Minerals Review

Every mineral… Inorganic Naturally occurring Crystal structure Consistent chemical composition

2 Kinds of Minerals Silicates: contain silicon (Si) and oxygen (O) Nonsilicates: do not contain Si and O together

Silicates Examples: Quartz (SiO2) Serpentine (Mg3Si2O5(OH)4) Muscovite (KAl2(AlSi3O10)(F,OH)2) Make up over 90% of Earth’s crust Arranged as silicon-oxygen tetrahedron

Types of Quartz (not the complete list) Quartz (milky) Quartz (rose) Quartz (smokey) Quartz, agate Quartz, amethyst Quartz, jasper

Classes of Nonsilicates Iron ores Contain iron (Fe) Example: magnetite (Fe3O4)

Classes of Nonsilicates… Oxides Contain oxygen (O) Example: corundum (Al2O3)

Classes of Nonsilicates… Sulfides Contain sulfur (S) Example: Pyrite (FeS2)

Classes of Nonsilicates… Carbonates Contain carbonate (CO3) Example: Calcite (CaCO3)

Classes of Nonsilicates… Micas “sheet silicates” that exhibit basal cleavage Examples: Muscovite and Biotite

Classes of Nonsilicates… Mafic/Ultramafic Minerals or rocks containing a large amount of iron (Fe) and/or magnesium (Mg) Examples: Olivine ((Mg, Fe)2SiO4) Serpentine (Mg3Si2O5(OH)4)

Classes of Nonsilicates… Phosphates Contain phosphate (PO4) Example: apatite (Ca5(PO4)3(F,Cl,OH))

Classes of Nonsilicates… Sulfates Contain sulfate (SO4) Example: Gypsum (CaSO4·2H2O)

Classes of Nonsilicates… Native elements Minerals that are a single element Examples: Sulfur (S) Graphite and diamond (C) Gold (Au)

Classes of Nonsilicates… Halides Contain one or more halogens, such as fluorine (F), chlorine (Cl), and bromine (Br) Examples: Halite (NaCl) Fluorite (CaF2)

Mineral Properties Color Streak Fracture Cleavage Hardness Luster

Color Not a good identifier One exception is sulfur

Streak Powdered form of the mineral Can be used to distinguish gold and pyrite

Fracture When the mineral breaks unevenly Quartz has fracture

Cleavage When the mineral breaks into smooth, flat planes Types:

Hardness Scratch test

Luster The way a mineral reflects light Types:

Specific Gravity

Specific Gravity… The higher the specific gravity, the higher the density of the mineral

Fluorite Fluorescence – glows under a UV light

Quartz Hardness of 7 Used to make glass Many varieties Amethyst Rose Quartz

Muscovite Basal cleavage Used to make computer chips

Biotite Basal cleavage Used in tiles Found in granite

Olivine Also called peridot, August’s birthstone A mafic mineral (melts at very high temperatures)

Serpentine A mafic mineral Releases water under high heat and pressure Can cause rock to melt at lower temperatures in subduction zones

Pyrite “fool’s gold” Used for explosives and fertilizer

Corundum Hardness of 9

Magnetite Naturally magnetic An iron ore

Sulfur Characteristic bright yellow color Rotten egg or match smell

Halite Salt rock

Gypsum Used for drywall

Galena High density Metallic luster

Graphite Used in pencils Greasy feel Elemental carbon (C)

Hematite An iron ore Red streak

Chalcopyrite Softer and darker in color than pyrite Dark green streak

Talc Hardness of 1 Used in make-up

Calcite Main mineral in limestone Effervescent – bubbles in acid Caves form in calcite

Malachite Found in association with calcite A carbonate Green color

Dolomite Found in association with calcite A carbonate Less effervescent than calcite