Electrum

Electrum, a native alloy of gold and silvei containing upwards of one-fifth silver. It is 90 named by Pliny. It occurs in Sutherland with 21 per cent. silver; but more usually, as in Transylvania, the Altai and Colombia, with 36 to 38 per cent. Its colour ranges from brass-yellow to yellowish-white, and its specific gravity varies regularly with the silver percentage from 155 to 12-5. It crystallises in the cubic system, in forms often more sharply defined than those of native gold.