Rhodium

rhodium

moncheite

kotulskite

merenskyite

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Formula: Rh
Native element, transition metal, platinum group element
Specific gravity: 16.5
Hardness: 3½
Colour: Silver-white
Solubility: not attacked by most acids
Melting point: 1963oC
Boiling point: 3695oC
Abundance in the Earth’s crust: 1 part per billion by mass, 0.1 parts per billion by moles
Abundance in the Solar System: 2 parts per billion by mass, 0.02 parts per billion by moles
Environments

Plutonic igneous environments
Placer deposits

Rhodium occurs in small quantities in ores of metals such as platinum, palladium, nickel, silver and gold. When present in compounds, rhodium exists mostly in the trivalent state, Rh3+ (ChC)

Localities

In Newfoundland, Newfoundland and Labrador, Canada, Samples of spinel lherzolite, harzburgite, dunite and chromitite from ophiolite complexes in several localities were analyzed for the platinum group elements, palladium (0.5 to 77 ppm), platinum (1 to 120 ppm), rhodium (0.5 to 20 ppm), ruthenium (100 to 250 ppm) and iridium (20 to 83 ppm) (CM 22.137-149).

At the Semail Ophiolite, Ash Sharqiyah, Oman, chromitite occurs as pods and lenses in dunite hosts within foliated harzburgite and subordinate lherzolite of mantle origin. The chromitite rocks contain traces of the platinum group minerals, in order of abundance, smallest first, rhodium (6 ppm), palladium, platinum, iridium and ruthenium (135 ppm) (CM 20.537-548).

There are two co-type localities, the Stillwater mine and the Stillwater complex, both in Stillwater county, Montana, USA. At the Stillwater complex, a single grain of rhodium was found in heavy mineral concentrates, associated with platinum, a platinum-iron alloy, gold, moncheite, kotulskite, merenskyite, cooperite, braggite, vysotskite, sperrylite, pyrite, chalcopyrite, pyrrhotite, chromite, magnetite, marcasite, violarite and graphite (HOM, CM 12.399-403).

Rhodium-bearing minerals include:

Sulphides
bowieite
hollingworthite
irarsite
miassite
oberthürite
torryweiserite

Antimonides
fleetite

Arsenides
cherepanovite
rhodarsenide

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