxides, clay minerals or manganese oxides.[7] Iron oxides are derived from mafic igneous rocks and

other iron-rich rocks; bauxites are derived from granitic igneous rock and other iron-poor rocks.[9] Nickel laterites occur in zones of the earth which experienced prolonged tropical weathering of ultramafic rocks containing the

ferro-magnesian minerals olivine, pyroxene, and amphibole.[5]:3

Locations

Yves Tardy, from the French Institut National Polytechnique de Toulouse and the Centre National de la Recherche

Scientifique, calculated that laterites cover about one-third of the Earth's continental land area.[3]:1 Lateritic soils are the subsoils of the equatorial forests, of the savannasof the humid tropical regions, and of

the Sahelian steppes.[3]:1 They cover most of the land area between the tropics of Cancer and Capricorn; areas not covered within these latitudes include the extreme western portion of South America, the southwestern portion

of Africa, the desert regions of north-central Africa, the Arabian peninsula and the interior of Australia.[3]:2

Some of the oldest and most highly deformed ultramafic rocks which underwent laterization are found in the

complex Precambrian shields in Brazil and Australia.[5]:3 Smaller highly deformed Alpine-type intrusives have formed laterite profiles in Guatemala, Columbia, Central Europe, India and Burma.[5]:3 Large thrust sheets

of Mesozoic to Tertiary 251- to 65-million-year-old island arcs and continental collision zones underwent laterization in New Caledonia, Cuba, Indonesia and the Philippines.[5]:3 Laterites reflect past weathering conditions;[2]laterites

which are found in present-day non-tropical areas are products of former geological epochs, when that area was near the equator. Present-day laterite occurring outside the humid tropics are considered to be indicators of climatic

change, continental drift or a combination of both.[10]

Uses

Building blocks

Cutting laterite bricks in Angadipuram, India

When moist, laterites can be easily cut with a spade into regular-sized blocks.[3]:1 Laterite is mined while it is below the water table, so it is wet and soft.[11] Upon exposure to air it gradually hardens as the moisture between the flat clay particles evaporates and the larger iron salts[9]lock into a rigid lattice structure [11] :158 and become

resistant to atmospheric conditions.[3]:1 The art of quarrying laterite material into masonryis suspected to have

been introduced from the Indian subcontinent.[12]

After 1000 CE Angkorian construction changed from circular or irregular earthen walls to rectangular temple

enclosures of laterite, brick and stone structures.[13]:3 Geographic surveys show areas which have laterite stone alignments which may be foundations of temple sites that have not survived.[13]:4 The Khmer people constructed

the Angkor monuments – which are widely distributed in Cambodia and Thailand – between the 9th and 13th centuries.[14]:209 The stone materials used were sandstone and laterite; brick had been used in monuments

constructed in the 9th and 10th centuries.[14]:210 Two types of laterite can be identified; both types consist of the minerals kaolinite, quartz, hematite and goethite.[14]:211 Differences in the amounts of minor elements arsenic,

antimony, vanadium and strontium were measured between the two laterites.[14]:211

Angkor Wat – located in present-day Cambodia – is the largest religious structure build by Suryavarman II, who

ruled the Khmer Empire from 1112 to 1152.[15]:39 It is a World Heritage site.[15]:39 The sandstone used for the building of Angkor Wat is Mesozoic sandstone quarried in the Phnom Kulen Mountains, about 40 km (25 mi) away

from the temple.[16] The foundations and internal parts of the temple contain laterite blocks behind the sandstone surface.[16] The masonry was laid without joint mortar.[16]

Road building

Laterite road near Kounkane, Upper Casamance, Senegal

The French surfaced roads in the Cambodia, Thailand and Viet Nam area with crushed laterite, stone or gravel.[17] Kenya, during the mid-1970s, and Malawi, during the mid-1980s, constructed trial sections of bituminous-

surfaced low-volume roads using laterite in place of stone as a base course.[18] The laterite did not conform with any accepted specifications but performed equally well when compared with adjoining sections of road using stone

or other stabilized material as a base.[18] In 1984 US$40,000 per 1 km (0.62 mi) was saved in Malawi by using laterite in this way.[18]

Water supply

Bedrock in tropical zones is often granite, gneiss, schist or sandstone; the thick laterite layer is porous and slightly permeable so the layer can function as an aquifer in rural areas.[3]:2 One example is the Southwestern Laterite

(Cabook) Aquifer in Sri Lanka.[19]:1 This aquifer is on the southwest border of Sri Lanka, with the narrow Shallow Aquifers on Coastal Sands between it and the ocean.[19]:4 It has considerable water-holding capacity, depending

on the depth of the formation.[19]:1 The aquifer in this laterite recharges rapidly with the rains of April–May which follow the dry season of February–March, and continues to fill with the monsoon rains.[19]:10 The water table

recedes slowly and is recharged several times during the rest of the year.[19]:13 In some high-density suburban areas the water table could recede to 15 m (50 ft) below ground level during a prolonged dry period of more than 65

days.[19]:13 The Cabook Aquifer laterites support relatively shallow aquifers that are accessible to dug wells.[19]:10

Waste water treatment

In Northern Ireland phosphorus enrichment of lakes due to agriculture is a significant problem.[20] Locally available laterite – a low-grade bauxite rich in iron and aluminium – is used in acid solution, followed by precipitation to

remove phosphorus and heavy metals at several sewage treatment facilities.[20] Calcium-, iron- and aluminium-rich solid media are recommended for phosphorus removal.[20] A study, using both laboratory tests and pilot-scale

constructed wetlands, reports the effectiveness of granular laterite in removing phosphorus and heavy metals from landfill leachate.[20] Initial laboratory studies show that laterite is capable of 99% removal of phosphorus from

solution.[20] A pilot-scale experimental facility containing laterite achieved 96% removal of phosphorus.[20] This removal is greater than reported in other systems.[20] Initial removals of aluminium and iron by pilot-scale facilities

have been up to 85% and 98% respectively.[20] Percolating columns of laterite removed enough cadmium, chromium and lead to undetectable concentrations.[20] There is a possible application of this

low-cost, low-technology, visually unobtrusive, efficient system for rural areas with dispersed point sources of pollution.[20]

Ores

Ores are concentrated in metalliferous laterites; aluminium is found in bauxites, iron and manganese are found in

iron-rich hard crusts, nickel and copper are found in disintegrated rocks, and gold is found in mottled clays.[3]:2

Bauxite

Bauxite on white kaolinitic sandstone at Pera Head, Weipa, Australia

Bauxite ore is the main source for aluminium.[1]:65 Bauxite is a sedimentary rock, so it has no precise chemical formula.[21] It is composed mainly of hydrated alumina minerals such as gibbsite [Al(OH)3 or Al2O3 . 3H2O)] in

newer tropical deposits; in older subtropical, temperate deposits the major minerals are boehmite [ -AlO(OH) orγ Al2O3.H20] and some diaspore [ -AlO(OH) or Al2O3.H20].α [21] The average chemical composition of bauxite, by

weight, is 45 to 60% Al2O3 and 20 to 30% Fe2O3.[21] The remaining weight consists of silicas (quartz, chalcedonyand kaolinite), carbonates (calcite, magnesite and dolomite), titanium dioxide and water.

[21] Formation of lateritic bauxites occurs world-wide in the 145- to 2-million-year-old Cretaceous and Tertiary coastal plains.[22] The bauxites form elongate belts, sometimes hundreds of kilometers long, parallel to Lower

Tertiary shorelines in India and South America; their distribution is not related to a particular mineralogical composition of the parent rock.[22] Many high-level bauxites are formed in coastal plains which were subsequently

uplifted to their present altitude.[22]

Iron

The dark veins are precipitated iron within kaolinized basalt near Hungen, Vogelsbery, Germany.

The basaltic laterites of Northern Ireland were formed by extensive chemical weathering of basalts during a period

of volcanic activity.[8] They reach a maximum thickness of 30 m (100 ft) and once provided a major source of iron and aluminium ore.[8] Percolating waters caused degradation of the parent basalt and preferential precipitation by

acidic water through the lattice left the iron and aluminium ores.[8] Primaryolivine, plagioclase feldspar and augite were successively broken down and replaced by a mineral

assemblage consisting of hematite, gibbsite,goethite, anatase, halloysite and kaolinite.[8]

Nickel

Irregular weathering of grey serpentiniteto greyish-brown nickel-containing literite with a high iron percentage (nickel limonite), near

Mayaguex, Puerto Rico.

Laterite ores were the major source of early nickel.[5]:1 Rich laterite deposits in New Caledonia were mined starting the end of the 19th century to produce white metal.[5]:1 The discovery of sulfide deposits of Sudbury, Ontario,

Canada, during the early part of the 20th century shifted the focus to sulfides for nickel extraction.[5]:1 About 70% of the Earth's land-based nickel resources are contained in laterites; they currently account for about 40% of the

world nickel production.[5]:1 In 1950 laterite-source nickel was less than 10% of total production, in 2003 it accounted for 42%, and by 2012 the share of laterite-source nickel is expected to be 51%.[5]:1 The four main areas

in the world with the largest nickel laterite resources are New Caledonia, with 21%; Australia, with 20%; the Philippines, with 17%; and Indonesia, with 12%.[5]:4

A represents soil; B represents laterite, a regolith; C represents saprolite, a less-weathered regolith; beneath C is bedrock

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Geographies of India. Cambridge University Press. Retrieved april 6, 2010.

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Implications for Laterite Definition, Genesis, and Age". Geographical Review (American Geographical

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3. Tardy, Yves (1997). Petrology of Laterites and Tropical Soils. ISBN 90-5410-678-6. Retrieved April 17, 2010.

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Interbasaltic Formation, Northern Ireland". Chemical Geology 166: 65. doi:10.1016/S0009-2541(99)00179-5.

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10.^ Bourman, R.P. (August 1993). "Perennial problems in the study of laterite: A review". Australian Journal of Earth

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15.(2006) A Preliminary Study on the Direction Dependence of Sandstone Column Deterioration in the First Gallery of

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17.^ Sari, Betti Rosita (2004). "The Trade Route in the Cambodian/Thai Border Areas: Challenges and

Opportunities". Journal of Masyarakat Indonesia: 6. Retrieved April 17, 2010.

18.Grace, Henry (September 1991). "Investigations in Kenya and Malawi using as-dug laterite as bases for bituminous

surfaced roads". Journal Geotechnical and Geological Engineering (Springer Netherlands) 9:

183. doi:10.1007/BF00881740. Retrieved April 17, 2010.

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