24k is the purest form of gold, although most jewellery is designed and manufactured in 18k gold because it is considered standard for most of the jewellery items due to its durability. 18k gold means purity of gold in a gold alloy is 18 parts (18/24) and 6 parts of another metal. As the karat of the gold is decreased the ratio of other metal is increased in the jewellery which decreases its value and purity. So you come to know that 24k is the most pure form of gold but you donâ€™t buy 24k gold because gold is a soft metal and it can be damaged easily in its pure form. Therefore it is necessary to mix a metal with gold to form jewellery items such as necklaces, rings, earrings and bracelets.