|Composition of Gold Alloys|
Gold jewelry is not pure gold, it is really an alloy, or mixture of metals. The purity or fineness of gold in the jewelry is indicated by its karat number.
24 karat (24K or 24 kt) gold is as pure as gold for jewelry gets. 24K gold is also called fine gold and it is greater than 99.7% pure gold. Proof gold is even finer, with over 99.95% purity, but it is only used for standardization purposes and is not available for jewelry.
Gold can form alloys with most metals.
However, other metals can be added to make colored gold.
Pure gold is a deep yellow colour (an orange shade of yellow) and is soft and very malleable. The coloured carat gold alloys range in gold content from 8 to 22 carats (33.3% - 91.6% gold) and can be obtained in a range of colour shades: green (actually a green shade of yellow), pale yellow, yellow, deep yellow, pink/rose and red. There are also white golds and even unusual coloured golds such as 'purple gold'. They all have different mechanical properties such as strength, hardness and malleability (ductility) and some alloys can be heat treated to maximise strength and hardness. There are gold alloys that are optimised for different manufacturing routes such as lost wax (investment) casting and stamping.
White gold alloy compositions
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