There are six platinum group elements, iridium, osmium, palladium, platinum, rhodium and ruthenium. They often occur together, and are often alloyed with each other.
Specific gravity: 21.4
Hardness: 4 to 4½；
Colour: Silver grey
Solubility: Insoluble in hydrochloric, sulphuric and nitric acid
Most platinum occurs as the native metal in ultramafic rocks,
especially dunite, associated with
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
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