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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
andrieslombaardite
bowieite
ferrotorryweiserite
hollingworthite
irarsite
miassite
oberthürite
torryweiserite
Selenides
zaykovite
Antimonides
fleetite
Arsenides
cherepanovite
rhodarsenide
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