amphibole


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amphibole

(ăm`fəbōl'), any of a group of widely distributed rock-forming minerals, magnesium-iron silicates, often with traces of calcium, aluminum, sodium, titanium, and other elements. The amphibole minerals are closely related in crystal structure, but they crystallize in two different systems, orthorhombic and monoclinic; their close structural relationship is reflected in uniform prism angles of about 56° and 124° and in good cleavages parallel to these prisms. They are commonly green to black, but may be colorless, white, yellow, blue, or brown. The amphibole minerals are found both in igneous and metamorphic rocks. The commonest form is hornblende; other species include anthophyllite, cummingtonite, tremolite, actinolite, riebeckite, and glaucophane. A variety of jade, called nephrite, consists of actinolite in a finely fibrous form.

amphibole

[′am·fə‚bōl]
(mineralogy)
Any of a group of rock-forming, ferromagnesian silicate minerals commonly found in igneous and metamorphic rocks; includes hornblende, anthophyllite, tremolite, and actinolite (asbestos minerals).
References in periodicals archive ?
The best model for understanding asbestos-related fibrogenicity and mesothelial carcinogenicity is the very slow clearance of long, thin biopersistent fibers, of which commercial amphibole asbestos (amosite and crocidolite), erionite, and refractory ceramic fibers are excellent examples, from respiratory compartments.
Epidemiological studies have shown a dose-dependent correlation between Libby amphibole (LA) exposure and the incidences of asbestos-induced diseases, including asbestosis, lung cancer, and mesothelioma (Moolgavkar et al.
In calc-alkaline intrusives, the Al content in calcic amphibole in the presence of an appropriated buffer assemblage can be used to determine pressure of crystallization because of a linear relationship between crystallization pressure and Al content.
The eastern dyke is alkalic, and contains pseudomorphs of olivine phenocrysts in a fine-grained groundmass of plagioclase, brown amphibole, and pyroxene.
Most rocks under the microscope are medium-grained hypidiomorphic to allotriomorphic subequigranular and composed of plagioclase hornblendic amphibole opaque iron oxide quartz and in some biotite titanite and rare perthite.
The rhyolite sheets are sparsely porphyritic, at places banded, and composed of perthite, quartz, albite, sodic amphibole, aegirine-augite, opaque oxide and titanite.
The critique takes issue with the number of asbestos bodies required for a pathologic diagnosis of asbestosis, noting that chrysotile does not form asbestos bodies as well as the amphiboles.
Barker's study revealed three main rock types within what he interpreted to be a composite pluton: (1) fine-grained, leucocratic syenite that contains limited amounts of Na-rich pyroxene (aegirineaugite) and amphibole (riebeckite-arfvedsonite) with no nepheline or quartz; (2) medium- to coarse- grained, magnetite-bearing biotite syenite that similarly contains no nepheline or quartz; and (3) coarse-grained, foliated, biotite nepheline syenite that includes the "type variety" of litchfieldite described by Bayley (1892) and the rock type that is found in most petrologic collections (shown in Figure 2).
Collector's Guide to the Amphibole Group covers an important, beautiful set of crystals--the amphiboles--and organizes them in such a way that mineral collectors will understand their properties and structural features.
IMA report--Nomenclature of the amphibole super group.