Readers interested in this complex group of minerals should refer to that article and to the original paper by leake et al. Among igneous rocks they are found in all the major groups ranging from ultrabasic to acid and alkaline types, but are particularly common constituents of the intermediate members of the calcalkali series. Their presence in a rock indicate a high temperature of crystallization with a lack of water. The amphibole group is composed of minerals of the general formula the crystal structure of amphibole. Members of the amphibole group of minerals occur in a wide range of p t environments and are common constituents of both igneous and metamorphic rocks. The chemical formulas for selected amphiboles from each of the four compositional groups are given in the. Amphiboles may also contain calcium, sodium, and lithium. The international mineralogical association presently classifies amphiboles as a mineral supergroup, inside which might be businesses and several subgroups.
Inosilicates double chain silicates the amphiboles. Amphibole is an important group of inosilicate minerals, forming prism or needlelike crystals. Amphibole group minerals physical optical properties. The mineral nomenclature of the amphiboles is divided into four principal subdivisions based on b group cation occupancy. These two schemes were produced to illustrate i the problems inherent in the classifi cation of a group of minerals as complicated as the.
Group of minerals that contain iron, magnesium, silicon, oxygen, and hydroxyl oh. Since the publication of the papers noted above, several new amphibole species have been described. This term has since been applied to the whole group. Amphibole, from the greek amphibolos, meaning ambiguous, was named by the famous french crystallographer and mineralogist renejust hauy 1801 in allusion to the great variety of composition and appearance shown by this mineral group. For example, the mineral amphibole is made up of a laundry list of elements including sodium, calcium, magnesium, iron, aluminum, silicon, and oxygen.
Mineralogy and morphology of amphiboles observed in soils and. Amphibole definition of amphibole by the free dictionary. Mineral chemical groups and formulae for rock forming minerals. Inosilicates pyroxenes and amphiboles tulane university.
Trace element variations in clinopyroxene and amphibole from alkaline to peralkaline syenites and granites. Pseudomorphs of hornblende group minerals, mainly actinolite, after a pyroxene group mineral, mainly augite. Yes, amphibole, also known as hornblende, is a darkcolored, inosilicate mineral, forming a prismshaped crystal. Amphibole from maderanertal, uri, switzerland fibrous green byssolite amphibole covering much of the specimen including a large clear quartz crystal. Minerals can be divided into their constituent elements. These usually serve to distinguish them from most other common rockforming minerals with the exception of the pyroxene mineral group.
Trace element variations in clinopyroxene and amphibole from. Nelson inosilicates pyroxenes and amphiboles inosilicates single chain silicates the single chain silicates have a basic structural unit consisting of linked sio4 tetrahedra that each share 2 of their oxygens in such a way as to build long chains of sio4. Most belong to the monoclinic crystal system, but some belong to the orthorhombic crystal system. The amphibole supergroup is divided into two groups according to the dominant w species. The minerals of the amphibole group crystallize in the orthorhombic, monoclinic, and triclinic systems, but the crystals of the different species are closely similar in many respects. The specimen shown is about two inches five centimeters across.
Amphibolite is a dark, heavy, metamorphic rock composed mostly of the mineral amphibole. The international mineralogical associations approved amphibole nomenclature has been revised in order to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely, and include new species of amphibole discovered and named since 1978, when the previous scheme was approved. Hornblende is the most common mineral in the amphibole group 29 cleavage angle for augite and hornblende 30 hornblende crystals. Minerals actinolitetremolite series are not stable, and can easily alter in the. Amphibole minerals defining characteristics are their dark color, hardness and welldeveloped cleavage. The amphiboles have prismatic cleavage with an angle of 56 and 124, which distinguishes it from the pyroxenes, which have an angle of 87 and 93 almost perpendicular. Amphibole asbestos an overview sciencedirect topics. However, some amphiboles exhibit a particularly good vitreous luster and may be mistaken as metallic.
The name pyroxene comes from the greek words for fire and stranger in a false allusion to their surprising presence in volcanic lavas. Environmental protection agency region 9 iag dw14921905012 openfile report 200662 u. The x represents large ions such as sodium or potassium and this site can be left vacant. Amphibole mineral data, information about amphibole, its properties and worldwide locations. Inosilicates are chain silicates which have interlocking chains of silicate tetrahedra with either sio3, 1. Amphibole is the name of an important group of generally darkcolored, inosilicate minerals, forming prism or needlelike crystals inosilicates are chain silicates which have interlocking chains of silicate tetrahedra with either sio3, 1. Amphibole definition of amphibole by merriamwebster. Amphibole definition and meaning collins english dictionary. Asbestos refers to serpentine and amphibole minerals in general. In 1997 leake presented a precise nomenclature of 76 names that encompass the chemical variation within this group.
Mineral chemistry and geothermometry of amphibole and. Any classification scheme, particularly one involving a supergroup of minerals as complicated as the amphiboles, is of necessity a compromise. Hornblende is a field and classroom name used for a group of darkcolored amphibole minerals found in many types of igneous and metamorphic rocks. Nomenclature of the amphibole supergroup mineralogical society. Amphibole group amethyst galleries mineral gallery. Although chrysotile asbestos, amphibole asbestos, and crionite fibers can all generate adverse health effects such as fibrosis, there has been recognition in many parts of the health community that the different forms are not equal in their pathogenicity, with amphibole asbestos and erionite generally considered more pathogenic or carcinogenic than chrysotile asbestos. Mineral groups international mineralogical association. The amphibole group of minerals is based on the doublechain silicate structure as. Introduction amphiboles are double chain silicates sharing many physical and chemical properties with pyroxenes. The group was so named by hauy in allusion to the protean variety, in composition and appearance, assumed by its minerals. Amphibole is an important group of generally darkcolored inosilicate minerals.
The classification is based on the a, b, and c groups of cations and the w group of anions, as these groups show the maximum compositional variability in the amphibole structure. Originally described from the urals region, russia. Asbestos is a collective name given to a group of minerals that naturally occur in a fiberlike shape and size. Amphibolite is a coarsegrained metamorphic rock that has amphibole minerals such as the hornblende group as its primary ingredient. Amphibole, any of a group of common rockforming silicate minerals. Askamineralogist from the mineralogical society of america s discussion groups original rockhounds discussion group rockhounds discussion group on. The mineral quartz is composed of two elements, silicon and oxygen. These minerals vary in chemical composition but are all doublechain inosilicates with very similar physical properties. Amphibole group an introduction to the rockforming.