Metals used in modern British coins

We handle currencies practically daily. We discuss their value, and collectors like us analyze their designs in great detail. But unless the coin is a precious metal, we rarely investigate what metals make up the coin and why they were used. So I thought I would.

Can we use any metal?

Not really. We have to remember that coins are the physical and practical manifestation of money. We handle, store and change them on a regular basis. So coins must have some fundamental properties.

Coins must be safe to the touch.

We cannot have coins that are radioactive or made of material that would be toxic to humans.

The coins must be durable.

We would like the coins to have a long life of 30 years or more. The metal used must be quite strong and not decay due to constant handling by humans or the weather. Coins that would rust quickly are of no use to us. Therefore, the metal must have high wear resistance and anti-corrosion properties.

Coins must be easy to make.

We need to have tens of millions (or more) of coins in circulation. We must be able to use efficient processes to manufacture this number. We use stamping and pressing so the metal needs to be soft enough to use dies to do this.

The value of the metal must be less than the face value of the coin.

If we were to make pennies using gold, they would disappear from the smelters as fast as they were minted and the country would be bankrupt!

It’s not always obvious as you may think, as conditions change over time. Pre-1992 British pennies were 97% copper with 2.5% zinc plus 0.5% tin, an alloy known as bronze. Twenty years later, this meant that there were 1.5 copper pence in every penny.

Therefore, the range of suitable metals is limited and, in most cases, alloys of one or more metals are used.

The metals of coins have changed over the years.

To avoid the penny problem described above, since 1992 the British penny is actually copper clad steel, consisting of 94% steel and only 6% copper.

The United States had a similar problem. Pennies were made of copper (except during the war years when copper was in short supply), but pennies today are copper-coated zinc.

Silver was a popular material for circulation coins from the earliest days. In Britain, prior to 1921, silver coins (such as shillings, guilders, half crowns) were 92.5% pure silver (sterling silver, the rest usually copper). This became 50% silver and by 1947 there was no real silver in the “silver” coins.

Cupronickel (75% copper, 25% nickel) became the popular choice to replace silver. Cupronickel is bright like silver and highly resistant to corrosion in seawater. However, in 2011 the price of copper was enough to switch lower denomination silver coins (5p, 10p) to using nickel-plated steel (94% steel, 6% nickel).

The 50p pieces remain cupronickel (75% copper, 25% nickel), as are the £5 coins (which replaced the 25p krone in 1990). For whatever reason, 20 pence coins are called cupronickel, but they have a different ratio of 84% copper and 16% nickel.

As coins last much longer than notes, the pound note was replaced with a circular pound coin introduced in 1984. To give it a golden color, the alloy was 70% copper, 24.5% zinc, and 5 .5% nickel.

bimetallic coins

Bimetallic coins have been around for some time, but not in the UK. There was a tin penny with a copper stopper in 1692, but for most purposes the £2 coin was the first.

The two pound (£2) coin is a bimetallic coin introduced in 1998 (although the first date back to 1997). The outer circle is nickel-brass (76% copper, 20% zinc, 4% nickel) and the inner ring is cupronickel (75% copper, 25% nickel).

Having different materials for the outer and inner circle means that the outer circle can be harder than the inner circle, giving the coin protection. It also makes the coin more difficult to duplicate, since counterfeiting is a perennial problem with coins in circulation.

Unfortunately, coins are much easier to counterfeit than bills. By 2014, it was estimated that 3% of round pound coins were counterfeit and the Royal Mint redesigned the one pound coin into a 12-sided bimetallic coin with many built-in security features.

The new one pound coin was launched in 2017. The outer ring is gold-colored nickel-brass (76% copper, 20% zinc, and 4% nickel) and the inner ring is a silver-colored nickel-plated alloy . The Royal Mint minted 300 million of them!

Precious metal bars and proof coins

The UK gold coins are basically the gold Sovereign and the gold Britannia and their families.

Years ago, the sovereign was a work currency that was often handled and since gold is a very soft metal, copper was added to make the currency harder and more resistant to wear. The gold sovereign is 22 karat, which is 91.67% gold in the traditional ratio of 11/12 gold, 1/12 copper.

These days bullion coins are only lightly handled and proofs are hardly ever touched so the UK has followed the trend and Britannia gold is minted at 999.9 (99.99%) gold.

Silver Britannias are 999 silver. The Royal Mint also uses platinum for some coins to the 0.9995 standard.

Some silver coins are gold plated. The alloy of gold and silver is called electro.