AMPHIBOLE

am·phi·bole   (ām'fə-bōl')    n.  Any of a large group of structurally similar hydrated double silicate minerals, such as hornblende, containing various combinations of sodium, calcium, magnesium, iron, and aluminum. [French, from Late Latin amphibolus, ambiguous, from Greek amphibolos, doubtful, from amphiballein, to throw on either side : amphi-, amphi- + ballein, to throw; see gwelə- in Indo-European roots.] am'phi·bol'ic (-bŏl'ĭk) adj.

Main Entry: am·phi·bole
Pronunciation: 'am(p)-f&-"bOl
Function: noun
: any of a group of complex silicate minerals with like crystalstructures that contain calcium, sodium, magnesium, aluminum, and iron ions or a combination of them —see CROCIDOLITE

amphibole   (ām'fə-bōl')  Pronunciation Key  Any of a large group of usually dark minerals composed of a silicate joined to various metals, such as magnesium, iron, calcium or sodium. Amphiboles occur as columnar or fibrous prismatic crystals in igneous and metamorphic rocks. Most are monoclinic, but some are orthorhombic. Hornblende, actinolite and glaucophane are amphiboles. Chemical formula: (Mg,Fe,Ca,Na)2-3(Mg,Fe,Al)5(Si,Al)8O22OH2.