Crystals are prismatic or acicular. Bismuthinite also occurs in massive, fibrous, or foliated habits. The color is lead gray to silvery white, and the streak is lead gray. It is opaque, with a metallic luster.
FORMATION Forms in high-temperature hydrothermal veins and in granitic rocks. It occurs with native bismuth and various sulfides.
TESTS It is soluble in nitric acid, leaving flaky particles of sulfur on the surface.
Group: SULFIDES
Composition: Bi₂S₃
Hardness: 2
SG: 6.78
Cleavage: Perfect
Fracture: Uneven
