Platinum group metals

Platinum group metals, or PGMs, is a name for collection of six elements. The platinum group metals consist of six noble metals - meaning they are resistant to corrosion.

The platinum group metals are: iridium, osmium, palladium, platinum, rhodium and ruthenium. All metals in the platinum group are 'silvery' coloured, but osmium has a slight blue tint. In chemistry, the other generally accepted noble metals (not in the platinum group) are gold and silver.

The six platinum group metals share many characteristics and are usually discovered together in the Earth's crust amongst nickel sulfide or copper minerals. The majority of the group are currently produced from copper and nickel deposits. The largest new deposits are now being mined in Siberia, Russia, and Bushveld, South Africa.

After mining, all the platinum group metals require costly and complex extraction processing. This involves smelting, followed by hydrometallurgical refining. Because of these costly processes and their extreme geological rarity, up to a quarter of platinum group metals in use are obtained from recycling rather than mining.

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Platinum group metals uses

As noble metals, all the platinum group are corrosion-resistant and therefore used in medical applications. Iridium has the highest resistance. All are excellent electrical conductors and used extensively in electronics. Osmium has the highest conductivity and is often alloyed with other metals in digital equipment.

The largest use of platinum group metals is as catalysts. They are used extensively in chemical processing and fuel cells. By far the largest consumer is the automotive industry, for catalytic converters.

All the platinum group metals are traded on the commodities markets. Platinum and palladium bars and coins are readily available and offer investors an alternative to gold and silver bullion. The options are more limited but they can add further diversity to precious metal investment.

As with gold and silver bullion, platinum and palladium bars and coins are a safe haven investment. The physical metals are free of counterparty risk from actions by governments and banks. For UK tax purposes they are treated very much like silver bullion. That means unlike gold bars they are subject to VAT, whilst legal tender coins remain exempt from Capital Gains Tax.

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What are platinum group metals?

The platinum group metals are listed below with key information.

Platinum

Chemical symbol: Pt

Named from the Spanish ‘platina’ meaning silver

Platinum has a high melting point. Mostly alloyed with other metals to resist scratching. It is used in
jewellery and in industry because of its catalytic properties.

Palladium

Chemical symbol: Pd

Named after the asteroid Pallas

Palladium has a high melting point. Alloyed with other metals it is used in jewellery, in industry as a
catalyst, and in chemical processing to absorb hydrogen.

Rhodium

Chemical symbol: Rh

Named after the rose colour of its salts

Rhodium has a high melting point. It is used in jewellery, in industry as a catalyst,
in glass-making, and for electroplating.

Iridium

Chemical symbol: Ir

Named after Iris, goddess of the rainbow

Iridium is the rarest platinum group metal and the most resistant to corrosion. Its extremely
high resistance to oxidation makes it particularly suitable in medical applications.

Ruthenium

Chemical symbol: Ru

Named after the Russian nation

Like others in the group it has a high melting point. It is extremely hard but brittle, with an unusual
hexagonal formation of its atomic structure. Because of the brittle nature it is generally alloyed, and
rarely used in a pure state.

Osmium

Chemical symbol: Os

Named from Greek word for 'odour.'

Osmium, with its subtle blue tint, has the highest melting point of the group. It is also the
joint hardest and densest in the group. It is mainly alloyed and rarely used in a pure state.

It is an extremely good conductor and catalyst, and as such is used in fuel cells, and in
forensic science for the detection of fingerprints.

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Platinum group metal identification

All of the platinum group metals were known to early civilisations, though true identification would take many more years to achieve. Platinum is present in the Casket of Thebes which dates back to 700 BC. In addition to gold and silver, the cask is decorated with hieroglyphics in an alloy of the platinum group metals. Centuries before the Spanish conquest, the indigenous peoples of South America produced intricate jewellery containing platinum group metals, mixed in with other precious metals.

Despite such artefacts, ancient metal workers lacked the complex refinery techniques required to produce pure platinum group metals. It was not until the late 18th century that pure PGMs began to be refined. The French scientist, P.F. Chabaneau, was first to refine pure platinum in 1789. English chemist William Wollaston discovered palladium in 1802 and rhodium in the following year.

In 1803 another English chemist, Smithson Tennant, identified iridium and osmium. Finally, in 1844, a Russian chemist - Karl Karlovich Klaus - discovered ruthenium, the last metal of the platinum group.

The German refiners Heraeus made their name by inventing a way to superheat furnaces in order to smelt platinum in larger quantities; a move which led to rapid growth of what was a small apothecary in rural Germany, and led to it being one of the most famous international precious metal refiners in the world.