Gold carats explained: 9, 18, 21, 22 and 24 carat
The carat shows the share of pure gold in an alloy, on a scale of 24. It measures neither the weight of a piece nor the quality of its making.
The carat table
24 carat: 99.9% pure gold (fineness 999).
22 carat: 91.6% pure gold (fineness 916).
21 carat: 87.5% pure gold (fineness 875).
18 carat: 75% pure gold (fineness 750).
9 carat: 37.5% pure gold (fineness 375).
Why gold is alloyed
Pure gold is very soft and scratches easily. It is therefore mixed with other metals, such as silver or copper, to make it stronger. The mix also creates the colours: yellow, rose and white gold.
Which carat to choose
18 carat gold is common in jewellery: it combines a high gold content with good strength. 9 carat gold contains half as much pure gold, which makes it cheaper per gram. At equal weight, its gold value is therefore half as much.
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