Descriptive Mineralogy Native Elements: Pure elements that occur as minerals.

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 Elements

Native 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

Iron-Nickel Phase Diagram

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

Skaergaard: Layered Gabbroic Intrusion

Skaergaard: Layered Gabbroic Intrusion

Skaergaard: Layered Gabbroic Intrusion

Native 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

Hydrothermal Gold

Hydrothermal 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

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

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

Native Elements