Platinum

platinum

chromite

pyroxene

olivine

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Formula: Pt
Native element
There are six platinum group elements, iridium, osmium, palladium, platinum, rhodium and ruthenium. They often occur together, and are often alloyed with each other.
Crystal System: Isometric
Specific gravity: 14 to 19 measured, 21.472 calculated
Hardness: 4 to 4½；
Streak: Grey
Colour: Silver grey
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Environments:

Sedimentary environments
Placer deposits
Hydrothermal environments

Most platinum occurs as the native metal in ultramafic rocks, especially dunite, associated with olivine, chromite, pyroxene and magnetite. It has been mined extensively in placers which are usually close to the platinum-bearing parent rock. It also occurs in quartz veins.

Platinum-bearing minerals include

Alloys - an alloy is a substance that combines more than one metal or mixes a metal with other non-metallic elements
Arsenides - the arsenide anion is As^3-
Antimonides - the antimonide anion is Sb^3-
Sulphides - the sulphide anion is S^2-
Tellurides - the telluride anion is Te^2-
Sulphosalt - A_mB_nX_p: where A is a metal , B usually a semi-metal and X is sulphur, selenium or tellurium
Bismuthides - the bismuthide anion is Bi^3-
Tellurobismuthides - bismuthides where tellurium replaces some bismuth

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