What is gold in jewellery?
By Jared James · Last updated 21 May 2026
Definition
Gold is a naturally occurring precious metal, warm yellow in its pure state, prized for thousands of years for its beauty, rarity and the fact that it does not tarnish or corrode. In jewellery it is almost always alloyed with other metals to make it hard enough for daily wear, with purity measured in carats: 24ct is pure gold, 18ct is 75% gold, and 9ct is 37.5% gold and the minimum legal standard in Australia. Alloying also creates the different gold colours including yellow, white, rose and green gold.
Frequently asked questions
- What is the difference between gold carats?
- Carat measures how much pure gold is in the alloy. 24ct is 99.9% pure but too soft to wear, 18ct is 75% gold with a rich warm colour, and 9ct is 37.5% gold, harder and more affordable. Australia uses 9ct as its minimum standard.
- Why does gold come in different colours?
- The alloy metals create the colour. Yellow gold uses copper and silver, rose gold is given its blush by a higher copper content, and white gold is made with palladium or silver and usually rhodium-plated. Green gold uses a high silver content. All start with the same pure yellow metal.
- How do I know if gold jewellery is real?
- Look for a hallmark or purity stamp: 750 or 18ct for 18-carat gold, 585 for 14ct, and 375 for 9ct. In Australia hallmarks are not legally required but are standard practice among reputable jewellers.
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