Natural gold has always been considered appealing due to its beautiful rich colour, its lustre and its malleability. It is also relatively easy to extract from the earth and process compared to other precious metals. The oldest evidence of gold being used in jewellery making comes from Egypt around 4000 BC; the oldest gold objects excavated date to around 4400 BC.
A Byzantine coin known as a Solidus, which can be split into 24 ‘Keratia’, is what gives us our present day purity system. The amount of gold in an alloy is expressed in parts of 24, hence 18ct gold is 18/24 parts gold or 75% pure. Some jewellery may be marked 750 as opposed to 18ct.
The colour of gold is dependent on the different alloys that are added to it. The addition of copper gives a nice warm rose gold; a red gold is produced when lots of copper is added. White gold was traditionally made by blending the gold with zinc and nickel. However, nickel is rarely used nowadays due to the number of people who suffer an allergic reaction to it. Rhodium, a member of the platinum family, is nearly always used to plate white gold. Rhodium gives a lovely mirror-like finish to the gold, however, it will require replating occasionally.
Traditionally, zinc and nickel were blended with the gold to give the white colour. Today, nickel is rarely used because of the amount of people who suffer an allergic reaction to it. White gold is nearly always plated with rhodium, a member of the platinum family. Rhodium gives a mirror-like finish but will need replating from time to time.