An alloy of gold with various other metals, e.g. silver, palladium, copper, nickel, iron, etc., depending on the hardness and colour desired and the intended use,gold being too soft for practicable use alone. All alloys diminish malleability and increase resistance.The purity (fineness) of gold alloy is expressed in carats, 1 carat being 1/24th part by weight. The legal standards for gold alloy in Great Britain, in carats, are 22 (91,66%), 18 (75%), 14 (58,5%),and 9 (37,5%), and these are the only hallmarks employed, even though a slightly higher proportion of gold is used; most gold jewelry is of 14 or 18 carats, but 9 carats for some chains, etc., thatrequire hardness. Different standards are used in other countries.