Diagnostic Features
Hardness: 5-6
Streak: White to none
Luster: Nonmetallic
Specific Gravity: 3.3-3.5
Cleavage: Present in two directions,
perpendicular to one another.
Fracture: Rounded
Other: Usually occurs as grains in
mafic and ultramafic igneous
rocks. Grains are usually lathlike
and prismatic.
Identification Tips
1. Augite (and other pyroxene group minerals) principally occur as rod-like crystals in mafic and ultramafic plutonic igneous rock and their volcanic equivalents.
2. The mutually perpendicular cleavage planes and dark, nonmetallic luster are typical of most pyroxene minerals.
3. Complete (euhedral) single crystals usually occur as phenocrysts in porphyritic igneous rocks.
