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Descriptive Mineralogy

Native Elements:Pure elements that occur

as minerals

Classification of the Minerals• Non-Silicates

– Native Elements– Halides– Sulfides– Oxides– Hydroxides– Carbonates– Sulfates– Phosphates

• Silicates– Orthosilicates– Sorosilicates– Cyclosilicates– Chain Silicates– Layer Silicates– Tektosilicates

Native ElementsNative Elements: Metals

• Fe, Co, Ni: Meteorites

• Platinum Group: (Ru, Rh, Pd, Os, Ir, Pt): Mafic Igneous Rocks

• Coinage metals: Cu, Ag, Au– Cu, Ag: Supergene Enrichments (Sulfide

Oxidation)

– Au: Low Temperature Hydrothermal, Placer

Native Iron: Meteorites Native Iron: MeteoritesWidmanstätten Pattern

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Iron-Nickel Phase Diagram

FCC

BCC

Platinum Group MetalsRu, Rh, Pd, Os, Ir, Pt

• Strongly siderophile elements• Enriched in Fe meteorites• Found in layered mafic intrusions

– Bushvelt Complex (South Africa)– Stillwater Complex (Montana)– Skaergaard Complex (Greenland)

Bushvelt: Layered Gabbroic Intrusion Bushvelt: Layered Gabbroic Intrusion

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Skaergaard: Layered Gabbroic Intrusion Skaergaard: Layered Gabbroic Intrusion

Skaergaard: Layered Gabbroic IntrusionNative Elements: Cu, Ag, Au• Cu and Ag: Supergene Enrichment

– Oxidation of Cu, Ag sulfides in unsaturated zone

– Precipitation of metal, oxides and carbonates at water table

• Ag and Au: hydrothermal– Native metals and tellurides

• Au: placer – oxidized hydrothermal

Supergene Copper Hydrothermal Silver

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Hydrothermal Gold Hydrothermal Gold

Gold Tellurides

• Calaverite (AuTe2)

• Krennerite (Au3AgTe8)

• Sylvanite (AuAgTe4)

• All weather to TeO2 + native gold

Native Elements: non metals

• Carbon: – Graphite: Metamorphic Rocks– Diamond: Kimberlites

• Sulfur (+Se): – Salt Domes (Sulfate reduction), – Volcanos (H2S oxidation)

• Tellurium (Te) Telluride oxidation

Native Elements: Carbon

• Graphite (Low Pressure)– Metamorphosed Organic-rich sediments

• Diamond (High Pressure >100km)– Kimberlites– Placers from kimberlites

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Native Elements: Diamond Native Elements: Diamond

Kimberley Mine 1875

Native Elements: Sulfur

• Fumaroles (Volcanic hydrothermal vents)– Oxidation of H2S

• Salt dome cap rocks– Sulfate reduction by petroleum

Fumarole Sulfur: Nysseros

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Fumarole Sulfur: Kilauea In the caps of salt domes, gypsum (CaSO4 2H2O) is reduced to native sulfur

Native Elements