22 karat gold is one of the standards for measuring gold purity. Because gold in its purest form is not very strong and easily breaks, it cannot be used to make gold ornaments. Some impurity is ...

This means that if you buy 18K gold, 18 of the 24 parts will be pure gold and the rest will be a 50:50 mix of copper and silver because the purest gold is too soft to be used in jewellery.