It’s commonly believed that gold is one of the rarest and most expensive precious metals – but while it does rank pretty high comparatively, there is one metal that has it beat hands down both for price and rarity.
The monetary worth of different metals is inconsistent, differing slightly depending on demand and access. Due to the versatility of gold, its conductivity, durability, and good looks place it firmly in the top five most expensive metals. Gold prices stand at over $1,850 per ounce at the time of publication – impressive, but nothing compared to rhodium.
Currently the most expensive precious metal and one of the rarest, the price per ounce of rhodium stands at $10,300 at the time of publication. So, what makes it so expensive?
Rhodium doesn’t easily react to oxygen, making it a noble metal and meaning it’s a perfect catalyst, resistant to both corrosion and oxidation. Its overall hardiness and high melting point of 1,964 degrees Celsius (3,567 degrees Fahrenheit) land it among the platinum group metals alongside platinum, palladium, osmium, iridium, and ruthenium.
Its ability to withstand water and air temperatures of up to 600 degrees Celsius (1,112 degrees Fahrenheit), and remaining insoluble in most acids, makes rhodium highly versatile for use in cars, aircraft, electrical contacts, and high-temperature thermocouple and resistance wires.
As the rarest of the platinum group metals, rhodium occurs at roughly 0.000037 parts per million in the Earth’s crust, while gold is found at an abundance of around 0.0013 parts per million, according to the Royal Society of Chemistry. Produced mainly in South Africa and Russia, rhodium can come as a by-product of refining copper and nickel ores, which contain up to 0.1 percent of the precious metal. Around 16 tonnes of rhodium are produced yearly, with an estimated reserve of 3,000 tonnes.
Rhodium’s discovery came in 1803 by William Hyde Wollaston, an English chemist, who extracted the element from a piece of platinum ore from South America. The find came shortly after Wollaston discovered another platinum group metal, palladium.
Generally found along with deposits of platinum, the rhodium was obtained from Wollaston’s sample by removing the platinum and palladium, leaving behind a dark red powder that was treated with hydrogen gas to reveal the precious metal Rhodium.
While the solid metal shines a bright, reflective silver-white color, rhodium gets its name from the Greek “rhodon” meaning rose. Its name refers to the red color of the metal’s salts.
Despite its rarity and beauty, statistics from 2019 show almost 90 percent of rhodium demand was from the auto-catalyst sector in the production of catalytic converters, an arguably unceremonious use for one of Earth’s rarest precious metals.