Gold’s versatility, conductivity, durability, and aesthetic appeal firmly establish it among the top five most valuable metals. The current price of gold exceeds $1,850 per ounce – an impressive figure, but one that pales in comparison to rhodium’s value.
At present, rhodium claims the title of the world’s most expensive and rarest metal, commanding a price of $10,300 per ounce.
What makes it so expensive?
Why is rhodium so expensive?
Rhodium belongs to the transition metal series and is chemically unreactive with oxygen, classifying it as a noble metal. This unique property makes it a perfect catalyst, resistant to both corrosion and oxidation. With its exceptional hardness and a melting point of 1,964 degrees Celsius (3,567 degrees Fahrenheit), rhodium shares its position among the platinum group metals, including palladium, osmium, platinum, iridium, and ruthenium.
Rhodium’s remarkable ability to withstand temperatures up to 600 degrees Celsius (1,112 degrees Fahrenheit) and its insolubility in most acids make it an invaluable resource in various industries, including automotive, aviation, electrical components, high-temperature thermocouples, and resistance wires.
In the Earth’s crust, rhodium occurs at a mere 0.000037 parts per million, while gold is relatively abundant at about 0.0013 parts per million, according to the British Royal Society of Chemistry. Rhodium production primarily takes place in South Africa and Russia, often as a byproduct of refining copper and nickel ores containing up to 0.1 percent of this precious metal. Approximately 16 tons of rhodium are produced annually, with an estimated reserve of 3,000 tons.
The discovery of rhodium dates back to 1803, credited to William Hyde Wollaston, an English chemist. Wollaston extracted the element from a piece of platinum ore originating from South America. This breakthrough followed closely after Wollaston’s identification of another group of platinum metals, including palladium.
Due to its typical association with platinum deposits, rhodium was isolated from Wollaston’s sample by removing platinum and palladium, resulting in a dark red powder. Subsequently, hydrogen gas treatment revealed the precious metal – rhodium.
Despite its solid silver-white appearance and reflective qualities, rhodium derived its name from the Greek word “rhodon,” meaning rose. The name alludes to the red color of the metal salts it forms.
Surprisingly, despite its rarity and beauty, statistics from 2019 indicate that nearly 90% of rhodium’s demand comes from the automotive catalyst sector for catalytic converters.
Rhodium finds its primary application in alloys as a hardening agent, commonly added to platinum and palladium. These alloys serve diverse purposes in furnaces, melting reactors, laboratory settings, and beyond. Additional uses for rhodium include jewelry production, electrical contacts in electronic components (owing to its low electrical resistance), serving as a catalyst in industrial chemical reactions (facilitating the production of the rare amino acid L-DOPA through a stereoselective process), and coating optical devices (through an electrolysis process, which imparts impressive strength to rhodium).
Undoubtedly, these applications may seem unusual for one of the Earth’s scarcest precious metals.
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