Gold Jewellery

For jewellers, gold's softness and natural beauty have always been appealing, as well as the fact that it doesn't corrode or tarnish. Pure gold is so soft, in fact, that it's rarely used in jewellery. Instead, it's mixed with another metal to make a stronger gold alloy (mixture of metals). 
The quantity of gold in a given alloy is expressed in carats (ct). Pure gold is 24ct, and 75% gold is 18ct. At lower carat values, the metal can become more durable, but less yellow. So lower carat gold is sometimes plated in high-carat gold to enhance the colour. There's nothing wrong with this, but keep in mind that gold plating will wear off with time, and your jewellery may need to be re-plated. 

When buying gold jewellery, look for the 'hallmark' (the manufacturer's registered trademark), a standard mark telling you the carat value, and a guarantee mark, which shows that a third party has tested and warranted the quality.