amphibole

n. (Mineralogy) any of several varieties of common ferromagnesian silicate minerals (such as hornblende and asbestos)

For the logical fallacy, see Amphibology. Amphibole defines an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain SiO4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. In chemical composition and general characteristics they are similar to the pyroxenes. The chief differences between amphiboles and pyroxenes are that (i) they contain essential hydroxyl (OH) or halogene (F, Cl) and (ii) the basic structure is a double chain of tetrahedra (as opposed to the single chain structure of pyroxene). Most apparent, in hand specimens, is that amphiboles form oblique cleavage planes (at around 120 degrees), whereas pyroxenes have cleavage angles of approximately 90 degrees. Amphiboles are also specifically less dense than the corresponding pyroxenes. In optical characteristics, many amphiboles are distinguished by their stronger pleochroism and by the smaller angle of extinction (Z angle c) on the plane of symmetry. Amphiboles are the primary constituent of amphibolites.
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Noun
1. a mineral or mineral variety belonging to the amphibole group
(hypernym) mineral
(hyponym) nephrite
(member-holonym) amphibole group
(substance-holonym) amphibolite

n. amphibole, complex group of minerals

adj. amphibolic, relating to the mineral amphibole

n. amphibole, any of several varieties of common ferromagnesian silicate minerals (such as hornblende and asbestos) (Mineralogy)