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SILICATE VS. NON-SILICATECLASSIFICATION OF MINERALS

ALL MINERALS ON EARTH FALL INTO ONE OF THESE CLASSIFICATIONS

TWO MAIN DIVISIONS OF MINERALS(SILICATE AND NON-SILICATE)

SILICATES (95 % OF EARTH’S CRUST)

• Contain silicon (Si) and oxygen (O)

• Silicate Types:

• Quartz (SiO2)

• Feldspar

• Orthoclase Feldspar (KAlSi3O8)

• Plagioclase Feldspar (NaAlSi3O8 CaAl2Si2O8)

• Ferromagnesian Minerals

• Hornblende (Ca2Fe5Si8O22F2)

• Olivine Fe2SiO4

• Muscovite (KAl2(AlSi3O10)F2)

• Biotite (KMg3AlSi3O10(OH)2)

NON-SILICATES (5% OF EARTH’S CRUST)

• DO NOT CONTAIN SILICON!!!• Carbonates – contain carbonate (CO3)

• Calcite (CaCO3)• Dolomite (CaMg(CO3)2)

• Sulfates – contain sulfate (SO4)• Gypsum (CaSO4)

• Halides – contain (Cl, F with Na, K, Ca)• Halite (NaCl)• Fluorite (CaF2)

• Oxides – contain oxygen (O) and NOT silicon (Si)• Hematite (Fe2O3)• Magnetite (Fe3O4)

• Native Elements – uncombined with other elements• Silver (Ag)• Copper (Cu)

• Sulfides – contain sulfur (S)• Galena (PbS)• Pyrite (FeS2)

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SILICA CONTENT AND MINERAL PROPERTIES

SILICA-RICH MINERALS

• Melt at lower temperatures

• Last to crystallize from cooling magma

• More resistance to chemical weathering

SILICA-POOR MINERALS

• Melt at higher temperatures

• Tend to crystallize earlier in cooling magma

• Less resistance to chemical weathering

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silica-rich feldspar silica-poor olivine

USING CRYSTALLINE STRUCTURE TO IDENTIFY MINERALS

• Minerals have an organized distribution of atoms.

• Crystals are an outward display of internal atomic geometry.

• Bond strength affects the minerals resistance to breakdown.

• Basic building block of silicates is the SiO4

tetrahedron.

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TYPES OF SILICATE CRYSTALS AND CHAINS

• ALL SILICATES ARE BUILT WITH THE

SiO4 TETRAHEDRON.

• Tetrahedron Variations1. Independent tetrahedron

family- Olivine

2. Single-chain tetrahedral family (Share 2 oxygen) Ex. Pyroxenes.

3. Double-chain tetrahedral family (2-3 oxygen shared) Ex. Hornblende

4. Sheet tetrahedral family (3 shared Oxygen)Ex. Micas

5. Network family(all 4 Oxygen shared) very strong bondsEx. Quartz

CRYSTAL STRUCTURES OF NON-SILICATE MINERALS

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Crystal FormSome minerals that grow without being impeded by their environment

develop characteristic crystal shapes or crystal form that represents the

symmetry of the crystal structure. Crystal form can be a diagnostic

property for some minerals.

Quartz has an internal structure

that has a 6-sided (hexagonal)

symmetry. As a result, quartz

crystals commonly are 6-sided.

Halite has an internal structure that

has a cubic (4-sided) symmetry. As

a result, halite crystals commonly

are cube shaped.