Gold is the most common reference to a precious and rare metal. But another metal, less known, is above gold, both more expensive and rarer, ice metal is rhodium. It is a metal in the platinum family, very unreactive to oxygen, and resistant to both corrosion and oxidation, with a melting point of 1,964˚C.
Rhodium is used primarily in exhaust catalysts to reduce pollutant emissions, but also in jewelry manufacturing and data storage. Its scarcity and high demand, especially for automobiles, means that its price is around €277,716/kg in March 2023, compared to around €55,000/kg for gold.
Rhodium was discovered in 1803 by the British chemist William Hyde Wollaston, who was also responsible for the discovery of palladium in 1802. Wollaston discovered rhodium by examining a sample of platinum in which he noticed the presence of a silvery-white metal that did not correspond to the other platinum group metals already known. Because of the pink color of some of the compounds in this rhodium metal, Wollaston called this metal rhodium, after the Greek word rhodon, meaning pink.
The presence of rhodium in its natural state is extremely rare, occurring at only 0.000037 ppm or parts per million in the earth’s crust, whereas gold occurs at about 0.0013 parts per million, according to the Royal Society of Chemistry. South Africa is the main producer of rhodium, the country concentrating most of the metal on the planet, other producing countries being Russia, Canada and the United States. Rhodium is mainly found in underground mines and is extracted mainly as a by-product of platinum, with other platinum group metals also found in the same deposits. Annual rhodium production is 16 tons per year with estimated reserves of 3,000 tons.
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