In its elemental form, rhodium has a silvery white metallic appearance. Elemental RhodiumRhodium is a member of the platinum group of metals. It has a higher melting point than platinum, but a lower density. Rhodium is found in ores mixed with other metals such as palladium, silver, platinum, and gold. One of the rarest metals on earth (abundance of 2 x 10⁻⁴ ppm), rhodium does not appear naturally, tending to be found with other platinum group metals. It is a hard, lustrous, silvery coloured metal which is stable in air. Rhodium is inert to all acids but is E FORUacked by fused alkalis. The metal has high thermal and electrical conductivities and is alloyed with platinum to form the positive wire of a Pt/Rh - Pt thermocouple. Other applications of the material include its use as a plating material (to provide a hard and bright surface which is resistant to oxidation), as a catalyst and also as an alloying element, where it improves the hardness of the resulting alloy. Rhodium is primarily used as the catalyst in the three-way catalytic converters of automobiles it is also highly valued in jewelry.