SILVER (כֶּ֫סֶף, H4084; Gr. ἀργύριον, G736), one of the precious metals. It is white in color, ductile and so malleable that it can be beaten into leaves as thin as 0.00025 mm. Silver has a density of 10.5 and melts at 961oC. It forms alloys with other metallic elements, including gold, copper, nickel and zinc with 10-15% silver commonly present in native gold. Electrum, which was used for many early coins, is the natural alloy of gold with 15-45% silver; it was called asem in ancient Egypt. The crystal structure of silver, like gold (q.v.) and copper (q.v.) is a facecentered cubic lattice. The cell dimensions of the basic cubic units of four atoms of silver and of gold are almost identical and because of this silver substitutes for gold, and vice versa, right up to 100%.