Gold in the purest type is not adequately long-lasting, so it needs to be mixed with an alloy to make it more durable. Pure gold refer to 24-karat gold. No jewelergoldsmith can declare to give you 24k jewelry as it's practically not possible to craft such pure form of gold into jewelry and ornaments. So it is mandatory to mix gold with some other metal copper, silver, nickel, or zinc and then mould it into desirable designs.