Definition of amphibole group
: a group of minerals (as anthophyllite, tremolite, actinolite, and hornblende) with essentially like crystal structures involving a silicate chain [OH(Si4O11)]n and generally containing three groups of metal ions, the large ions being sodium and calcium, the intermediate being chiefly bivalent iron, magnesium, and manganese, and the small ions chiefly silicon with some aluminum and rarely ferric iron, the general formula for the group being A2B5(Si, Al)8O22(OH) 2
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