The pyroxenes are a family of iron-magnesium silicate minerals that are important in igneous and metamorphic rocks, particularly those with a more mafic (iron-magnesium rich) composition formed at higher pressures and temperatures. Pyroxene minerals include aegirine, augite, diopside, hedenbergite, enstatite, jadeite and spodumene.
Pronunciation: PEERoxine (accent on capitalized syllable)
Color: commonly black to dark green or dark brown
Diaphaneity: translucent, but generally appears to be opaque in hand specimen
Specific gravity: 3.4
Cleavage/fracture: 2 directions at approximately right angles
Other distinguishing properties: The pyroxenes may be mistaken for the amphiboles; however, the two cleavages in amphiboles are at oblique angles of around 60° - 120° and amphiboles (i.e., hornblendes) commonly appear to be rectangular or elongate crystals while pyroxenes (e.g., augite) are more stubby and equi-dimensional.
Klein, C., and Hurlbut, C.S., Jr., 1999, Manual of Mineralogy (after James D. Dana) [21st edition, revised]: New York, John Wiley & Sons, 682 p.
Los Angeles County Museum of Natural History, The Photo Atlas of Minerals: nhm.org/pam/
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