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Amphibole () is a group of
inosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide) is usually conside ...
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
s, forming prism or needlelike crystals, composed of double chain
tetrahedra In geometry Geometry (from the grc, γεωμετρία; ' "earth", ' "measurement") is, with , one of the oldest branches of . It is concerned with properties of space that are related with distance, shape, size, and relative position ...

tetrahedra
, linked at the vertices and generally containing
ion An ion () is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
s of
iron Iron () is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

iron
and/or
magnesium Magnesium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

magnesium
in their structures. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The
International Mineralogical Association Founded in 1958, the International Mineralogical Association (IMA) is an international group of 40 national societies. The goal is to promote the science of mineralogy Mineralogy is a subject of geology Geology (from the Ancient Greek γῆ, ...
currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups.


Mineralogy

Amphiboles crystallize into two crystal systems,
monoclinic In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek language, Greek words ''crystallon'' " ...

monoclinic
and
orthorhombic In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek language, Greek words ''crystallon'' "col ...

orthorhombic
. In chemical composition and general characteristics they are similar to the
pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming Silicate minerals#Inosilicates, inosilicate minerals found in many Igneous rock, igneous and metamorphic rock, metamorphic rock (geology), rocks. Pyroxenes have t ...
s. The chief differences from pyroxenes are that (i) amphiboles contain essential hydroxyl (OH) or halogen (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. Amphiboles are the primary constituent of
amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase. Amphibolite is a grouping of rocks composed mainly of amphibole and plagioclase feldspar, with little or no quartz. It ...

amphibolite
s.


In rocks

Amphiboles are minerals of either
igneous Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock i ...
or
metamorphic Metamorphic rocks arise from the transformation of existing rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the mineral ...
origin. Amphiboles are more common in intermediate to
felsic In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes ...
igneous rocks than in
mafic A mafic mineral or rock is a silicate mineral Silicate minerals are rock-forming mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composit ...
igneous rocks, because the higher
silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any su ...

silica
and dissolved water content of the more
evolved Evolution is change in the heritable Heredity, also called inheritance or biological inheritance, is the passing on of Phenotypic trait, traits from parents to their offspring; either through asexual reproduction or sexual reproduction, ...
magmas favors formation of amphiboles rather than pyroxenes. The highest amphibole content, around 20%, is found in
andesite Andesite ( or ) is an extrusive volcanic rock of intermediate composition. In a general sense, it is the intermediate type between basalt and rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of so ...

andesite
s.
Hornblende Hornblende is a complex inosilicate series of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock ...

Hornblende
is widespread in igneous and metamorphic rocks and is particularly common in
syenite Image:Nepheline-syenite-2005.jpg, Leucocratic variety of nepheline syenite from Sweden (särnaite) Syenite is a coarse-grained Intrusion, intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, ...

syenite
s and
diorite Diorite ( ) is an intrusive rock, intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals. It is Intermediate composition, inter ...

diorite
s. Calcium is sometimes a constituent of naturally occurring amphiboles. Amphilotes of metamorphic origin include those developed in
limestone Limestone is a common type of carbonate In chemistry, a carbonate is a salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of Salt (chemistry), salts; salt in its na ...

limestone
s by contact metamorphism (
tremolite Tremolite is a member of the amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containin ...

tremolite
) and those formed by the alteration of other ferromagnesian minerals (such as hornblende as an alteration product of pyroxene).
Pseudomorph In mineralogy Mineralogy is a subject of geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks o ...

Pseudomorph
s of amphibole after pyroxene are known as uralite.


History and etymology

The name amphibole (
Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), generally referred to by speakers simply as Greek (, ), refers collectively to the diale ...
''ἀμφίβολος - amphíbolos'' literally meaning 'double entendre', implying ambiguousness) was used by
René Just Haüy René Just Haüy () FRS MWS FRSE (28 February 1743 – 3 June 1822) was a French priest and mineralogist Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical ...

René Just Haüy
to include tremolite,
actinolite Actinolite is an amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containing ions of ir ...

actinolite
and
hornblende Hornblende is a complex inosilicate series of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock ...

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 In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds composed of atoms, ...
formula RSi4O11. Four of the amphibole minerals are among the minerals commonly called
asbestos Asbestos (pronounced: or ) is a naturally occurring fibrous silicate mineral Silicate minerals are rock-forming mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fair ...
. These are: anthophyllite, riebeckite, cummingtonite/grunerite series, and actinolite/tremolite series. The cummingtonite/grunerite series is often termed amosite or brown asbestos; riebeckite is known as crocidolite or blue asbestos. These are generally called amphibole asbestos. Mining, manufacture and prolonged use of these minerals can cause serious illnesses.


Mineral species


Chemical formula

Orthorhombic series *
Anthophyllite Anthophyllite is an amphibole mineral: ☐Mg2Mg5Si8O22(OH)2 (☐ is for a vacancy, a point defect in the crystal structure), magnesium iron inosilicate hydroxide. Anthophyllite is polymorphic with cummingtonite. Some forms of anthophyllite ar ...

Anthophyllite
, (Fe,Mg)7Si8O22(OH)2 *
Holmquistite
Holmquistite
, Li2Mg3Al2Si8O22(OH)2 * Ferrogedrite, Fe2+5Al4Si6O22(OH)2 Monoclinic series *
Tremolite Tremolite is a member of the amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containin ...

Tremolite
, Ca2Mg5Si8O22(OH)2 *
Actinolite Actinolite is an amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containing ions of ir ...

Actinolite
, Ca2(Mg,Fe)5Si8O22(OH)2 * Cummingtonite, Fe2Mg5Si8O22(OH)2 *
Grunerite Grunerite is a mineral of the amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containing ...
, Fe7Si8O22(OH)2 *
Hornblende Hornblende is a complex inosilicate series of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock ...

Hornblende
, (K,Na)0-1(Ca,Na,Fe,Mg)2(Mg,Fe,Al)5(Al,Si)8O22(OH)2 *
Glaucophane Glaucophane is the name of a mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks o ...

Glaucophane
, Na2(Mg,Fe)3Al2Si8O22(OH)2 *
Riebeckite Riebeckite is a sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms th ...

Riebeckite
(or
Crocidolite Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula Na2(Fe2+3Fe3+2)Si8O22(OH)2. It forms a solid solution series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long pris ...
), Na2Fe2+3Fe3+2Si8O22(OH)2 *
Arfvedsonite Arfvedsonite is a sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms ...

Arfvedsonite
, Na3Fe2+4Fe3+Si8O22(OH)2 * Richterite, Na2Ca(Mg,Fe)5Si8O22(OH)2 *
Pargasite
Pargasite
, NaCa2Mg3Fe2+Si6Al3O22(OH)2 * Winchite, (CaNa)Mg4(Al,Fe3+)Si8O22(OH)2 *
Edenite Edenite is a Inosilicate#Inosilicates, double chain silicate mineral of the amphibole group with the general chemical composition NaCa2Mg5(Si7Al)O22(OH)2. Edenite is named for the locality of Edenville, Orange County, New York, where it was first d ...
, NaCa2Mg5(Si7Al)O22(OH)2 *
Kaersutite
Kaersutite
, NaCa2(Mg3Ti4+Al)(Si6Al2)O22(OH)2


Descriptions

On account of the wide variations in chemical composition, the different members vary considerably in properties and general appearance.
Anthophyllite Anthophyllite is an amphibole mineral: ☐Mg2Mg5Si8O22(OH)2 (☐ is for a vacancy, a point defect in the crystal structure), magnesium iron inosilicate hydroxide. Anthophyllite is polymorphic with cummingtonite. Some forms of anthophyllite ar ...

Anthophyllite
occurs as brownish, fibrous or lamellar masses with hornblende in
mica Micas ( ) are a group of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs natural ...

mica
-
schist Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fair ...

schist
at
Kongsberg Kongsberg () is a List of cities in Norway, town and Municipalities of Norway, municipality in Viken (county), Viken Counties of Norway, county, Norway. Kongsberg is the administration center in Kongsberg municipality. The city is located on the r ...
in
Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the Norwegian language Norwegian (Norwegian: ''norsk'') is a Nort ...

Norway
and some other localities. An aluminous related species is known as gedrite and a deep green
Russia Russia ( rus, link=no, Россия, Rossiya, ), or the Russian Federation, is a country spanning Eastern Europe Eastern Europe is the eastern region of . There is no consistent definition of the precise area it covers, partly because th ...

Russia
n variety containing little
iron Iron () is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

iron
as kupfferite.
Hornblende Hornblende is a complex inosilicate series of mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock ...

Hornblende
is an important constituent of many igneous rocks. It is also an important constituent of
amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase. Amphibolite is a grouping of rocks composed mainly of amphibole and plagioclase feldspar, with little or no quartz. It ...

amphibolite
s formed by metamorphism of
basalt Basalt (, ) is a fine-grained extrusive A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope Extr ...

basalt
.
Actinolite Actinolite is an amphibole Amphibole () is a group of Silicate minerals, inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedron, tetrahedra, linked at the vertices and generally containing ions of ir ...

Actinolite
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 Greenschists are metamorphic rocks that formed under the lowest temperatures and pressures usually produced by regional metamorphism, typically and 2–10 kilobars (). Greenschists commonly have an abundance of green minerals such as chlorite, ...
s. The name (from
Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approximately 10.7 million as of ...
''ἀκτίς, ἀκτῖνος/aktís, aktînos'', a 'ray' and ''λίθος/líthos'', a 'stone') is a translation of the old
German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nationality law * German language The German la ...

German
word ''Strahlstein'' (radiated stone).
Glaucophane Glaucophane is the name of a mineral In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks o ...

Glaucophane
,
crocidolite Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula Na2(Fe2+3Fe3+2)Si8O22(OH)2. It forms a solid solution series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long pris ...
,
riebeckite Riebeckite is a sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms th ...

riebeckite
and
arfvedsonite Arfvedsonite is a sodium Sodium is a chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms ...

arfvedsonite
form a somewhat special group of alkali-amphiboles. The first two are blue fibrous minerals, with glaucophane occurring in
blueschist of a thin section vein in mica Mica is a group of sheet silicate minerals, not to be confused with Micah. Mica or MICA may also refer to: Companies * Mica DIY, a UK Retailer Co-operative, Symbol group Acronyms * Mahone Islands Conser ...
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, also called nephelite (from Greek: νεφέλη, "cloud"), is a rock forming mineral in the feldspathoid group: a silica-undersaturated aluminosilicate, Na3K Al4Si4 O16, that occurs in intrusive and volcanic rocks with low silica, ...

nepheline
-
syenite Image:Nepheline-syenite-2005.jpg, Leucocratic variety of nepheline syenite from Sweden (särnaite) Syenite is a coarse-grained Intrusion, intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, ...

syenite
and
phonolite Phonolite is an uncommon extrusive rock, of intermediate composition, intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Its intrusive ro ...
. is a rare magnesium-rich variety of hornblende with essential
sodium Sodium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

sodium
, usually found in
ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch ...
rocks. For instance, it occurs in uncommon
mantle Mantle may refer to: *Mantle (geology) A mantle is a layer inside a planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a n ...
xenolithImage:XenolithSierra.JPG, Gabbroic xenolith in granite in Rock Creek Canyon, eastern Sierra Nevada (U.S.), Sierra Nevada, California A xenolith ("foreign rock") is a rock (geology), rock fragment (country rock) that becomes enveloped in a larger ro ...
s, carried up by
kimberlite Cross-section of kimberlite from South Africa. The kimberlite matrix is made up of clay minerals and carbonates, presented in blue, purple and buff colours. Kimberlite is an igneous rock, which sometimes contains diamonds. It is named after the ...

kimberlite
. It is hard, dense, black and usually automorphic, with a red-brown
pleochroism Pleochroism (from Greek wikt:πλείων#Ancient Greek, πλέων, ''pléōn'', "more" and wikt:χρώμα#Ancient Greek, χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at d ...
in
petrographic Petrography is a branch of petrology Image:LvMS-Lvm.jpg, A volcanic lithic fragment (geology), sand grain seen under the microscope, with plane-polarized light in the upper picture, and cross polarized light in the lower picture. Scale box is 0. ...
thin section vein in mica Micas ( ) are a group of minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect Cleavage (crystal) ...
.


See also

*
List of minerals This is a list of minerals for which there are articles on Wikipedia. Mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specif ...
*
Classification of minerals - Silicates This list gives an overview of the classification of minerals (silicates) and includes mostly IMA recognized minerals and its groupings. This list complements the alphabetical list on List of minerals approved by IMA Mineralogy Mineralogy is a s ...


Notes


References

* C. Michael Hogan. 2010
''Calcium''. eds. A.Jorgensen, C. Cleveland. Encyclopedia of Earth
National Council for Science and the Environment. * Cornelius S. Hurlbut and Cornelis Klein. 1985. ''Manual of Mineralogy'', 20th ed., John Wiley and Sons, New York {{Authority control Inosilicates Asbestos