Rhodium is one of the rarest precious metals on Earth. It is far rarer than gold or platinum, which is why it is so expensive.

It was discovered in 1803 by William Hyde Wollaston, the same scientist who also discovered palladium.

Its name comes from the Greek word “rhodon,” meaning “rose.” This refers to the rose-colored salts formed by rhodium compounds.

Rhodium’s chemical symbol is Rh, and it belongs to the platinum group metals (PGMs).

Its atomic number is 45, meaning it has 45 protons in its nucleus.

Rhodium is extremely reflective. It reflects more light than tarnished silver or clean platinum and has a bright silvery-white appearance. That is why it is popular in jewelry plating.

Rhodium is very hard and durable, harder than gold and platinum.

It resists corrosion almost completely. Even acids barely affect it.

Its melting point is about 1,964°C (3,567°F), which is hotter than molten lava.

Rhodium is dense, but not the densest metal. Osmium and iridium are heavier.

Rhodium has been the most expensive precious metal at times, surpassing gold, platinum, and even palladium.

Its price is extremely volatile. It can rise or crash faster than most metals.

In 2021, rhodium reached over $29,000 per ounce, more than ten times the price of gold at the time.

There are no major rhodium mines. It is usually extracted as a byproduct of platinum mining.

South Africa produces about 80–90% of the world’s rhodium, which makes the global supply vulnerable to disruptions.

Recycling catalytic converters is a major source of rhodium. Old cars are essentially tiny rhodium mines.

Most rhodium is used in catalytic converters. It reduces harmful car exhaust emissions and helps convert nitrogen oxides into less harmful gases, making it critical for environmental protection.

Rhodium is used in electronics, especially for contacts, because it does not corrode.

It is also used in mirrors and optical instruments because of its high reflectivity.

Rhodium alloys strengthen platinum and palladium, making them useful in high-temperature applications.

It is used in thermocouples, devices that measure extreme temperatures.

White gold jewelry is often rhodium-plated, which gives it a bright white shine.

Rhodium plating prevents tarnish, especially on silver jewelry.

Black rhodium exists and is used for edgy, modern jewelry designs.

Rhodium plating wears off over time, which is why jewelry sometimes needs re-plating.

Rhodium is hypoallergenic, making it a good option for people sensitive to nickel.