Pure gold (24 carats) is very soft and so the jewellery or ornaments made from it do not resist much pressure. Even a little pressure can change their shape. Moreover they cannot resist much of wear and tear caused by friction. So, gold is alloyed with other metals like copper and silver to make it hard. 22 carat gold means it contains 22 parts of gold and 2 parts copper or silver in 24 parts by weight of an alloy.
