\Am"phi*bole\ ([a^]m"f[i^]*b[=o]l), n. [Gr.
'amfi`bolos doubtful, equivocal, fr. 'amfiba`llein to throw
round, to doubt: cf. F. amphibole. Ha["u]y so named the genus
from the great variety of color and composition assumed by
the mineral.] (Min.)
A common mineral embracing many varieties varying in color
and in composition. It occurs in monoclinic crystals; also
massive, generally with fibrous or columnar structure. The
color varies from white to gray, green, brown, and black. It
is a silicate of magnesium and calcium, with usually
aluminium and iron. Some common varieties are {tremolite},
{actinolite}, {asbestus}, {edenite}, {hornblende} (the last
name being also used as a general term for the whole
species). Amphibole is a constituent of many crystalline
rocks, as syenite, diorite, most varieties of trachyte, etc.
See {Hornblende}.