Conversations with the Earth

Tom Burbinetburbine@framingham.edu

Quiz on Thursday

• You can bring in your hand-written mineral sheets

• Cation – positively charged ion• Anion – negatively charged ion

• NaCl – Na+ is the cation and Cl- is the anion

Mineral classes that we studied • Silicates – contain silicon and oxygen• Carbonates – contain (CO3)2−

• Sulfates – contain (SO4)2−

• Halites – contain F−, Cl−, Br−, or I− as an anion• Oxides - contain oxygen (O2-) that is bonded to one or more

metal ions• Sulfides - contain sulfur (S2−) as the anion• Native elements

Graphite• C• Used in pencils• Greasy feel• Grey streak• Electrical conductor

Olivine

• (Mg,Fe)2SiO4

• Green, no cleavage• Olivine and high pressure structural

variants make up over 50% of the Earth's upper mantle

Biotite

• K(Mg,Fe)3AlSi3O10(F,OH)2

• Sheets• Dark color

Galena

• PbS• Cubes• Gray streak• Lead ore

Pyrite

• FeS2

• Hardness 6 to 6.5• Gray streak• Can form cubes• Ore for sulfur

Hematite

• Fe2O3

• Reddish streak• Metallic or non-metallic luster

Fluorite

• CaF2

• Hardness of 4• Colorless, purple, green, yellow

Halite

• NaCl• Salt• Cubes• Results from the drying up of

lake beds or seas

Muscovite

• KAl2(AlSi3O10)(F,OH)• Comes in sheets• Clear

Talc

• Mg3Si4O10(OH)2

• In loose form, it is known as talcum powder

• Most tailor's chalk is talc

Amphibole

• Ca2(Mg,Fe,Al)5(Al,Si)8O22(OH)2

• Prisms with cleavage at 56o and 124o

• Fibrous varieties used as fireproof clothing

Calcite

• CaCO3

• Single calcite crystals display an optical property called double refraction

Garnet

• Mg3Al2(SiO4)3

• Hardness of 7• Forms dodecahedrons• Gemstone

Gypsum

• CaSO4·2H2O• Hardness of 2• Colorless, white,

or gray

Dolomite

• CaMg(CO3)2 • Fizzes in dilute HCl

if powdered

Quartz

• SiO2

• second most abundant mineral in the Earth's continental crust

Chalcopyrite

• CuFeS2

• Hardness of 3.5-4• Dark gray streak• source of ignition in early

firearms

Chlorite

• (Mg,Fe)3(Si,Al)4O10 • Very soft• The powder generated by

scratching is green. • Feels oily when rubbed

between the fingers.

Sphalerite

• (Zn,Fe)S• Smells like rotten eggs if

scratched/powdered• Ore of zinc

Plagioclase feldspar

• CaAl2Si2O8

• Has striations

Magnetite

• Fe3O4

• most magnetic of all the naturally occurring minerals on Earth

Augite (pyroxene)

• (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6

• Cleavages at nearly right angles

Potassium feldspar (Orthoclase)

• KAlSi3O8

• Usually pinkish

Kaolinite

• Al2Si2O5(OH)4

• soft, earthy, usually white mineral

• Produced by weathering of feldspars

• main component in porcelain

Any Questions?