non-metallic mineral deposits

Nonmetallic Mineral Deposits (GE3115)

Prof. Dr. H.Z. Harraz Presentation - Nonmetallic Deposits

A short series of lectures prepared for the

Third year of Special Geology, Tanta University

(GE3115)

2014- 2015

by

Hassan Z. Harraz

[email protected]

To Final Product

From raw material

Outline of Topic :

6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 3

We will explore all of the above in Topic.

Earth Resources Reserves and resources Nonrenewable Mineral Resources What are industrial minerals? Why are industrial minerals so important? Geology of Industrial Minerals Deposits Classification of industrial minerals General characteristics of Non-metallic Deposits Factors important in evaluating an industrial minerals deposit Selected industrial rocks and minerals

1) ABRASIVES MINERALS

2) OLIVINE

3) CLAY MINERALS

4) FLUORITE

5) PERLITE

6) BUILDING STONES and Rip-rap

7) SULFUR ORE DEPOSITS

8) CALCIUM CARBONATE DEPOSITS

9) CHERT DEPOSITS

10) PHOSPHATE ORE DEPOSITS

11) EVAPORITE DEPOSITS

12) GYPSUM

13) SELECTED SOME NON-METALLIC METAMORPHIC DEPOSITS

13.1) Asbestos Deposits

13.2) Graphite Deposits

13.3) Talc, Soapstone, and Pyrophyllite

13.4) Selected Some Ornamental Metamorphic Stones

13.4.1) Marble 13.4.2) Quartzite 13.4.3) Serpentinite

What is a mineral?

Mineral: inorganic compound that occurs naturally in the earth’s crust

Solid

Regular internal crystalline structure

Definite chemical composition.

Rock is solid combination of one or more minerals.

What are orebody?

are aggregates of different minerals

have high concentrations of metal bearing minerals and

are hosted in barren “country” rock {Mined country rock is referred to as gangue (or

waste)}.

What is an Ore Deposit?

Ore deposit is an occurrence of minerals or metals in sufficiently high concentration to

be profitable to mine and process using current technology and under current economic conditions.

Ore deposits may be considered as:

Commercial mineral deposits (i.e., Ore: suitable for mining in the present

times) or

Non-commercial ore deposits (i.e., Protore: problems in mining, transportation,

prices....etc).

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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 4

What is an Ore? Ore: Rock materials that exist in quantities that can be extracted and profitably mined

for a mineral (often a metal) or for minerals (metals).

An ore is a mass of mineralization within the Earth's surface which can be mined:

at a particular place;

at a particular time;

at a profit

Marketed for a profit.

Ore: refers to useful metallic minerals that can be mined at a profit and, in

common usage, to some non-metallic minerals such as fluorite and sulfur.

To be considered of value, an element must be concentrated above the level of

its average crustal abundance:

High Grade Ore; has high concentration of the mineral

Low Grade Ore: smaller concentration

Most non-metallic minerals are generally not called ores, but

rather they are called Industrial Minerals

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What is gangue (or waste)? Gangue (or Waste): Minerals other than ore present in a rock.

Gangue (or Waste) is mineralized rock that is removed from a mine to provide

access to an underlying or nearby orebody containing at least one mineral of

value.

Types of Gangue (or Waste):

Typically pure barren materials;

Gangue material contained within the ore

Gangue (or Waste) rock can become ore at some later point in time.

Non-Metallic / commodity prices can change

Other values are discovered within the waste

New technology is developed

Cost of environmental protection becomes too high

Non-metallic minerals has been exhausted; too costly to close the mine.

Political factors

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Finding a Deposit


The old fashioned way

of finding a mine was

your prospector with a

pick and shovel, a gold

pan, and a lot of luck.

Today, technologies used

include, but are not limited to,

exploration geology, geophysics, geochemistry, and satellite imagery.

Finding a Deposit


Geophysics

Geophysical exploration involves searching for favorable mineral deposits using the physical properties of rocks.

Geophysical investigations ground-penetrating radar studies or the use of seismic waves to show contrasting rock types.

The selected rock units of interest might then be mapped and sampled.

Geochemistry

Geochemists can determine the composition of what

lies below the Earth's surface by sampling soil. Soil at

the surface can carry a chemical signature of what lies

below, because of the movement of chemicals through

the rise and fall of the water table.

Positive geochemical results from surface sampling are

followed by a drilling program. Because of the great

expense, drilling is only carried out when the area is very

likely to contain substantial mineral deposits.

Drilling produces either rock fragments, or 'cores' of rock

for sampling to determine whether the mineral deposit

contains worthwhile concentrations of ore mineral

Geology

Geology is the study of the planet

Earth—the materials of which our planet

is made, the processes that act on these

materials, and the products formed.

Geologists use ground-mapping

techniques to identify features seen on

satellite images and aerial maps of large

tracts of the continent.

Remote sensing: Landsat and Satellite

Imagery

Ground-based surveys are expensive,

and one can often experience difficulty

in mapping large-scale structures.

However, large geological structures are

often readily visible on satellite imagery.

Reserves vs. Resources Reserves

Natural resources that

have been discovered &

can be exploited profitably

with existing technology.

Resources

The term ―resource‖ refers to the

total amounts of a commodity of

particular economic use that is

present in an area. These

estimates include both extractable

and non-extractable amounts of

this commodity.

Deposits that we know or believe to

exist, but that are not exploitable

today because of technological,

economical, or political reasons

Earth Resources may be

Renewable and/or Non-renewable

resources


Compared between Renewable and Non-renewable Mineral Resources

Renewable resources Non-renewable resources

Resource can be replenished over

relatively short time spans

Significant deposits take

millions of years to form; from

a human perspective there

are fixed quantities

Renewable can be:- It’s a one-time only deal. i) Perpetual Renewable

Resources

ii) Potentially Exhaustible/

Renewable Resources Once exploited and used the

resource is gone forever. Direct solar energy.

Energy from flowing water, sun, wind

Indirect effects related to

hydrological cycle (e.g., wind,

oceans, tides, running water

…etc).

Alternate/futuristic energy

resources:

Geothermal energy

Solar energy

• Fresh Air

• Fresh Water

• Fertile Soil

• Biodiversity: Examples include : Plants

Animals for food

Trees for lumber

Examples:

Fuels (coal, oil, natural

gas)

Metals (iron, copper,

uranium, gold)


Mineral Resources Non-metallic mineral deposits (NM)

Industrial Minerals (IM)): Sulfur, Gypsum, Coal, Barite, Salt, Clay, Feldspar, Borax, Lime, Magnesite, Potash, Phosphates, Silica, Fluorite, Asbestos, Abrasives, Mica.

Precious stones: Gem Minerals,

Construction minerals : Stone, Sand, Gravel, Limestone

Metallic mineral deposits or (Ore mineral deposits):

Ferrous metals: Iron and Steel, Cobalt, Nickel

Non-ferrous (or base metals): Copper, Zinc, Tin, Lead, Aluminum,

Titanium, Manganese, Magnesium, Mercury, Vanadium, Molybdenum,

Tungsten.

Precious metals: Silver, Gold, Platinum

Energy Resources(or Energy minerals):

Fossil Fuels: Coal, Oil, Natural Gas

Radioactive Minerals: Uranium

Geothermal Energy


Non-metals

Metals

Year

0

4

8

12

Billi

on

Can

$

16

1985

1990

1995

2000

Industrial Minerals and Metal Production

in Canada

50%

75%

(Industrial Minerals and

Structural Materials) ★

B.C.


Fig.2: Selected raw materials consumed in the U.S., 1900-95. For this graph, construction materials (crushed stone, sand and gravel) have been separated from the remainder of the industrial minerals to illustrate the upsurge in construction following the end of World War II

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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 14 http://eps.berkeley.edu/courses/eps50/documents/lecture31.mineralresources.pdf

14

Coal, gas, oil, uranium

Iron ore, niobium, tantalum

Gold, Silver,

platinum

Diamond, gems

Brick, building stone, cement, clay, crushed

rock aggregate, gypsum, sand,

slate, gravel

Bentonite, industrial

carbonates, kaolin, magnesia, potash, salt, sand,

silica, sulphur

Bauxite/aluminium, cobalt, copper, lead, zinc, nickel,

molybdenum

Jewellery, monetary, industrial

Construction Jewellery, industrial

Ceramics, chemical, foundry casting, fillers/pigments,

fuel, gas, iron, steel, metallurgy, water

treatment

Construction, electrical/electronic

, engineering, manufacturing

Aerospace, contruction, electronic,

engineering, manufacturing, steel making

Electricity, organic chemical/plastics,

process fuel, transportation

Energy minerals Non-metallic minerals Metallic minerals

Minerals

Precious metals

Ferrous metals

Base metals

Construction minerals

Industrial minerals

Precious stones

End Use

Mineral Resources

Non-metallic Resources • Non-metallic resources - not mined to

extract a metal or an energy source. Construction Materials

• sand, gravel, limestone, and gypsum

Agriculture

• phosphate, nitrate and potassium

compounds.

Industrial uses

• rock salt, sulfur

Gemstones

• diamonds, rubies, etc.

Household and Business Products

• glass sand, diatomite

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Non-metallic Mineral Resources


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Typical examples of natural Industrial Mineral Deposits : Clays

Silica sand

Talc

Limestone/chalk

Gypsum

Pumice

Potash

Carbonate Minerals

Evaporite Salts

Phosphate

Sulphur

made from: Mullite bauxite, kaolin

Aluminas bauxite

Silicon carbide quartz + coke

ppt calcium

carbonate lime & CO2

Spinel magnesite + alumina

Soda salt + limestone + coal +

ammonia

Fused minerals alumina, magnesia, spinel

Typical examples of synthetic IM:

What are Non-metallic Deposits?

Steps in Obtaining Mineral Commodities 1) Prospecting: finding places where non-metallic minerals occur.

2) Mine exploration and development: learn whether non-metallic

minerals can be extracted economically.

3) Mining: extract non-metallic minerals from ground.

4) Beneficiation: separate non-metallic minerals from other mined

rock. (Mill)

5) Refining: extract pure mineral commodity from the ore mineral

(get the good stuff out of waste rock) (Refinery)

6) Transportation: carry commodity to market.

7) Marketing and Sales: Find buyers and sell the commodity.

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Geology of Industrial Minerals Deposits

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Geology provides the framework in which mineral exploration and the integrated procedures of remote sensing, geophysics, and geochemistry are planned and interpreted.

Non-metallic mineral deposits life cycle

Supply Sector

exploration

mineral finance

plant engineering

mining

processing

Logistics Sector

trading

port handling

mineral inspection

freight

warehousing/distribution

Consuming Market

Sector

direct market mineral consumer

intermediate market mineral consumer

end market mineral consumer

SUPPLY

DEMAND


Mine to market supply chain

Supply sector

Logistics sector

Consuming market sector

• centres of high population

• their economy - the driver

• directly influence demand for NM

Why are Non-Metallic Deposits so important?

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Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 23 23

Nonmetallic Deposits in your kitchen

6 November

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IM in

your

kitchen

Glass/glasses/ light bulbs silica sand, limestone, soda ash, borates,

feldspar, lithium

Ceramic tiles/mugs/ plates

….etc.

kaolin, feldspar, talc, wollastonite, borates,

alumina, zirconia

Paint TiO2, kaolin, mica, talc, wollastonite, GCC, silica

Plastic white goods

eg. fridge, washer

talc, GCC, kaolin, mica, wollastonite, flame

retardants (ATH, Mg(OH)2)

Wooden flooring treatment materials- borates, chromite

Drinking water treatment materials- lime, zeolites

Wine/beer diatomite, perlite filters

Salt salt

Sugar lime in processing

Detergents/soap borates, soda ash, phosphates

Surfaces marble, granite

Books kaolin, talc, GCC, lime, TiO2 in paper

Oven glass petalite, borates

Heating elements fused magnesia insulators

Wallboard/plaster gypsum, flame retardants

Metal pots/cutlery mineral fluxes & refractories in smelting

Why are NM so important?

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Main consuming market mineral sectors

Abrasives Foundry

Absorbents Glass

Agricultural Metallurgy

Cement Paint

Ceramics Pigments

Chemicals Paper

Construction Plastics

Oil well drilling Refractories

Electronics Flame retardants

Filtration Welding

General characteristics of Non-metallic Deposits


Highest volume and tonnage

low value, but vital commodities

High total value

Prices are more stable

NM are prerequisite raw materials for a wide range of industrial and domestic products

Recycling is not much of an issue

Price of the unit value is so low that transportation becomes a major issue

Rarely exported.

Feasibility study: Often need to find a market before looking for a nearby deposit

Depending on their uses, product purity and grain size may become very important factors in deciding the suitability and price of the commodity

NM support and add value to industrial sectors

Market demand drives NM supply

Classification of Non-metallic Deposits


End-use and genesis (Bates, 1960)

By unit price and bulk (Burnett, 1962)

Unit value, place value, representative value (Fisher,

1969)

Chemical and physical properties (Kline, 1970)

Geologic occurrence and end-use (Dunn, 1973)

Geology of origin (Harben and Bates, 1984)

Alphabetical (Harben and Bates, 1990; Carr, 1994)

Classification of Non-metallic deposits (Cont.) Rock classification Mineral classification

A) Igneous Rocks

Granite

Basalt and diabase

Pumice and pumicite

Perlite

B) Metamorphic Rocks

Slate

Marble

Serpentinite

Schist

Gneiss

C) Sedimentary Rocks

Sand and gravel

Sandstone

Clay

Limestone and dolomite

Phosphate rock

Gypsum

Salt

A) Igneous Minerals

Nepheline syenite

Feldspar

Mica

Lithium minerals

Beryl

B) Vein and Replacement Minerals

Quartz crystal

Fluorspar

Barite

Magnesite

C) Metamorphic Minerals

Graphite

Asbestos

Talc

Vermiculite

Emerald

D) Sedimentary Minerals and sulfur

Diatomite

Potash minerals

Sodium minerals

Borate

Nitrates

Sulfur

Factors important in evaluating a Non-metallic deposits


Customer specifications

Distance to customer (transportation)

Ore grade--concentration of the commodity in the deposit

By-products

Commodity prices

Mineralogical form

Grain size and shape

Undesirable substances

Size and shape of deposit

Ore character

Cost of capital

Location

Environmental consequences/ reclamation/bonding

Land status

Taxation

Political factors


1) Abrasives Minerals:

Abrasive mineral is a material, often a mineral, that is used to shape or finish a work-piece through rubbing which leads to part of the work-piece being worn away

Abrasives may be classified as either natural or synthetic.:

Selected Nonmetallic Deposits:

Naturally Abrasives Synthetic Abrasives

Coarse Abrasives Scrubbing Powders Soft Abrasives

Emery (impure corundum) Diatomite Ground Feldspar Silicon carbide

(carborundum)

Pumice Chalk Tungsten Carbide

Corundum Kaolin Boron carbide

Sandstone Ceramic iron oxide

Sand Corundum

Tripoli

Rouge

Garnet

Feldspar Steel abrasive

Calcite Zirconia alumina

Slags Quartz

Diamonds


The mineral olivine (when of gem quality, it is also called peridote) is a magnesium iron silicate with the formula (Mg+2, Fe+2)2SiO4.

Extracted from large dunite bodies.

Uses:

Slag conditioner in iron and steel making; refractory bricks.

Blast cleaning agent: Olivine is also used to tap blast furnaces in the steel industry, acting as a plug, removed in each steel run.

Foundry sand: The aluminium foundry industry uses olivine sand to cast objects in aluminium.

2) Olivine:

Clay Grades are categorized into six groups: 1) Kaolin or China clay: white, claylike material composed mainly of

kaolinite industrial applications: paper coating and filling, refractories, fiberglass and insulation, rubber, paint, ceramics, and chemicals

2) Ball clay: kaolin with small amount of impurities industrial application: dinnerware, floor tile, pottery, sanitary ware.

3) Fire clays: kaolin with substantial impurities (diaspore, flint) industrial applications: refractories

4) Bentonite (smectite): clay composed of smectite minerals, usually montmorillonite industrial applications: Oil well drilling fluids,

suspending agents; drilling muds, foundry sands 5) Fuller’s earth: nonplastic clay high in magnesia, a similar to bentonite

industrial applications: absorbents 6) Shale: laminated sedimentary rock consisting mainly of clay minerals

mud industrial application: raw material in cement and brick manufacturing

3) Clay minerals:

4) Fluorite (or Fluorspar): Fluorite is the mineral form of calcium fluoride, (CaF2). In the mining industry fluorite is often called "fluorspar."

Fluorite is deposited in veins by hydrothermal processes. In these rocks it often occurs as a gangue mineral associated with metallic ores.

Fluorite is also found in the fractures and cavities of some limestones and dolomites.

It is used in a wide variety of chemical, metallurgical and ceramic processes, however, optical, lapidary and other uses are also important. Acid grade (97% CaF2): The purest grades of fluorite are a source of fluoride for

hydrofluoric acid (HF) manufacture, which is the intermediate source of most fluorine-containing fine chemicals.

Ceramic grade (80 – 96% CaF2): used for the manufacture of ceramics, enamels, glasses and glass fibers.

Metallurgical grade (> 60% CaF2): used in the iron and steel industry.

Optical Grade Fluorite: Specimens of fluorite with exceptional optical clarity have been used as lenses. Fluorite has a very low refractive index and a very low dispersion. These two characteristics enable the lens to produce extremely sharp images. These lenses are used in optical equipment such as microscopes, telescopes and cameras

Lapidary Grade Fluorite:


5) Perlite:

Perlite is a water bearing natural glass

That contains Silica, Alumina, Iron, Titanium,

Calcium, Magnesium, Sodium and potassium

Oxides

http://z.about.com/d/geology/1/0/5/S/1/rocpicperlite.jpg

5) Perlite: Perlite is an amorphous volcanic glass that has a relatively high water

content (i.e., typically formed of the hydration of obsidian).

It occurs naturally and has the unusual property of greatly expanding when

heated sufficiently.

It is an industrial mineral and a commercial product useful for its light

weight after processing.

Various grades resulting from differences in the degree of hydration.

Used primarily as an insulator with its high heat resistance and high sound absorption.

Used in fertilizer


6) Building Stones


Durability and hardness

Ease of quarrying

Color and aesthetic value

Impurities and other undesirables

These come from all geological environments.

The most important economic factor for building materials is that the material has to be close to where it is going to be used, as the highest cost is in its transportation.

Building stones are by far the lowest cost geological materials and their value is usually in the order of only a few dollars per ton

Building Stones may be:

i) Crushed rock (or Aggregate Stone): Natural aggregate (crushed stone, sand, and gravel) is the most commonly used building material, along with concrete which is derived from crushed limestone. Bricks are made from fine aggregate along with clay which acts as the binding material, and iron oxide minerals for colouration.

Aggregate is also used as a sub-surface lining on our roads.

Plaster is derived from crushed and refined gypsum.

Coarse and fine aggregates

Fillers

Proximity to market

Optimum targets for exploitation. ii) Dimension (or Ornamental) stones are much higher-value building material and are used as decorative

facings on buildings. Examples: Marble, Quartzite, Gneiss, Schist, Serpentinite, Slate, Migmatite. By far the most commonly used dimension stones are marbles.

Characteristics of Building stones

Rip-rap There are many techniques used for reducing the power of

waves before they erode a coastline.

• Rip-rap is a sheet of boulders used at the toe of a slope to add weight and break the force of the waves.

• Rip-rap is made of highly resistant rocks to physical and

chemical weathering, often Basalt, Gabbro, Dolerite, Quartzite, Granite, or Gneiss, which will not weather or

break down.

• Because the blocks are angular, they fit together tightly, but still allow water to drain through back to the sea.


The part of the coast was in the process of being reinforced with a wall of rip-rap. Beyond the wall was a grassy area with geotextiles and plants to reduce further the force of the waves.

RIP-RAP

Area of soft rocks which needed to be reinforced.

St Bees Head, Lake District

Geotextiles help to support the glacial till slope so that vegetation can establish itself.

Slope angle has been reduced

Rip-rap

Till cliffs

Rip-rap

Quartzite is highly resistant to physical and chemical weathering, so it does well in applications like this rip-rap

Introduction Sulfur (S) composes 0.06% of Earth’s crust

Sulfur (S) is an important constituent of volcanic gases, magmatic emanations, and is common in hot springs.

Elemental Sulfur is found on the Earth in:

Volcanic deposits or volcanic emanations (i.e., Fumaroles)

Underground deposits

On Earth, elemental sulfur can be found near hot springs and volcanic regions in many

parts of the world, especially along the Pacific Ring of Fire; such volcanic deposits are

currently mined in Indonesia, Chile, and Japan.

Sulfur is deposited from sulfates (SO4) and hydrogen sulfide (H2S) in bodies of water

where reducing conditions.

Sulfates (SO4) are also reduced by anaerobic bacterial (e.g., Clostridium nigrificans) to

hydrogen sulfide (H2S), which, in turn oxidises to sulfur (S) and water (H2O).

7) Sulfur Ore Deposits


Sulfur Reservoirs in Nature Sulfur (S) is distributed in the earth's crust in

the form of sulfates (SO4), sulfides, and native sulfur.

The largest physical reservoir is the Earth's crust where sulfur is found in gypsum (CaSO4.2H2O) and pyrite (FeS2).

The largest reservoir of biologically useful sulfur is found in the ocean as sulfate anions (2.6 g/L), dissolved hydrogen sulfide (H2S) gas, and elemental sulfur.

• Elemental sulfur was once extracted from salt domes where it sometimes occurs in nearly pure form, but this method has been obsolete since the late 20th century.

• Today, almost all elemental sulfur is produced as a by-product of removing sulfur-containing contaminants from natural gas and petroleum.

Sulfur also obtained from by-products of several industrial processes (H2S(g) from oil and natural gas deposits)

Sulfur powder

Roll Sulfur


http://en.wikipedia.org/wiki/Natural_gas

http://en.wikipedia.org/wiki/Petroleum

• Subsurface sulfur recovered by the Frasch Process: superheated water pumped down into deposit, melting the

sulfur and forcing it up the recovery pipe with the water

Frasch Process

Natural surface Sulfur Deposit


A Sulfur Deposit Melted sulfur obtained from surface

deposits by the Frasch process.

Figure 2 The Frasch Process for Recovering Sulfur from surface deposits

Important sedimentary sulfur deposits occur near Knibyshev, Sukeievo, and Chekur in Russia. The occurrences consist of thin gypsum beds with layers of pure sulfur, laminations of sulfur and calcite, or sulfur nodules in bituminous limestone. Celestite (SrSO4) is an unusual associate.


Sulfur Mining

Sulphur Mine, Kawah Ijen Volcano, Java, Indonesia

On Earth, elemental sulfur can be found near hot springs and volcanic regions in many parts of the world, especially along the Pacific Ring of Fire; such volcanic deposits are currently mined in Indonesia, Chile, and Japan.

A man carrying sulfur blocks from Kawah Ijen, a volcano in East Java, Indonesia, 2009

USAGE • Elemental sulfur is used in Black gunpowder, Matches, and Fireworks; in

the vulcanization of rubber; as a fungicide, insecticide, and fumigant; in the manufacture of phosphate fertilizers; and in the treatment of certain skin diseases.

• The principal use of sulfur, is in the preparation of its compounds, such as: Sulfuric acid. Sulfur dioxide, used as a bleaching agent, disinfectant, and

refrigerant; Sodium bisulfite, used in paper manufacture; carbon disulfide, an

important organic solvent; Hydrogen sulfide, sulfur trioxide, used as reagents in chemistry; Epsom salts (magnesium sulfate), used as a laxative, bath additive,

exfoliant, and magnesium supplement in plant nutrition; the numerous other sulfate compounds; and sulfa drugs.

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The solution, transportation, and deposition of calcium and magnesium carbonate give rise to deposits of limestones, dolomite, and magnesite. The calcium is derived from the weathering of rocks and is transported to

the sedimentary basins chiefly as the bicarbonate, in part as carbonate, and as sulfate. Calcium carbonate (CaCO3) is deposited :

at all Eh conditions but mostly at higher pH values. by organic and mechanical means. by the photosynthesis of plants.

Carbon dioxide plays a dominant role in inorganic processes because the solution of the calcium carbonate in the sea is dependent upon it. If it escapes, calcium carbonate is precipitated Organic deposition is brought about by Algae, Bacteria, Morals, and Foraminifera.

Entire limestone beds may consist of Foraminifera or Nummulite shells, Coral, or larger fragmental shell formed mainly in shallow waters.

The deposition has been brought about by chemical precipitation with subsequent dehydration.

Ca2+ + CO32- CaCO3

8) Calcium Carbonate Deposits


Limestones Limestones

Limestones are non-clastic rock formed either chemically or due to precipitation of calcite (CaCO3) from organisms usually (shell) {Limestones are commonly containing abundant marine fossils}.

Limestones are the most common type of chemical sediment forming today by evaporation and biogenic processing of seawater.

Limestones are of marine or freshwater origin, and magnesium may in part replace the calcium, giving dolomitic limestones even though dolomite is also of primary origin. Impurities of silica, clay, or sand are commonly present, as well as minor amounts of phosphate, iron, manganese, and carbonaceous material.

Limestones formed by chemical precipitation are usually fine grained, whereas, in case of organic limestone the grain size vary depending upon the type of organism responsible for the formation Chalk: which is made up of Foraminifera is very fine grained Fossiliferous Limestone: which medium to coarse grained, as it is formed out of cementation of

Shells.

Coquina: larger fragmental shell formed mainly in shallow waters

Dolomite (or dolostone) is created by replacement of calcium by magnesium after shallow burial of limestone. Dolomite usually forms in tropical shallow marine environments.

Used Limestone, the source material for all lime based value added products – calcined. Limestone is widely used as a building construction material –concrete, blocks. Limestone is used in the manufacture - cement and glass. Limestone is used to strengthen and stabilize the sub-grade in road construction. Limestone is an alkali and is used extensively to neutralize acids – PH control. Paper, plastic, paint and rubber producers use calcium carbonate as a way to improve quality and lower

manufacturing costs.


Calcium Carbonate Deposits Non-fossiliferous Limestone Fossiliferous Limestone

Fossiliferous

Limestone

Non-fossiliferous

Limestone

Oolitic Limestone

Oolitic LS Dunes,

Bahamas

Biogenic Inorganic, ~clastic

Chemical and biochemical sedimentary Calcium Carbonate

Limestones – composed of calcite

Travertine Coquina

9) SILICEOUS SEDIMENTARY DEPOSITS (CHERTS)

Introduction Chert is the general term for very fine-grained, dense, very hard rocks and nonporous

sedimentary rocks that consist mostly or entirely of silica (SiO2), in the form of either amorphous silica or microcrystalline quartz presumably derived from recrystallization of amorphous silica. The crystal size of quartz in recrystallized chert is usually in the range 5–20 μm. Thin-section studies don’t help much because the quartz is too fine. Electron microscopy of fractured surfaces shows the quartz to be polyhedral, equant to

elongate, and closely fitted to surrounding grains. Cryptocrystalline geometries in the transition from amorphous silica to recrystallized quartz are complex.

Chert comes in two distinct varieties, nodular chert and bedded chert The relative importance of nodular chert and bedded chert has changed through

geologic time: bedded chert is much more common in the Precambrian, and nodular chert is more common in the Phanerozoic.

White and red chert interlayered with

hematite, Soudan Iron Formation

Chert nodules in Limestone

8) SILICEOUS SEDIMENTARY DEPOSITS (CHERTS)


Terminology Here are a few terms for kinds of amorphous silica and chert:

Amorphous silica:

material composed of relatively pure SiO2 but with only very local crystallographic order.

includes various kinds of hydrated and dehydrated silica gels, silica glass, siliceous sinter formed in hot springs, and (certainly of greatest

geological importance) the skeletal materials of silica-secreting organisms .

Opal (or opaline silica)

is a solid form of amorphous silica with some included water (i.e., hydrated metastable quartz that makes up tests of siliceous organisms).

is abundant in young cherts, back into the Mesozoic.

Its geological occurrence is by alteration of volcanic ash, precipitation from hot springs, and, by far most importantly, precipitation as skeletal material by certain silica-secreting organisms (see a later section).

Opal starts out as what is called Opal-A, which shows only a very weak x-ray diffraction pattern, indicating that any crystallographic order

is very local. With burial, during the initial stage of diagenesis, opal-A is transformed into Opal-CT, which shows a weak x-ray diffraction

pattern characteristic of cristobalite another silica mineral; see below). Upon further diagenesis, opal-CT is transformed into crystalline quartz, resulting in chart that consists of an equant mosaic of microquartz crystals. By that stage, most or all of the fossil evidence of origin

is obliterated.

Chalcedony (fibrous silica)

is a very finely crystalline form of silica consisting of radiating needles or fibers, often spherulitic, of quartz.

sheaf like bundles of radiating extremely thin crystals of about 0.1mm in length

There’s probably amorphous silica in among the needles, and a variable water content.

This stuff is metastable with respect to ordinarily crystalline quartz, but it hangs around a long time; it’s found even in Paleozoic cherts.

Granular microquartz: consists of nearly equi-dimentional grains of quartz. Grain sizes range from ~1 to 50 microns

Megaquartz: elongated grains greater than 20 microns in length.

Flint is the general-language equivalent of chert, usually applied to dark gray chert in nodules or as beds. The non-scientific equivalent term is flint.

Jasper: chert that’s red because it contains hematite (often more than a few percent).

Porcelanite (also spelled porcellanite): a minutely porous form of chert with a dull appearance on the fresh surface 6 November 2014 Prof. Dr. H.Z. Harraz Presentation Nonmetallic Deposits 53

From Boggs, Principles of Sedimentology

and Stratigraphy, 4th ed., p. 214


Siliceous sediment experience a predictable transformation from amorphous opal to chalcedony and eventually to microcrystalline quartz due to time/temperature dependant chemical reaction

Microquartz and megaquartz

From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed., p. 207, p209, P.210

Diatoms in deep sea sediment

Nodular chert


1) Nodular Cherts

Nodular Chert; diagenetic origin (typical): Silica derived from the solution of siliceous fossil material in predominantly carbonate rich successions (Sponge spicules and other siliceous bioclasts)

are widespread as nodules in limestone.

Are more common in the Phanerozoic. are varied in shape, from more or less regular discoidal or egg-shaped bodies (that’s the common shape for relatively

small chert nodules) to highly irregular knobby and warty bodies (the common shape of relatively large chert nodules).

Their size ranges from a few centimeters to a few tens of centimeters.

tend to be concentrated along certain bedding planes. Where abundant, they often form a two-dimensionally or three-dimensionally interconnected network.

are usually structureless, but some show faint traces of stratification coincident with that in the enclosing limestone.

Origin: Although in the past some geologists believed that nodules form by direct precipitation of silica gel on the ocean bottom, today the evidence for a replacement origin is considered to be overwhelming:

irregular shape and interconnectedness of many nodules;

presence of irregular patches of limestone in nodules;

association of chert and silicified fossils in many limestones;

presence of replaced fossils in some nodules;

traces of bedding passing through nodules;

contacts of nodules passing through fossils.

Source of the silica: the nodules can be explained by the presence of abundant biogenic amorphous silica in the original sediment and then diagenetic reorganization.

By diagenetic reorganization is meant the process by which the disseminated bodies of opaline silica (sponge spicules, diatoms, radiolarians) are dissolved, whereupon the silica in solution migrates to certain places in the sediment where it is reprecipitated in the form of opal-CT to form the nodules. This happens because the pore fluids are undersaturated with respect to the original biogenic silica, which consists of opal-A, but are supersaturated with respect to opal-CT, which has lower solubility than opal-A.

Where the chert nodules form only a small part of the bulk volume of the rock, a good case can be made that the silica that forms the nodules was present in the sediment from the time of deposition. But how about when the chert forms the greater part of the rock? Then a stronger case could be made for introduction of silica in solution after deposition, by circulating pore solutions.

Chert varieties:


2) Bedded Cherts Chert is also found as continuous beds, from centimeters up to as much as a few meters thick, often,

but not always, interbedded with shale. Bedded cherts are also often interbedded with turbidite sandstones and submarine volcanics. Most such bedded cherts show abundant evidence of having been deposited in the deep ocean. Two

scenarios seem most attractive for explaining these cherts: Open-ocean siliceous ooze is conveyor-belted to subduction margins and incorporated into a

subduction mélange. Siliceous sediment is deposited near a subduction margin, interbedded with subduction-zone

volcanics . Here we need to distinguish between Phanerozoic bedded cherts and Precambrian bedded cherts.

Phanerozoic bedded cherts: usually contain radiolarians, and they can be explained by lithification and diagenesis of radiolarian-rich bottom sediments, although some may have been inorganically precipitated with radiolarians as a nonessential constituent.

Precambrian bedded cherts: show no convincing evidence of having started out as biogenic sediment, in as much as no

silica-secreting marine organisms are known from the Precambrian. Most Precambrian cherts seem have been inorganically precipitated, although the

processes involved are not entirely clear. It’s common; cherts interbedded with chemically precipitated Ironstones. Some of the very oldest sedimentary rocks, in greenstone terranes, are bedded cherts. Chert is characteristically interbedded, down to centimeter scale, with Precambrian Iron

Formations (Ifs).


Silica Geochemistry The solubility of quartz in pure water is very small, several parts per million.

Figure 1 shows a graph of quartz solubility as a function of pH. You can see that the solubility of quartz is very low for pH values up to about 8 (slightly alkaline) but then rises sharply with increasing pH. It’s hard to measure, but it can be calculated. Moreover, attainment of equilibrium is very slow.

The solubility of amorphous silica is an order of magnitude higher, and attainment of equilibrium is also slow, but much faster than for quartz. The dominant species of silica in solution in natural waters in the usual range of pH is silicic acid, H4SiO4, a weak acid. At room temperature and pressure, amorphous silica is metastable with respect to quartz, but precipitates formed from supersaturated solutions are always amorphous silica. This is because the building of the quartz crystal structure at low temperatures takes a very long time. Solutions unsaturated with respect to amorphous silica but supersaturated with respect to quartz remain stable for many years if not longer. Clear crystalline quartz can’t be precipitated in the laboratory at the low temperatures and pressure of sedimentary environments. Presumably nature can do it because of the longer times involved.


Pathways of silica transformation after

deposition

From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed.,

p. 214

Silica stability vs. pH

From Boggs, Principles of Sedimentology and Stratigraphy,

4th ed., p. 214

Very low


Sources of silica in marine water The concentrations of dissolved silica in rivers, streams, and lakes are a few tens of parts per million. Concentrations are also in this range in groundwater; the deeper the groundwater, the higher the silica

concentration. What are the sources of silica in solution? weathering of silicate minerals: this is the ultimate source of most of the silica in solution in the

Earth’s surface waters. thermal springs: the concentration of dissolved silica concentration is very high but the absolute

volume is small. dissolution of amorphous silica: this must be important in areas underlain by silica-containing

sedimentary rocks, but it is certainly not as important overall as weathering of silicates dissolution of quartz: most natural fresh waters are in the pH range for which the solubility of quartz

is very low, so dissolution of quartz is not an important source of silica in solution. Here’s the bottom line: it’s generally agreed that by far the greater part of dissolved silica comes from weathering of silicate minerals in source rocks.

The concentration of dissolved silica in the oceans is surprisingly and extremely small: only a few tenths of a part per million. In the present oceans, there’s no possibility of precipitating silica inorganically. The reason for this very low silica concentration in the oceans is that several kinds of organisms are very effective in extracting silica from sea water and fixing it in the form of opaline silica in their skeletons. They do this out of equilibrium, by metabolic concentration processes.


Origin of Chert

Extraction from seawaters

Inorganic extraction is unlikely in unsaturated

waters like those of the ocean. However, it may

be possible in local basin saturated in SiO2 due to

dissolution of volcanics.

Biogenic extraction appears to be the only large

scale mechanism for silica extraction from the

seawater. Diatoms are largely responsible during

the present, whereas radiolarians extracted more

during the Jurassic and earlier periods.

Nodular or other replacement chert are formed

during diagenesis where they replace carbonates

and clays.


10) PHOSPHITE ORE DEPOSITS


Introduction Phosphorus is dissolved from the rocks, some of it enters the soil from which it is abstracted by

plants, from them passes into the bodies of animals, and is returned via their excreta and bones to

accumulate into deposits.

These in turn may undergo re-solution; reach the sea, and there the phosphorus deposited or

accumulated by sea life, embodied in sediments, and returned to the land upon uplift, when a new;

cycle may start.

Phosphates are soluble in carbonated water and, in the absence of calcium carbonate, will stay in solution. The phosphate in limestones resists solution.

Some phosphoric acid in reaches the sea, where it is extracted by organisms; some is re-deposited

as secondary phosphates, which may be re-dissolved; and some is retained in the soil.

Swamp waters rich in organic matter also dissolve phosphates, and some phosphorus compounds

are thought to enter solution as colloids.

Phosphorus is probably transported by streams as phosphoric acid and as calcium phosphate (some is transported by birds and animals).

Economic beds of phosphate are formed under marine conditions in the form of phosphorite.

The beds range in age from Cambrian to Pleistocene.

They are interstratified with other sediments and grade laterally into them.

Calcite and glauconite are usually found in the mineral paragenesis with phosphorite, occasionally

chlorite and siderite, and in the case of nodular deposits, also organic matter.


Types of Phosphorite Deposits:

Phosphate deposits are of three main types:

1) Guano (or Guano Bird ; or Island Deposits): These are ancient and/or fossil deposits of bird or bat excreta.

Bird and bat excrement that has been leached to form an insoluble residue of calcium phosphate.

Guano deposits from birds are most commonly found on oceanic islands, especially abundant- like

some South Pacific Islands.

Guano deposits from bats are found in large cave systems.

Guano deposits need a dry climate for their preservation.

2) Igneous Phosphate deposits : Phosphate deposits are 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. 3) Sedimentary Phosphate Deposits


Sedimentary Phosphorites

Mining guano in the Chincha Islands off the central coast of Peru ~1860

The nest of the Peruvian Booby is made of almost pure guano.

Igneous Phosphate deposits


Economic and potentially economic phosphate deposits of the world

www. Ifdc.org


3) Sedimentary Phosphate Deposits Sedimentary phosphorites are Organic/Chemical Sedimentary Rocks that contain more than 15% P2O5 or 6.5% phosphorus (P).

are mined from rocks, usually shales, dolomite, or limestones, that contain unusually high concentrations of the mineral apatite {Ca5(PO4)3(F, OH, Cl, ½ CO3)}. Sometimes it is mixed with enough calcite or clay to be limestone or shale.

Sometimes, this is nearly pure apatite, in which case it is called ―phosphorite” (i.e., Phosphorite is a commonly used term for lithified phosphate rock).

Immense quantities of phosphate rock or phosphorite occur in sedimentary shelf deposits, ranging in age from the Proterozoic to currently forming environments.

are commonly interbedded with marine shale, limestone, and dolomite.

have textures that resemble limestones.

may be made up of peloids, ooids, bioclasts and clasts that are now composed of apatite.

Common names: Rock phosphate, phosphates

Implies a marine origin

Form in restricted areas near continental margins: where deep ocean currents are upwelling.

Phosphorus is a limiting nutrient in many marine and fresh water ecosystems: limits primary productivity.

Very little phosphorus is supplied to the oceans by river inflow.

When phosphorus is supplied by upwelling from the deep ocean, productivity skyrockets.

A rain of phosphate-rich skeletal debris falls to the ocean floor.

Distinguished by chocolate brown color, may have pellets, lumps or nodules (mm scale)

Marine deposits often have nodules.

Deposits can be extensive (Ex: The Phosphoria Formation in Utah is phosphate-rich shale). Sedimentary phosphate deposits are of three main types:

a) Bone Beds (Bioclastic)

Composed largely of vertebrate skeletal fragments.

These are localized accumulations of fossil deposits of bone, teeth, scales and excreta (i.e. coprolites) that are occasionally thick enough to form economic deposits.

These have mostly been mined in the past. A good example of bone beds is the marsupial-rich bone phosphate deposits of the Wellington Caves near Dubbo, New South Wales.

b) Nodular:

Spherical to irregularly shaped nodules, with or without internal structure, often containing grain, pellets or fossils.

c) Pebble-bed:

The sandstone equivalent-composed of nodules, fragments or phosphatic fossils that have been mechanically concentrated by reworking of earlier formed phosphate deposits.

All marine sediments, particularly limestones, contain some phosphate, which under particular conditions may rise to a greater concentration than normal (phosphatic limestone), but rarely reaching an economically extractable concentration.

These deposits are rare and usually arise from either the leaching of the phosphatic limestone (dissolving away the calcium carbonate and leaving behind the detrital phosphate) or the extraction of phosphate at higher levels followed by secondary concentration from downward-percolating groundwaters

These deposits occur under relatively cool conditions in an oxygen-free environment.


Mineralogy and Mineral Composition of Sedimentary Phosphorite Deposits

The mineralogy of phosphate deposits is very complex. They usually consist of fine-grained mixtures of various calcium phosphates with the

most common mineral being varieties of apatite and related minerals {Ca5(PO4)3F}. Collophane is an amorphous calcium phosphate that is also commonly found in

phosphate deposits. Mineral composition of phosphorite deposits: is determined by the phosphorite

which is a composite chemical compound of calcium phosphate, calcium fluoride, and calcium carbonate of the type of nCa3(PO4)2.nCaF2.KCaCO3.

Three fractions can be distinguished:

1) fluor-apatite {3Ca3(PO4)2CaF2} 2) carbonate-apatite {3Ca3(PO4)2CaCO3}; and 3) hydroxyl-apatite {3Ca3(PO4)2Ca(OH)2}.

Most are carbonate hydroxyl fluorapatites (a.k.a.: francolite) (Ca10(PO4,CO3)6F2-3) in which up to 10% carbonate ions can be substituted for phosphate ions.


Amblygonite Lazulite Pyromorphite Vivianite Torbernite

Autunite Xenotime Monazite Turquoise

Variscite Apatite Herderite Wavellite


Phosphates form in shallow marine

environments where dissolved PO4-3 is carried

by upwelling of deep ocean water.

These areas are biologically productive -

many fossils are found, especially bone

material.

Inhibition of organic mater decay due to

reducing conditions at ocean floor.

Interstitial water exhalation

Phosphatization: where phosphate replaces

skeletal and carbonate grains during

diagenesis.

Origin of Phosphorites

From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed.,

p. 229

Phosphate accumulation is associated with oceanic upwelling (cold, oxygen and nutrient rich bottom waters coming to the surface, as happens off Peru). Under such conditions, there is a great profusion of life, and consequently death. Organic remains (soft-body parts, bones, fecal matter)

sinks to the bottom. The great abundance of incoming organic matter may

overwhelm the ability of bottom organisms to consume this rain of food, and some goes undigested.

Under anaerobic conditions, the reduced organic matter remains.

Under slightly more oxidizing conditions, the reduced organic matter gets consumed, but the phosphate remains.

Under normal oxidizing conditions, the phosphate gets consumed or dissolved into seawater.

Figure Schematic illustration of processes that form phosphate deposits in the marine environment

Figure Schematic illustration of the formation of Phosphorites in areas of upwelling on the open ocean shelves.

Main features of a simplified genetical model for Egyptian phosphorites

Worldwide occurrence of phosphatic deposits

From Boggs, Principles of Sedimentology and Stratigraphy, 4th ed., p. 224


World Phosphate Rock Production and Demand-World Phosphate


Use of Phosphate

• 90% of all phosphates is used as fertilizer, 10% used for animal feedstuff, detergents, food

and drink products, fire extinguishers, dental products, and surface treatment of metals.

• Phosphates were once commonly used in laundry detergent in the form trisodium

phosphate (TSP).

In agriculture, phosphate is one of the three primary plant nutrients, and it is a component of fertilizers. In former times, it was simply crushed and used as is, but the crude form is now used only in organic farming. Normally, it is chemically treated to make superphosphate, triple superphosphate, or ammonium phosphates, which have higher concentration of phosphate and are also more soluble, therefore more quickly usable by plants.

Phosphate compounds are occasionally added to the public drinking water supply to counter plumbosolvency.

The food industry uses phosphates to perform several different functions ( For example, in meat products, it solubilizes the protein). This improves its water-holding ability and increases its moistness and succulence. In baked products, such as cookies and crackers, phosphate compounds can act as part of the leavening system when it reacts with an alkali, usually sodium bicarbonate (baking soda).

Phosphate minerals are often used for control of rust and prevention of corrosion on ferrous materials, applied with electrochemical conversion coatings

Phosphoric acid and Chemical reagents


http://en.wikipedia.org/wiki/Detergent

http://en.wikipedia.org/wiki/Trisodium_phosphate

http://en.wikipedia.org/wiki/Trisodium_phosphate

http://en.wikipedia.org/wiki/Agriculture

http://en.wikipedia.org/wiki/Plant

http://en.wikipedia.org/wiki/Fertilizer

http://en.wikipedia.org/wiki/Organic_farming

http://en.wikipedia.org/wiki/Superphosphate

http://en.wikipedia.org/wiki/Triple_superphosphate

http://en.wikipedia.org/wiki/Ammonium_phosphate

http://en.wikipedia.org/wiki/Soluble

http://en.wikipedia.org/wiki/Plumbosolvency

Relationship of Phosphate Rock and Phosphate Fertilizers


11) EVAPORITE DEPOSITS

EVAPORITE DEPOSITS Evaporite deposits are formed by evaporation of lake water or seawater.

Evaporite is a name for a water-soluble mineral sediment (i.e. chemical sediment) that result originally

precipitated from saline (brine) solutions concentrated and crystallization by solar evaporation from an

aqueous solution.

Evaporite deposits that are composed of minerals that originally precipitated from saline (brine) solutions

concentrated by solar evaporation.

Evaporite Considered as Inorganic/Chemical Sedimentary Rock types:

―Chemical‖: derived from the precipitation of dissolved minerals in water.

―Inorganic‖: minerals precipitate because of evaporation and/or chemical activity.

Evaporites form in a variety of settings:

Most evaporites are derived from bodies of sea water or a saline inland lake experiences net

evaporation, the concentration of the ions dissolved in that water rises until the saturation point of

various materials is exceeded, and minerals precipitate or crystallize.

There are two types of evaporite deposits: namely Buried evaporite deposits and Brine evaporite

deposits.

Brine Evaporite deposits (found??) in both Marine and Non-marine environments:

Minerals precipitated from ―super-saturated‖ saline water in enclosed basin environments under dry arid conditions with high evaporation rates (e.g., Playa lakes). Playa lake basins between mountain ranges, especially in Basin and Range Province.


Evaporation has been important in producing many valuable types of non-metallic mineral deposits.

Evaporites are excellent indicators of paleoclimate: it takes a hot and arid climate for major evaporite

deposits to form. Evaporite deposits are known from all the continents, with ages ranging from

Precambrian to Late Cenozoic (although Precambrian evaporites are scarce, either because they

were not deposited or because they have been dissolved away during diagenesis through geologic

time).

Extracted by Solution mining techniques (or Frasch Process)

Two wells

Selective dissolution

Hot leaching

1) Buried deposits : Evaporite deposits that formed during various

warming Seasonal and climatic change periods of

geologic times.

Like: Shallow basin with high rate of

evaporation – Gulf of Mexico, Persian Gulf, ancient Mediterranean Sea, Red Sea

The most significant known evaporite depositions happened during the Messinian salinity crisis in the basin of the Mediterranean

2) Brine deposits: Evaporite deposits that formed from evaporation:

Seawater or ocean (Ocean water is the prime source of minerals formed by evaporation) . Then, solutions derived

from normal sea water by evaporation are said to be hypersaline

Lake water

Salt lakes

Playa lake

Springs

Extracted by Normal evaporation techniques

Pond Marsh

Evaporite deposits

http://en.wikipedia.org/wiki/Messinian_salinity_crisis



http://en.wikipedia.org/wiki/Mediterranean

Brines form by strong evaporation. These ponds on the shores of Great Salt Lake are sources of magnesium as well as salt.

Water well drilling on the western portion of Allana Potash license, Dallol Project-Ethiopia

Potash salt and halite crystallization in pilot test evaporation ponds

KCl

The formation of the potash deposits (Barrier theory“)

http://www.k-plus-s.com/en/wissen/kalivorkommen-barrentheorie.gif

Environments

Marine: Coastal Mud flats – Sabkhas Salt pans Barred basins

Continental: Salt lakes

Springs

ENVIRONMENTS FOR EVAPORITE PRECIPITATION

Volumetrically, each can be significant:

1) Coastal evaporites

Form in a Sabkha environment: A coastal, supratidal mudflat

Evaporites do not precipitate directly from seawater

Evaporites replace other material (mineral) in the shallow subsurface

Marine processes dominate

One of the most interesting areas to sedimentologists

Forms many oil traps

Also provides one model for dolomite formation

2) Eolian/interdune

Between sand dunes and ridges

3) Continental: Sabkha/playa

Shallow saline lakes

Note: these models don’t explain all evaporites

The importance of shallow vs. deep water is still debated

A problem: To deposit 2000 m of evaporite, you would need to evaporate a LOT of seawater!!

Ex: Evaporation of the entire Mediterranean Sea would only produce 60 m of evaporites

So: We need models or mechanisms that can replenish the supply of ions

The most significant known evaporite depositions happened during the Messinian salinity crisis in the basin of the Mediterranean.




http://en.wikipedia.org/wiki/Mediterranean

Compared between Marine and Non-marine evaporites Marine evaporites Non-marine evaporites

Marine Environments:

Coastal

Mud flats – Sabkhas

Salt pans

Barred basins

can be described as ocean or sea water

deposits (solutions derived from normal sea

water by evaporation are said to be

hypersaline)

Shallow basin with high rate of evaporation:

e.g. Gulf of Mexico, Persian Gulf, ancient

Mediterranean Sea, and Red Sea.

The most important salts that precipitate from

sea water: Gypsum, Halite, and Potash salts

{Sylvite (KCl), Carnallite (KMgCl3 * 6H2O),

Langbeinite (K2Mg2(SO4)3), Polyhalite (K2Ca2Mg(SO4)6 *

H2O), Kanite (KMg(SO4)Cl * 3H2O), and Kieserite

(MgSO4)}

Marine evaporite deposits are widespread.

In North America, for example, strata of

marine evaporites underlie as much as

30% of the land area.

Marine evaporites produce:

Most of the salt that we use.

The gypsum used for plaster.

Continental Environments:

Salt lakes

Saline Inland lakes Playa lakes

Inland lakes

Groundwater Springs

Saline lakes includes things such as:

Perennial lakes, which are lakes that are there year-round;

or

Playa lakes, which are lakes that appear only during

certain seasons,

Examples of modern non-marine depositional environments

include the Great Salt Lake in Utah and the Dead Sea, which lies

between Jordan and Israel.

The layers of salts precipitate as a consequence of evaporation:

Salts that precipitate from lake water of suitable composition

include: Sodium carbonate (Na2CO3), Sodium sulfate

(Na2SO4), and Borax (Na2B4O7.1OH2O).

Borax and other boron-containing minerals are mined from

evaporite lake deposits in Death Valley and Searled and Borax

Lakes, all in California; and in Argentina, Bolivia, Turkey, and China.

Huge evaporite deposits of Sodium carbonate were laid down in the

Green River basin of Wyoming during the Eocene Epoch. Oil shales were also deposited in the basin.

The most important salts that precipitate from lake: Blödite, Borax

(Na2B4O7.1OH2O), Epsomite (MgSO4.7H2O), Gaylussite,

Glauberite, Mirabilite, Thenardite and Trona

(NaHCO3.Na2CO3.2H2O).

Non-marine deposits may also contain Halite, Gypsum, and

Anhydrite, and may in some cases even be dominated by these

minerals, although they did not come from ocean deposits.

Mediterranean Evaporates

Evaporation proceeds most rapidly in warm, arid climates. In the evaporation of bodies of saline water, concentration of the soluble salts occurs, and when super-saturation of any salt is reached, that salt is precipitated.

Deposition of minerals by evaporation is dependent on factors:

1) Solubility contents,

2) Temperature,

3) Pressure,

4) Depositional environment, and

5) Seasonal and climatic changes.

PROCESS OF MINERAL FORMATION BY

EVAPORATION

The potash and salt deposists worldwide

Quelle: K+S Käding/Beer


http://www.k-plus-s.com/en/wissen/kalivorkommen-map.gif

1) Chemistry of Seawater

The first step toward looking at evaporites

Source of evaporites: is seawater Ocean water is the prime source of minerals formed by

evaporation.

Dissolved Species - Seawater NaCl is most abundant because of compostion of seawater:

Includes all dissolved ions ~34.7 ppt

Most common ions: Cl-, Na+, Mg 2+, SO42-, Ca2+, K+...

Trace components: Br, F, B, Sr

85.65 % Na2+ and Cl- ions

remaining solutes 14.35%

About 3.45% of seawater consists of dissolved salts of which 99.7% by weight is made up of only seven, ions that are as listed below :-

These components of seawater can all contribute to evaporite mineralization.

Na+ 30.61 Cl- 55.04

Mg2+ 3.69 SO42- 7.68

Ca2+ 1.16 HCO3- 0.41

K+ 1.10

CHEMISTRY OF EVAPORITES

Dissolved Species - Rivers

• Main dissolved species in freshwater is Ca, CO3 and SiO4

6 November

2014


Evaporation of Seawater In terms of volumes of precipitated salts, experiments like that show that if a column of sea water 1000 m thick is evaporated to dryness, the precipitated salt deposit would be about 17 m thick.

Of this, 0.6 m would be gypsum, 13.3 m would be halite, and the rest, 2.7 m, would be mainly salts of potassium and magnesium.

But is this how most evaporite deposits are formed?

1000 m (1 km) of seawater will produce

17 m of evaporites

ppt. sequence controlled by

solubility – least soluble first

0.1 m CaCO3

0.6 m gypsum

13.3 m NaCl

3 m KCl, KMgCl


Volume of

water

remaining Evaporite Precipitated

50%

At this point, minor carbonates

begin to form.

A little iron oxide and some

aragonite are precipitated.

Minor quantities of carbonate

minerals (Calcite and dolomite)

form.

a) Calcite(CaCO3):

Precipitates if < 50% of seawater is

removed.

Only accounts for a small % of the total

solids

20%

Gypsum precipitates:

Gypsum (<42°C) or Anhydrite

(>42°C).

b) Gypsum:

Precipitates if 80-90% of seawater has

been removed

Solution is denser

10% Rock salt (halite) precipitates

c) Halite:

Precipitates if 86-94% of original seawater

has been removed

Brine (solution) is very dense

5%

Mg & K salts precipitate

Precipitation of various

magnesium sulfates and chlorides,

and finally to NaBr and KCl.

Potassium and magnesium salts

(kainite, carnallite, sylvite)

d) Potassic salts:

Precipitate if > 94 % of original seawater

has been removed

So: ionic strength (potential) of

evaporating seawater has a strong control

over minerals that form

Inc

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sin

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va

po

rati

on

Ra

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The first phase

De

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Economic importance of evaporites Halite- rock salt for roads, refined into table salt

Thick halite deposits are expected to become an important location for the disposal of nuclear waste because of their geologic stability, predictable engineering and physical behaviour, and imperviousness to groundwater.

Gypsum- Alabaster: ornamental stone; Plaster of Paris: heated form of gypsum used for casts, plasterboard, … etc.; makes plaster wallboard.

Potash- for fertilizer (potassium chloride, potassium sulfates)

Evaporite minerals, especially nitrate minerals, are used in the production on fertilizer and explosives.

Salt formations are famous for their ability to form diapirs, which produce ideal locations for trapping petroleum deposits.

Evaporite minerals start to precipitate when their concentration in water reaches such a level that they can no longer exist as solutes.

The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is

Calcite (CaCO3) and dolomite (CaMg(CO3)2)

Gypsum (CaSO4-2H2O) and anhydrite (CaSO4).

Halite (i.e. common salt, NaCl)

Potassium and magnesium salts

The abundance of rocks formed by seawater precipitation is in the same order as the precipitation given above. Thus, limestone (calcite) and dolomite are more common than gypsum, which is more common than halite, which is more common than potassium and magnesium salts.

Evaporites can also be easily recrystallized in laboratories in order to investigate the conditions and characteristics of their formation.

Major groups of evaporite minerals More than eighty naturally occurring evaporite minerals

have been identified. The intricate equilibrium relationships among these minerals have been the subject of many studies over the years. This is a chart that shows minerals that form the marine evaporite rocks, they are usually the most common minerals that appear in this kind of deposit.

Hanksite, Na22K(SO4)9(CO3)2Cl, one of the

few minerals that is both a carbonate and a

sulfate

Mineral

class

Mineral

name

Chemical

Composition Rock name

Halites

(or

Chlorides)

Halite NaCl Halite; rock-salt

Sylvite KCl

Potash Salts

Carnallite KMgCl3 * 6H2O

Kainite KMg(SO4)Cl * 3H2O

Sulfates

Polyhalite K2Ca2Mg(SO4)6 * H2O

Langbeinite K2Mg2(SO4)3

Anhydrate CaSO4 Anhydrate

Gypsum CaSO4 * 2H2O Gypsum

Kieserite MgSO4 * H2O --

Carbonates

Dolomite CaMg(CO3)2 Dolomite,

Dolostone

Calcite CaCO3 Limestone

Magnesite MgCO3 --

http://en.wikipedia.org/wiki/Hanksite

Calcium Sulfate Deposition

Calcium sulfate may be deposited either in the form of gypsum (<42°C) or anhydrite (>42°C), depending upon the temperature, pressure, and salinity of the solution.

Occurs as part of the evaporite succession (Sequence of formation of evaporites: Calcite dolomite gypsum halite sylvite Mg – salts).

The first salts to separate by the evaporation of seawater are carbonates.

When the water has been evaporated to about 20% of its original volume, calcium sulfate starts to separate. At the temperatures of evaporation of marine basins, much gypsum will always be deposited first if the temperature is <42°C, and that marine beds of pure anhydrite imply either that the early deposited gypsum was converted to anhydrite or that deposition occurred above the conversion temperature of >42°C.

Equilibrium temperature for the reaction CaSO4*2H2O CaSO4 + 2H2O(Liq. Sol.)

is a function of activity of H2O of the solution. Anhydrite can be hydrated back to gypsum

upon uplift and exposure to low-salinity surface waters.

Resulting Products.

Calcium sulfate deposition occurs in: 1) Beds of relatively pure gypsum or

anhydrite from a few meters to many hundreds of meters in thickness (gypsum beds constitute one of the most important nonmetallic resources and anhydrite finds little use);

2) Gypsum beds with impurities of anhydrite;

3) Alabaster, massive fine-grained white or lightly tinted variety of gypsum and

4) Gypsite, an admixture with dirt. 5) The beds are generally interstratified

with limestone or shale, and they are commonly associated with salt.


Gypsum Uses: Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4·2H2O).

Gypsum is used in a wide variety of applications:

Gypsum board is primarily used as a finish for walls and ceilings, and is known in construction as drywall, sheetrock or plasterboard.

Gypsum blocks used like cement blocks in building construction.

Plaster ingredient (surgical splints, casting moulds, modeling)

Plaster of Paris: heated form of gypsum used for casts, plasterboard, … etc.

Alabaster: ornamental stone

As alabaster, a material for sculpture, especially in the ancient world before steel was developed, when its relative softness made it much easier to carve.

A binder in fast-dry tennis court clay

Adding hardness to water used for brewing

Used in baking as a dough conditioner, reducing stickiness, and as a baked-goods source of dietary calcium. The primary component of mineral yeast food.

A component of Portland cement used to prevent flash setting of concrete

Soil/water potential monitoring (soil moisture)


Gypsum

Ca[SO4] · 2H 2O S.G. 2.312 - 2.322 Hardness 2 Color Colorless to white, often tinged other hues due to impurities; colorless in transmitted light.


Order of precipitation of common compounds 1) CaCO3 and MgCO3 are the 1st to precipitate

2) CaSO4 precipitates next (Calcium all precipitated). Leaving mostly Na and Mg cations

3) (Na2CO3) next in order precipitates if any CO3 left

4) (Na2SO4) precipitates next leaving mostly the chloride compounds

5) MgSO4 precipitates out all that is left is NaCl

6) NaCl saltern is left. These are fairly common (Great Salt Lake)

7) MgCl2 and CaCl2 lakes are rare (Called Bitterns Dead Sea).

8) If all water evaporates - bed of salt (NaCl) usually results.

Continental waters (saline lakes) and Inland brine lakes evaporation:

Epsomite {or Epsom salts} (MgSO4.7H2O

Borax (Na2B4O7·10H2O or Na2[B4O5(OH)4]·8H2O)

Trona (NaHCO3.Na2CO3.2H2O)

Natron (Na2CO2.10H2O)

Pre

cip

itati

on

seq

uen

ce

EVAPORATION SEQUENCE OF CONTINENTAL WATERS AND INLAND LAKES


Lakes Seawater

1) Calcite (CaCO3) and Magnesite (MgCO3) 1) Calcite(CaCO3) and Dolomite (CaMg(CO3 )2

2) Gypsum (CaSO4 *2H2O) precipitates next. 2) Calcium Sulfate precipitates next as Gypsum (<42°C) or Anhydrite (>42°C).

3) Na2CO3 (in form of Trona and Natron) next in order precipitates if any CO3 left

4) Na2SO4 (in form Hanksite [Na22K(SO4)9(CO3)2Cl]) precipitates next leaving mostly the chloride compounds

5) MgSO4 (in form of Epsom salts) precipitates out all that is left is NaCl

6) NaCl saltern is left. These are fairly common (Great Salt Lake)

3) Rock salt (halite) precipitates

Precipitates if 86-94% of original seawater has

been removed

Brine (solution) is very dense

7) MgCl2 and CaCl2 lakes are rare (Called Bitterns Dead Sea).

8) If all water evaporates - bed of salt (NaCl) usually results.

4) Potassic salts: Precipitate if > 94 % of original seawater has been

removed.

So: ionic strength (potential) of evaporating seawater

has a strong control over minerals that form.

Potassium and magnesium salts (Kainite, Carnallite, Sylvite)

Precipitation of various magnesium sulfates and chlorides, and finally to NaBr and KCl.

Compared between Evaporation Sequence of Seawater and Lakes

Inc

rea

sin

g E

va

po

rati

on

Ra

tes

D

ecr

eas

ing

ord

er

of

solu

bili

ty

The first

phase


Potash Deposition

Potassium is the seventh most common element occurring in the Earth’s crust, accounting for 2.4% of its mass.

Potassium present in most rocks and soils. Consequently, they are not common and important deposits.

Some of the world's supply of potash is derived from marine evaporates.

The world has an estimated 250 billion metric tons of K2O resources.

Occurrences: Sedimentary salt beds remaining from Ancient Inland Seas (evaporite deposits)

Evaporation of Salt lakes and Natural brines

Potash deposits, i.e. natural concentrations of raw potash, consist of potassium salt rock, predominantly made up of the potassium minerals:

Sylvite (KCl),

Carnallite (KMgCl3*6H2O),

Kainite (4KCl.4MgSO4.11H2O) and

Langbeinite (K2Mg2(SO4)3), or

Potassium-bearing salt solutions either underground or in salt lakes.

Flotation is one of the major methods to upgrade the potash. Normally fatty acids are used as collectors for flotation. This type of collectors is not suitable for the treatment of complex phosphate ores when calcite, dolomite present. Potash can be separated from halite by reverse flotation.

Potash is the most important source of potassium in fertilizers (potassium chloride, potassium sulfates)


Water well drilling on

the western portion of

Allana Potash license,

Dallol Project-Ethiopia

Potash salt and halite crystallization in pilot

test evaporation ponds

KCl


The formation of the potash deposits (Barrier theory―)

http://www.k-plus-s.com/en/wissen/kalivorkommen-barrentheorie.gif

World Potash Mine Production 2003

012345

6789

10

Canada

Russia

Belaru

s

Germ

any

Isra

el

Jord

an

United S

tate

s

United K

ingdo

m

Spain

China

Chile

Brazil

Ukrai

ne

Mil

lion m

etri

c to

ns,

K2O

Source: IFA

% o

f to

tal

pro

duct

ion

78% of total K2O produced

33

17 15

13

0

5

10

15

20

25

30

35


Potash Deposits in Dead Sea K extracted from Dead Sea

The world‟s largest reserve of potash in

the form of salt solutions is the Dead Sea

(up to 1 billion tonnes of K2O), which has

been used for potash production since the

beginning of the 1930s.

contains an estimated up to 1 billion

tonnes KCl

Israel and Jordon represented 11% of

world production in 2003

Today DSW operates on the Israeli side

and APC on the Jordanian side

Arab Potash, the only producer in Jordan

is being privatized

Dead Sea Works (DSW), with production

in Israel and recent acquisitions in Spain

and UK is the world‟s 5th largest producer

K2O

pro

duct

ion, „0

00 t

0

500

1000

1500

2000

2500

1994 1996 1998 2000 2002

Israel Jordan


12) SELECTED SOME NON-METALLIC

METAMORPHIC DEPOSITS


Formation of Mineral Deposits by Metamorphism

• Several kinds valuable non-metallic mineral deposits are formed from rocks chiefly by Regional metamorphism (i.e.,

• The source materials are rock constitutes that have undergone recrystallization or recombination, or both of the rock making minerals).

Rarely, water or carbon dioxide has been added, but other new constituents are not introduced as they are in contact metasomatic deposits.

The enclosing rocks are wholly or in part metamorphosed: it is the rock metamorphism that has given rise to deposits.


Non-metallic Metamorphic Minerals • Apart from metasomatism, metamorphic rocks

are not major mineral resources. • The chief deposits thus formed are: Asbestos,

Graphite, Talc, Vermiculite, Soapstone, Garnet, Emerald, Kyanite, Wollastonite, Andalusite and Sillimanite.

• Specific metamorphic minerals: Kyanite and Wollastonite for refractories Garnet for abrasives

• Ornamental stone: Marble, Quartzite, Gneiss, Schist, Serpentinite, Slate, Migmatite.


12.1) Asbestos Deposits Cancer hazard

Asbestos – what is it? Asbestos is a commercial term: Any fibrous mineral utilized in an industrial process with a 3:1 length to width

“A commercial term applied to a group of highly fibrous silicate minerals that readily separate into long, thin, strong fibers of sufficient flexibility to be woven. . .”

A collective mineralogic term that describes a variety of certain silicates belonging to the serpentine and

amphibole mineral groups, which have crystallized in the asbestiform habit causing them to be easily separated

into long, thin, flexible, strong fibers when crushed or processed.

There are two main types of asbestos minerals:

A) Serpentine asbestos (or Chrysotile Asbestos)

B) Amphibole asbestos.

Asbestos is the name applied to six naturally occurring minerals that are mined from the earth: Chrysotile, Crocidolite, Asbestiform grunerite (Amosite), Anthophyllite asbestos, Tremolite asbestos and Actinolite asbestos. The nomenclature and composition of amphibole minerals should conform with International Mineralogical Association recommendations (Leake, B.E.,

Nomenclature of Amphiboles. American Mineralogist. Vol. 82, 1019 - 1037, 1997)

The different types of asbestos minerals are:

Serpentine group:

Chrysotile (White asbestos)

Amphibole group:

Amosite (Brown asbestos)- Grunerite

Crocidolite ( Blue asbestos) - Riebeckite

Anthophyllite

Tremolite

Actinolite


Chrysotile Mg6Si4O10(OH)8

Grunerite = Amosite [Fe2Fe2+5]Si8O22(OH)2

Riebeckite = Crocidolite Na2[(Fe, Mg)3Fe3+2] Si8O22(OH)2

Anthophyllite [Mg2Mg5]Si8O22(OH)2

Tremolite Ca2Mg5Si8O22(OH)2

Actinolite Ca2(Mg4.5-2.5Fe2+0.5-2.5)Si8O22(OH)2

Asbestos – what is it? Each of these six minerals included in OSHA‟s asbestos standard occurs in both an Asbestiform

and a Nonasbestiform variety.

Three of the six minerals have been given a different name for each of their two forms. Chrysotile

is the asbestiform variety of the serpentine minerals group. In this group antigorite is a common

nonasbestiform mineral. In the amphibole group, crocidolite is the asbestiform variety of

riebeckite; amosite is the asbestiform variety of “cummingtonite”-grunerite.


Naturally occurring fibrous silicate minerals:

Wide range of useful properties have led to it being used in many products since ancient times;

Was commercially mined in many countries: Canada, South Africa, Russia, Zimbabwe, China,

USA, Italy, Australia, Cyprus …etc.

Chrysotile is the most common asbestos mineral (~90% of asbestos mined)

Asbestiform Variety Nonasbestiform Variety

Chrysotile Antigorite

Crocidolite Riebeckite

Amosite Cummingtonite - Grunerite

Asbestiform Nonasbestiform

Chrysotile Antigorite

Crocidolite Riebeckite

Amosite

Asbestiform and Nonasbestiform Varieties


A) Serpentine Asbestos (or Chrysotile Asbestos ): Chrysotile (Mg6Si4O10(OH)8) asbestos occurs in serpentine that has been altered from ultrabasic

igneous rocks, such as peridotite or dunite or magnesian limestones or dolomite; the first yields 93 % of the world's asbestos supply.

In the ultrabasic occurrences, the fiber in lens like veinlets enclosed in serpentine and has three modes of occurrence:

i) Cross-fiber, with fibers normal to walls, their length begin the width of the veinlet, or less if they contain “partings";

ii) Slipper, parallel or oblique to the walls, and long but of poor quality;

iii) Mass-fiber, composed of a mass aggregate of interlaced, unoriented, or radiating fibers.

Chrysotile fibers range up to 10 to 12 cm in length, rarely 20 cm; most of them are less than 2 cm. Chrysotile may make up from 2 to 20 %t of the rock.

Origin of Chrysotile Asbestos

Chrysotile asbestos is confined entirely to serpentine and strictly speaking, is a fibrous variety of serpentine.

Serpentinization is an autometamorphic process, and in the ultrabasic rocks, such as dunite, serpentinization has proceeded along fractures.


B) Amphibole Asbestos : The amphiboles comprise the minerals: amosite,

crocidolite, termolite, actinolite and anthophyllite. The amphibole varieties, of which crocidolite and

amosite are the most important. These two minerals are found in slates, schists and

banded ironstones over are extensive belt in Transvaal and Cape Province of South Africa.

The crocidolite deposits are said to be the most extensive asbestos deposits in the world but only make up 3.5 % of the world's asbestos market.

They are in part associated with dolerite sills.

Tremolite Ca2Mg5Si8O22(OH)2

Anthophyllite [Mg2Mg5]Si8O22(OH)2

Riebeckite = Crocidolite Na2[(Fe, Mg)3Fe3+2] Si8O22(OH)2

Grunerite = Amosite [Fe2Fe2+5]Si8O22(OH)2

Actinolite Ca2(Mg4.5-2.5Fe2+0.5-2.5)Si8O22(OH)2


Serpentine Amphibole

Structure of

Asbestos Fibers

Crystalline structure – sheet silicate

‘Scroll-like’ structure

Fibers are less straight, more flexible

and less liable to split into finer

fibers compared to the amphiboles

Crystalline structure – chain silicate

Different amphiboles distinguished by

variations in chemical composition.

Fibers are generally straighter, more

brittle and split into finer fibers more

readily than serpentine

Asbestiform Variety Chrysotile Crocidolite; Amosite

Nonasbestiform

Variety

Antigorite Riebeckite; Cummingtonite - Grunerite

Asbestos Minerals Chrysotile - White asbestos

Amosite - Brown asbestos (Grunerite) Crocidolite - Blue asbestos

(Riebeckite) Anthophyllite Tremolite Actinolite


Properties of Asbestos Fibres Industrial applications of asbestos take advantage of

a combination of properties:

Use of fibre as reinforcing material largely dependent on length of fibre,

Other properties that make asbestos useful include: Flexibility

High tensile strength

Non-combustibility

Resistance to heat

Low electrical conductivity

Resistance to chemical attack


Uses of Asbestos Widespread uses of asbestos include:

Thermal and acoustic insulation Spray coating (as fire protection) Fireproofing Artificial fireplaces and materials Asbestos reinforced building board Re-enforcing concrete, tiles Asbestos reinforced cement products Plastic products (e.g. vinyl floor tiles) Textiles Brake linings Pot holders and ironing board pads Patching and spackling compounds Wall and ceiling panels Pipe and duct insulation Building insulation Friction materials (brake pads …etc) Gaskets and packing materials Roofing felts, Roofing materials. … etc


12.2) Graphite Graphite or “Black Lead"

is soft and black, has a greasy feel, and marks paper; hence the term graphite (to write). Graphite is one of the allotropes of carbon. Unlike diamond, graphite is an electrical conductor. Graphite holds the distinction of being the most stable form of solid carbon ever discovered.

True graphite yields graphitic acid when treated with nitric acid; amorphous carbon does not. Synthetic graphite (i.e., produced from oil and anthracite coal,- new accounts for 90 % of the graphite

production). Occurrence:

Graphite occurs chiefly in metamorphic rock produced by regional or contact metamorphism. It is found in marble, gneiss, schist, quartzite and altered coal beds; It also occurs in igneous rocks, veins and pegmatite dikes. It may be considered the highest grade of coal, just above anthracite and alternatively called meta-anthracite,

although it is not normally used as fuel because it is hard to lignite. Most of the crystalline variety occurs in minute flakes disseminated through metamorphic rocks. The amorphous

variety is dust like form. The deposits may be of large size, and the graphite content may be as much as 7 %. Associated minerals are quartz, chlorite, rutile, titanite and sillimanite. Natural Graphite Occurrences as :

i) Dissemination ii) Fissure veins

Classification of Graphite:

There are three principal types of natural graphite, each occurring in different types of ore deposit: i) Crystalline flake graphite : (53%) occurs as isolated, flat, plate-like particles with hexagonal edges if unbroken

and when broken the edges can be irregular or angular (e.g., Madagascar-open pit, 410-950 $/t) ii) Amorphous graphite: occurs as fine particles, a noncrystalline, impure variety. It is debatable that the material

of graphitic slate, which yields "amorphous graphite", is really graphite or amorphous carbon. (e.g., Mexico-Underground mines, 240-260 $/t).

iii) Lump graphite (also called vein graphite): occurs in fissure veins or fractures and appears as massive platy intergrowths of fibrous or acicular crystalline aggregates, and is probably hydrothermal in origin (Sri Lanka-Underground mines).


http://en.wikipedia.org/wiki/Image:GraphiteUSGOV.jpg

USAGE Major uses:

Refractories: (High temperature applications- Melting Point 3927°C): Course flakes.

Steel Making: Amorphous graphite or fine flakes.

Expanded Graphite: Flakes.

Minor uses:

Trucks: Substitute for asbestos.

Foundry Facing and Lubricants: Amourphous or fine flakes are used High temperature dry lubricant.

Pencil Lead: Powder graphite + clay.

Zn-C Batteries: Powdered fine flaked graphite.

Electric Motor Brushes: Powder graphite.

Brike Lining/Shoes for Heavy: Made from amorphous or fine flakes

Graphite (Carbon), Fibers/Nanotubes: Reinforced/antistatic/ conductive plastics/ concreates/ rubbers.

Origin.

Graphite originates by

(1) Regional metamorphism;

(2) Original crystallization from igneous rocks as shown by its occurrence in granite, syenite and basalt;

(3) Contact metamorphism (i.e., as at Calabogie, Ontario, where its occurs with contact metamorphic silicates in limestone adjacent to an igneous intrusion); and

(4) Introduction by hydrothermal solutions, which accounts for vein deposits and as Beverly considers, for deposits in pegmatites and shear zones in schist.


12.3) Talc Formation: Talc, Soapstone , and Pyrophyllite Talc a product of metamorphism, is a hydrous magnesium silicate [Mg3Si4O10(OH)2], which when finely ground, forms the

familiar talcum powder.

There are three main types of talc:

i) Talc steatite: Trade name used to describe pure, soft, massive, compact varieties of talc.

ii) Fibrous talc

iii) Agalite: A special name applied to fibrous talc from New York State. Soapstone is a soft rock composed essentially of talc , with varying amounts of chlorite, micas, serpentine, magnesite,

antigorite and enstatite and perhaps some quartz, magnetite or pyrite. It is a massive, impure talcky rock that can be quarried and sawed into large blocks. Soapstone is typically gray, bluish, green or brown in color, often variegated.

Pyrophyllite {Al2Si4O10(OH)2}; occurs in phyllite and schistose rocks, often associated with kyanite, of which it is an alteration product. It also occurs as hydrothermal deposits. Typical associated minerals include: kyanite, andalusite, topaz, mica and quartz. Pyrophyllite serves some of the same uses as soapstone.

Occurrence : Commercial talc and soapstone depsotis occur in metamorphosed ultrabasic intrusives or dolomitic limestones. They are thus restricted to metamorphic area and are largely confined to the Precambrian. The best quality talc comes from metamorphosed dolomite limestones is generally associated with termolite, actinolite and

related minerals. These deposits are generally lens shaped in beds and reach widths up to 40 m. The important deposits of Ontario, New York, North Carolina, Georgia, California, Bavaria and Austria are of this type (i.e.,

metamorphosed dolomite limestones ). Origin:

Talc is an alteration product of original or secondary mangnesian minerals of rocks. It results from mild hydrothermal metamorphism, perhaps aided by simple dynamic metamorphism but never from

weathering. It is pseudomorphic after minerals such as termolite, actinolite, enstatite, diopside, olivine, serpentine, chlorite, epidote

and mica. It may be formed from any magnesian amphibole or pyroxene acted on by CO2 and H2O according to the reaction:

4MgSiO3 + CO2 + H2O Mg3Si4O10(OH)2 + MgCO3 It thus originates in:

i) regionally metamorphosed limestones, ii) altered ultrabasic igneous rocks ; and iii) contact metamorphic zones adjacent to basic igneous rocks.


http://en.wikipedia.org/wiki/Phyllite

http://en.wikipedia.org/wiki/Schist

http://en.wikipedia.org/wiki/Kyanite

http://en.wikipedia.org/wiki/Hydrothermal

http://en.wikipedia.org/wiki/Andalusite

http://en.wikipedia.org/wiki/Topaz

http://en.wikipedia.org/wiki/Mica

http://en.wikipedia.org/wiki/Quartz

Talc

Mg3Si4O10(OH)2

Hardness 1 (softest mineral)

S.G. 2.58 - 2.83

Color Colourless, white, pale green;

bright emrald-green to dark green,

brown, gray; Greasy feel


http://www.mineralminers.com/images/talc/mins/talm104.jpg

http://z.about.com/d/geology/1/0/v/Q/1/talc500.jpg

Uses Talc is used in the production of ceramics (the main domestic use),

paint, as a filler in paper manufacture (for improving several paper

qualities and in recycling processes), plastics (as a functional filler,

providing rigidity to the plastic), paint and coatings, roofing, rubber,

food, electric cable, pharmaceuticals, cosmetics (talcum powder),

flooring, caulking, and agricultural applications.

Thus, talc is a part of everyday life.

Talc is used in baby powder, an astringent powder used for

preventing rashes on the area covered by a diaper. It is also often

used in basketball to keep a player's hands dry. Most tailor's

chalk, or French chalk, is talc, as is the chalk often used for

welding or metalworking.

Talc is also used as food additive or in pharmaceutical products

as a glidant. In medicine talc is used as a pleurodesis agent to

prevent recurrent pleural effusion or pneumothorax.

Talc is widely used in the ceramics industry in both bodies and

glazes. In low-fire artware bodies it imparts whiteness and

increases thermal expansion to resist crazing. In stonewares,

small percentages of talc are used to flux the body and therefore

improve strength and vitrification. It is a source of MgO flux in high

temperature glazes (to control melting temperature). It is also

employed as a matting agent in earthenware glazes and can be

used to produce magnesia mattes at high temperatures.

Talc is used as a filler, coating, pigment, dusting agent and extender in plastics, ceramics, paint, paper, cosmetics, roofing, rubber and many other products.

Data from the United States Geological Survey

6 November

2014


Pyrophyllite

Al2Si4O10(OH)2

Same thing as Talc with Al instead of Mg

Hardness 1 - 2

S.G. 2.65 - 2.9

Color White, gray, pale blue, pale green,

pale yellow, brownish green

6 November

2014


http://www.mindat.org/photo-60228.html

119

12.4) Ornamental Metamorphic stones Formed by Contact / regional and Metasomatic processes

e.g., Marble, Quartzite, and Serpentinite

Marble and quartzite may be either regional or contact metamorphic.

Marble may also involve metasomatism.

Serpentinite is formed by metasomatic alteration of ultramafic-mafic rocks.


Use of Marbles and Serpentinite Marble and Serpentinite are used as a decorative stone, and the

presence of cavities is often undesirable. For decorative purposes, the cavities may be filled with epoxy

colored to match the background color of the marble. Use of Quartzites

Quartzite is highly resistant to physical and chemical weathering, so it does well in applications like this Rip-rap.

120

12.4.1) Marble Marble is usually the product of metamorphism of limestone or dolomitic limestone. White marble is often dolomitic limestone. Limestones often contain silicate impurities, and the impurities may be converted to minute

crystals of sericite, chlorite, …..etc These crystals may impart a slightly silky luster to the marble, similar to the process that occurs

during the formation of phyllite.

Metamorphic Grade of Marble

Marbles range in grade from slates to schists.

Foliation may be visible in hand specimen:

Foliation may be due to plastic flow during metamorphosis, or

Foliation may be relict sedimentary.

Naming Marble

• Marbles may be named for their color (for example: pink marble, black marble, or white marble).

• Marble may also be named for accessory minerals such as brucite

(Mg(OH)2), grunerite, ….etc


121

Relict sedimentary bedding in marble

Nonfoliated pink Marble

• Marble, CN

• The photo shows strongly twinned

and highly cleaved calcite

Brecciated Marble with Angular

fragments in carbonate matrix

Close up of brucite (Mg(OH)2)


122

Cavities in Marble

The metamorphic process often releases large quantities of CO2.

This gas escapes though the marble and may lead large fractures and cavities in

the rock, in a manner similar to the formation of vesicular basalt.

Mineralogy of Marble

Common non-carbonate minerals in marble include: tremolite, actinolite, diopside,

epidote, phlogopite, scapolite, and serpentine

Epidote (along with albite) occur in lower grade marbles

Sphene, apatite, and scapolite are present in amphibolite facies marbles.

High-Grade Marble Mineralogy

Hornblende, plagioclase, and diopside are common; together with some mica in

the higher grade metamorphism

Under higher grade conditions, dolomite will disappear. Dolomite decomposes to

yield periclase (MgO) or brucite (Mg(OH)2).

Dolomite present in high-grade metamorphics is probably due to retrogressive

metamorphism.

Using:

Marble is used as a decorative stone, and the presence of cavities is often undesirable.

For decorative purposes, the cavities may be filled with epoxy colored to match the background color of the marble.


12.4.2) Quartzite • Quartzites are often the metamorphic product of quartz sandstones • During metamorphism, the quartz grains become interlocking due to

compression and recrystallization. • If shearing forces are large enough, the quartz grains elongate and

interlocking grain boundaries granulate. • The granulation of the boundaries can only be seen in thin section. • In highly sheared quartzites, the quartz grains become lenticular.

• Sioux Quartzite, South Dakota

• Nonfoliated


124

12.4.3) Serpentinite

• Serpentinite marble; Nonfoliated

• Serpentinite from California Mother Lode country, in the Sierra Nevadas

• Metallic mineral appears to be pyrite

Product of metasomatic alteration of ultramafic igneous rocks.

Serpentine minerals are usually pseudomorphous after the minerals they replace.

Serpentines replacing olivine even retain the irregular curving fractures typical of olivine.

The fractures may fill with very fine-grained magnetite produced during the serpentinization process.

Resulting structures are unusual, possibly due to volume expansion during metasomatism.

Slickensides are sometimes seen on serpentinites


Serpentine are hydrous magnesium iron phyllosilicates ((Mg, Fe)3Si2O5(OH)4), chrysotile and picrolite and are of the same composition as serpentine.

Magnesite, in minute grains, inevitably accompanies the serpentine minerals - magnesite is a product of the metasomatic alteration

Other minerals found in serpentinites include tremolite, talc, and anthophyllite, usually as fibers or prisms on the borders of former olivine crystals.

Serpentinite Mineralogy

non-metallic mineral deposits

Education

ore present

minerals metals

high grade ore

occurrence of minerals

minerallow grade ore

useful metallic minerals

mineral of value

commercial mineral deposits