Why Jewellery Is Not Pure Gold: Alloys Explained

It can come as a surprise that gold jewellery is not pure gold. The 22K bangle or 18K ring you buy is a carefully balanced mix of gold and other metals. That is normal, intended and necessary.

What is an alloy?

An alloy is a mixture of metals. Jewellery gold is alloyed so that it is harder, more durable and can be made in different colours. The gold content is stated by karat: 18K is 75 percent gold, 22K is 91.6 percent gold.

Why not use pure gold?

Pure gold, at 24 karat, is very soft and malleable. It dents, scratches and bends easily. A ring of pure gold would lose its shape quickly, and prongs would not hold a diamond in place. Alloying gold with harder metals solves this.

What metals are mixed in?

• Copper: hardens the gold and adds a warm, reddish tone. More copper gives rose gold.
• Silver: lightens the colour and keeps it workable.
• Zinc: helps with casting and can improve colour balance.
• Palladium or nickel: used in white gold to make it pale.

The exact recipe varies by maker and by the colour wanted.

How the alloy affects colour

The balance of the metals decides the shade. A mix with more silver leans greenish-yellow, more copper leans rose, and white metals produce white gold. You can read more in rose, white and yellow gold: how to choose.

How the alloy affects durability

A higher karat means softer metal. That is why we prefer 18K for stone settings and why 22K is used for plainer, heavier items. See 18K vs 22K gold jewellery.

Does an alloy make jewellery less valuable?

No. Gold jewellery's value is based on its gold content in line with its hallmarked purity. An 18K piece contains 75 percent gold, exactly as marked. If a piece is below the purity it claims, that is a problem, not the alloy itself. This is why hallmarks matter, and how to read them is explained in BIS hallmark marks explained.

Is alloy the cause of skin reactions?

Some people react to certain metals, notably nickel, which is sometimes used in white gold. If you have sensitive skin, ask what is in the alloy. Platinum and palladium are alternatives to discuss. See skin sensitivity and jewellery metals explained.

Alloy and tarnish

Gold itself does not tarnish. The other metals in the alloy can react with substances on the skin or in the air, and in low-karat gold that can show up as slight darkening. Regular cleaning keeps it fresh. See how to clean gold jewellery at home.

What this means when you exchange or sell

When a piece is valued for exchange, the figure that matters is the actual amount of gold in it. A tested 18K piece is counted as 75 percent gold, and the other metals are not counted at the gold rate. That is perfectly fair: you paid for gold at 75 percent purity, and that is what is returned to you in value. The only thing you do not recover is the labour, which is explained in gold making charges.

What you should expect from a jeweller

You should be told the karat, see the hallmark and have the purity and weight on the bill. If you would like to understand your piece better, book a visit, or browse our diamond jewellery to see how purity is listed for each item.