Color: black, dark brown, reddish brown, green, or very rarely white
Streak: colorless
Hardness: 2 1/2–4
Specific gravity: 2.7–3.4
Cleavage: perfect basal (pulls apart in thin sheets)
Fracture: uneven
Luster: vitreous
Crystal form: monoclinic
Transparency: transparent to nearly opaque
Forms in both igneous and metamorphic rocks.
For an explanation of the properties (in bold face), click here >>