The amphiboles are a family of silicate minerals. Members of the amphibole family include glaucophane, hornblende, riebeckite, tremolite, anthophyllite and cummingtonite.
Pronunciation: AM•fib•bowl (accent on capitalized syllable)
Color: generally black; also dark green, dark brown
Luster: nonmetallic
Diaphaneity: translucent, but looks opaque in hand specimen
Hardness: scratches glass (5.5 to 6)
Specific gravity: 3-3.4
Cleavage/fracture: 2 good cleavages at angles of ~60/120 degrees
Other distinguishing properties: common mineral in granites, diorites, and other igneous and metamorphic rocks, and is the primary mineral in amphibolites; commonly presents as a roughly rectangular (prismatic) black mineral in hand specimen; oblique cleavage planes distinguish the amphiboles from the pyroxenes, whose cleavages are at ~90 degrees.
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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