Amphibole

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Amphibole

Amphibole (pronounced amfi-bowl) defines an important group of generally dark-colored rock-forming inosilicate

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
mineral

Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
s, composed of double chain SiO₄ tetrahedra

Tetrahedron

A tetrahedron is a polyhedron composed of four triangle faces, three of which meet at each vertex . A regular tetrahedron is one in which the four triangles are regular, or "equilateral", and is one of the Platonic solids....
, linked at the vertices and generally containing ion

Ion

An ion is an atom or molecule which has lost or gained one or more electrons, giving it a positive or negative electrical charge. According to the Bohr_model this will be from or in the outer shield 'n'....
s of iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
and/or magnesium

Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
in their structures. Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic.

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Encyclopedia

Amphibole (pronounced amfi-bowl) defines an important group of generally dark-colored rock-forming inosilicate

Silicate minerals

The silicate minerals make up the largest and most important class of rock-forming minerals, comprising approximately 90 percent of the crust of the Earth....
mineral

Mineral

Tetrahedron

Ion

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
and/or magnesium

Magnesium

Pyroxene

The pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rock rock . They share a common structure comprised of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems....
s. The chief differences from pyroxenes are that (i) amphiboles 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

Pleochroism

Pleochroism is an optical phenomenon in which mineral grains within a Rock appear to be different colors when observed at different angles under a polarization petrographic microscope....
and by the smaller angle of extinction (Z angle c) on the plane of symmetry. Amphiboles are the primary constituent of amphibolite

Amphibolite

Amphibolite is the name given to a Rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks....
s.

Amphiboles are minerals of either igneous

Igneous rock

Igneous rock is one of the three main Rock types . Igneous rock is formed by magma being cooled and becoming solid . They may form with or without crystallization, either below the surface as Intrusion rocks or on the surface as extrusive rocks....
or metamorphic

Metamorphism

Metamorphism is the solid-state Crystallization of pre-existing Rock due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids....
origin; in the former case occurring as constituents (hornblende

Hornblende

Hornblende is a complex silicate minerals series of minerals. Hornblende is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
) of igneous rocks, such as granite

Granite

Granite is a common and widely occurring type of Intrusion , felsic, igneous rock rock . Granite has a medium to coarse texture, occasionally with some individual crystals larger than the groundmass forming a rock known as Porphyry ....
, diorite

Diorite

Diorite is a grey to dark grey intermediate Intrusion igneous rock composed principally of plagioclase feldspar , biotite, hornblende, and/or pyroxene....
, andesite

Andesite

Andesite is an igneous rock, volcanic rock, of Igneous rock#Chemical classification, with aphanitic to porphyritic texture. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende....
and others. Those of metamorphic origin include examples such as those developed in limestone

Limestone

File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record....
s by contact metamorphism (tremolite

Tremolite

Tremolite is a member of the amphibole group of silicate minerals with composition: calcium2magnesium5silicon8oxygen222....
) and those formed by the alteration of other ferromagnesian minerals (hornblende). Pseudomorphs of amphibole after pyroxene are known as uralite.

The name amphibole (Greek

Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
aµf?ß???? - amphibolos meaning 'ambiguous') was used by RJ Haüy

René Just Haüy

Ren? Just Ha?y was a France mineralogist, commonly styled the Abb? Ha?y after he was made an honorary canon of Notre-Dame de Paris....
to include tremolite, actinolite, tourmaline and hornblende. The group was so named by Haüy in allusion to the protean variety, in composition and appearance, assumed by its minerals. This term has since been applied to the whole group. Numerous sub-species and varieties are distinguished, the more important of which are tabulated below in two series. The formulae of each will be seen to be built on the general double-chain silicate

Silicate

A silicate is a compound containing an anion in which one or more central silicon atoms are surrounded by electronegative ligands. This definition is broad enough to include species such as hexafluorosilicate , [SiF6]2-, but the silicate species that are encountered most often consist of silicon with oxygen as the ligand...
formula RSi₄O₁₁.

Mineral species

Chemical formulae

Orthorhombic series

Anthophyllite
Anthophyllite

Anthophyllite is an amphibole mineral: 7Si8O222, magnesium iron Silicate minerals hydroxide. Anthophyllite is polymorphism with cummingtonite....
(Mg,Fe)₇Si₈O₂₂(OH)₂

Monoclinic series

Tremolite
Tremolite

Tremolite is a member of the amphibole group of silicate minerals with composition: calcium2magnesium5silicon8oxygen222....
Ca₂Mg₅Si₈O₂₂(OH)₂
Actinolite
Actinolite

Actinolite is an amphibole silicate minerals with the chemical formula ....
Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂
Cummingtonite
Cummingtonite

Cummingtonite or magnesium iron silicate hydroxide is a metamorphic amphibole with the chemical composition 7Silicon8Oxygen222....
Fe₂Mg₅Si₈O₂₂(OH)₂
Grunerite
Grunerite

Grunerite is a mineral of the amphibole group of minerals with formula Iron7Silicon8Oxygen222. It is the iron endmember of the grunerite-cummingtonite series....
Fe₇Si₈O₂₂(OH)₂
Hornblende
Hornblende

Hornblende is a complex silicate minerals series of minerals. Hornblende is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
Ca₂(Mg,Fe,Al)₅(Al,Si)₈O₂₂(OH)₂
Glaucophane
Glaucophane

Glaucophane is a mineral belonging to the amphibole group, chemical formula sodium23aluminum2silicon8oxygen222....
Na₂(Mg,Fe)₃Al₂Si₈O₂₂(OH)₂
Riebeckite
Riebeckite

Riebeckite is a sodium-rich member of the amphibole group of minerals, chemical formula sodium25silicon8oxygen222....
Na₂Fe²⁺₃Fe³⁺₂Si₈O₂₂(OH)₂
Arfvedsonite
Arfvedsonite

Arfvedsonite is a sodium amphibole mineral with composition: Na34FeSi8O222: sodium, iron, magnesium, Silicate minerals, hydroxide....
Na₃Fe²⁺₄Fe³⁺Si₈O₂₂(OH)₂
Crocidolite Na₂Fe²⁺₃Fe³⁺₂Si₈O₂₂(OH)₂
Richterite Na₂Ca(Mg,Fe)₅Si₈O₂₂(OH)₂
Pargasite
Pargasite

Pargasite is a complex Silicate mineral mineral with formula NaCa24AlO222.It was first described for an occurrence in Pargas, Finland in 1814 and named for the locality....
NaCa₂Mg₃Fe²⁺Si₆Al₃O₂₂(OH)₂

Descriptions

On account of the wide variations in chemical composition, the different members vary considerably in properties and general appearance.

Anthophyllite

Anthophyllite

Anthophyllite is an amphibole mineral: 7Si8O222, magnesium iron Silicate minerals hydroxide. Anthophyllite is polymorphism with cummingtonite....
occurs as brownish, fibrous or lamellar masses with hornblende in mica

Mica

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic with a tendency towards pseudo-hexagonal crystals and are similar in chemical composition....
-schist

Schist

The schists form a group of Erins metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, Chlorite group, talc, hornblende, graphite, and others....
at Kongsberg

Kongsberg

is a List of cities in Norway and Municipalities of Norway in Buskerud Counties of Norway, Norway. It is located at the southern end of the Districts of Norway of Numedal....
in Norway

Norway

Norway , officially the Kingdom of Norway, is a constitutional monarchy in Northern Europe that occupies the western portion of the Scandinavian Peninsula....
and some other localities. An aluminous related species is known as gedrite

Gedrite

Gedrite is a silicate mineral of the amphibole group with formula: 2[3Al2]O222. Gedrite occurs in Contact metamorphism and medium to high grade metamorphic rocks in association with garnet, cordierite, anthophyllite, cummingtonite, sapphirine, sillimanite, kyanite, quartz, staurolite and...
and a deep green Russia

Russia

Russia , or the Russian Federation , is a list of countries spanning more than one continent country extending over much of northern Eurasia....
n variety containing little iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. Iron is a Group 8 element and period 4 element. Iron is lustrous and silvery in color....
as kupfferite.

Hornblende

Hornblende

Amphibolite

Amphibolite is the name given to a Rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks....
s formed by metamorphism of basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually gray to black and fine-grained due to rapid cooling of lava at the surface of a planet....
.

Actinolite

Actinolite

Actinolite is an amphibole silicate minerals with the chemical formula ....
is an important and common member of the monoclinic series, forming radiating groups of acicular crystals of a bright green or greyish-green color. It occurs frequently as a constituent of greenschist

Greenschist

Greenschist - also known as greenstone - is a general field petrology term applied to metamorphic rocks and/or altered mafic volcanic rock....
s. The name (from Greek

Ancient Greek

Ancient Greek is the historical stage in the development of the Greek language spanning across the Archaic Greece , Classical Greece , and Hellenistic civilization periods of ancient Greece and the classical antiquity....
a?t??/aktis, a 'ray' and ?????/lithos, a 'stone') is a translation of the old German

German language

German is a West Germanic languages, thus related to and classified alongside English language and Dutch language. It is one of the world's world language and the most widely spoken mother tongue in the European Union....
word Strahlstein (radiated stone).

Glaucophane

Glaucophane

Glaucophane is a mineral belonging to the amphibole group, chemical formula sodium23aluminum2silicon8oxygen222....
, crocidolite, riebeckite

Riebeckite

Riebeckite is a sodium-rich member of the amphibole group of minerals, chemical formula sodium25silicon8oxygen222....
and arfvedsonite

Arfvedsonite

Arfvedsonite is a sodium amphibole mineral with composition: Na34FeSi8O222: sodium, iron, magnesium, Silicate minerals, hydroxide....
form a somewhat special group of alkali-amphiboles. The first two are blue fibrous minerals, with glaucophane occurring in blueschist

Blueschist

Blueschist is a Rock that forms by the metamorphism of basalt and rocks with similar composition at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius....
s and crocidolite (blue asbestos) in ironstone formations, both resulting from dynamo-metamorphic processes. The latter two are dark green minerals, which occur as original constituents of igneous rocks rich in sodium, such as nepheline

Nepheline

Nepheline, also called nephelite , is a feldspathoid: a silica-undersaturated aluminosilicate, Sodium3PotassiumAluminium4silicon4Oxygen16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites....
-syenite

Syenite

Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts ....
and phonolite

Phonolite

Phonolite is an evolved lava which is considered as forming in shallow magma chambers. Phonolite is an igneous rock, volcanic rock , of intermediate composition, with aphanitic to porphyritic texture....
.

Pargasite

Pargasite

Pargasite is a complex Silicate mineral mineral with formula NaCa24AlO222.It was first described for an occurrence in Pargas, Finland in 1814 and named for the locality....
is a rare magnesium-rich amphibole with essential sodium

Sodium

Sodium is an element which has the symbol Na , atomic number 11, atomic mass 23 amu , and a common oxidation number +1. Sodium is a soft, silvery white, highly reactive element and is a member of the alkali metals within "group 1" ....
, usually found in ultramafic rocks. For instance, it occurs in uncommon mantle

Mantle (geology)

The mantle is a part of an astronomical object. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers....
xenolith

Xenolith

A xenolith is a rock fragment which becomes enveloped in a larger rock during the latter's development and hardening. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement and eruption....
s, carried up by kimberlite

Kimberlite

Kimberlite is a type of potassic volcanic rock best known for sometimes containing diamonds. It is named after the town of Kimberley, Northern Cape in South Africa, where the discovery of an diamond in 1871 spawned a diamond rush, eventually creating the Big Hole....
. It is hard, dense, black and usually idiomorphic, with a red-brown pleochroism

Pleochroism

Petrography

Petrography is that branch of petrology which focuses on detailed descriptions of rock . Someone who studies petrography is called a petrographer....
thin section

Thin section

In optical mineralogy and petrography, a thin section is a laboratory preparation of a Rock , mineral or soil sample for use with a polarization petrographic microscope....
.

Amphibole

Mineral species

Chemical formulae

Descriptions

See also