Augite

Color: Pale brown to dark brown or purplish brown, greenish, black

Streak: Grayish green

Luster: Vitreous, resinous to dull

Habit: Crystals short prismatic; massive, granular

Hardness: 5.5 to 6

Specific gravity: 2.70 to 3.40

Cleavage: 3; {110} good; {100} and {010} parting

Tenacity: Brittle

Twinning: Common on {100}, contact, simple, repeated; on {001}, lamellar

Crystal system: Monoclinic

Crystal class: 2/m

Unit cell: a = 9.70 Å, b = 8.84 Å, c = 5.27 Å, b = 106.97°

Synonyms/varieties: Fassite (Fe3+, Al-rich var.), ferrohedenbergite, jeffersonite (Mn, Zn-rich var.), violan (Fe=Mg var.), asteroite (Fe-rich var.)