The colours of gold

If you were to go through your jewellery box and take out all of your yellow gold necklaces, rings, bangles and charms and place them side by side, you may be surprised to find they are not exactly alike in colour.

Each by itself looks like yellow gold, so why don’t they all look exactly the same? The answer lies in the fact that 9ct gold contains 9 parts of 24ct gold and 15 parts of other metals by weight.

Gold used to make jewellery is an alloy of different metals. Yellow gold typically contains gold, silver, copper and a touch of zinc. It must be 37.5% gold to be called 9ct, but the other 62.5% can be made up of any mixture of other metals.

As more and more copper (and less silver) is used, the colour of the gold alloy becomes pink, then rose and then red gold. If less copper (and more silver) is used then the gold becomes a brassier shade of yellow gold.

The mixture used in the alloy will also vary between manufacturers, some prefer a bright yellow, others like the slightly warmer tones of pink gold. As fashions change the manufacturers may also change the colour of their alloys to meet the current market desires.