Crystals are rare, forming as cubes and octahedra, sometimes in parallel bands. The usual habits are as wires, scales, dendrites, and massive. Silver is silver white in color, though it tarnishes on exposure to the atmosphere. It produces a silvery white streak. Silver is opaque, and the luster is metallic.

FORMATION Forms in hydrothermal veins and in the oxidized regions of ore deposits, with other silver minerals, gold, and metallic sulfides. Silver forms 20 to 25 percent of the gold and silver alloy, called electrum.

TESTS Silver is soluble in nitric acid and is fusible. It tarnishes if exposed to the fumes of hydrogen sulfide. It is the best conductor of electricity and heat.

Group: NATIVE ELEMENTS

Composition: Ag

Hardness: 2½–3

SG: 10.50

Cleavage: None

Fracture: Hackly