Anthophyllite is an orthorhombicamphibolemineral: ☐Mg2Mg5Si8O22(OH)2 (☐ is for a vacancy, a point defect in the crystal structure), magnesiumironinosilicatehydroxide. Anthophyllite is polymorphic with cummingtonite. Some forms of anthophyllite are lamellar or fibrous and are classed as asbestos. The name is derived from the Latin word anthophyllum, meaning clove, an allusion to the most common color of the mineral. The Anthophyllite crystal is characterized by its perfect cleavage along directions 126 degrees and 54 degrees.
Anthophyllite is formed by the breakdown of talc in ultramafic rocks in the presence of water and carbon dioxide as a prograde metamorphic reaction. The partial pressure of carbon dioxide (XCO2) in aqueous solution favors production of anthophyllite. Higher partial pressures of CO2 reduces the temperature of the anthophyllite-inisograd.
Ultramafic rocks in purely hydrous, CO2-free environments will tend to form serpentinite-antigorite-brucite-tremolite assemblages (dependent on MgO content) or at amphibolite to granulite metamorphic grade, metamorphic pyroxene or olivine. Thus, metamorphic assemblages of ultramafic rocks containing anthophyllite are indicative of at least greenschist facies metamorphism in the presence of carbon dioxide bearing metamorphic fluids.
The typical metamorphic assemblage reactions for low-magnesian (<25% MgO) and high-magnesian (>25% MgO) ultramafic rocks are;
Anthophyllite in serpentinised komatiite, Maggie Hays Ni Mine, Western Australia
Retrogressive anthophyllite is relatively rare in ultramafic rocks and is usually poorly developed due to the lower energy state available for metamorphic reactions to progress and also the general dehydration of rock masses during metamorphism. Similarly, the need for substantial components of carbon dioxide in metamorphic fluid restricts the appearance of anthophyllite as a retrograde mineral. The usual metamorphic assemblage of retrograde-altered ultramafic rocks is thus usually a serpentinite or talc-magnesite assemblage.
Retrograde anthophyllite is present most usually in shear zones where fracturing and shearing of the rocks provides a conduit for carbonated fluids during retrogression.
Fibrous anthophyllite is one of the six recognised types of asbestos. It was mined in Finland and also in Matsubase, Japan where a large-scale open-cast asbestos mine and mill was in operation between 1883 and 1970.
In Finland anthophyllite asbestos was mined in two mines, the larger one Paakkila in the Tuusniemi commune started in 1918 and closed in 1975 due to the dust problems. The smaller mine, Maljasalmi in the commune of Outokumpu, was mined from 1944 to 1952. The anthophyllite was used in asbestos cement and for insulation, roofing material etc.
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January 01, 1970
anthophyllite, orthorhombic, amphibole, mineral, mg2mg5si8o22, vacancy, point, defect, crystal, structure, magnesium, iron, inosilicate, hydroxide, polymorphic, with, cummingtonite, some, forms, anthophyllite, lamellar, fibrous, classed, asbestos, name, derive. Anthophyllite is an orthorhombic 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 are lamellar or fibrous and are classed as asbestos The name is derived from the Latin word anthophyllum meaning clove an allusion to the most common color of the mineral The Anthophyllite crystal is characterized by its perfect cleavage along directions 126 degrees and 54 degrees AnthophylliteGeneralCategoryInosilicatesAmphiboleFormula repeating unit Mg2Mg5Si8O22 OH 2IMA symbolAth 1 Strunz classification9 DE 05Crystal systemOrthorhombicCrystal classDipyramidal mmm H M symbol 2 m 2 m 2 m Space groupPnmaUnit cella 18 5 b 17 9c 5 28 A Z 4IdentificationColorGray to green brown and beigeCrystal habitRarely as distinct crystals Commonly lamellar or fibrous CleavagePerfect on 210 imperfect on 010 100 TenacityBrittle elastic when fibrousMohs scale hardness5 5 6LusterVitreous pearly on cleavageStreakWhite to grayDiaphaneityTransparent to translucentSpecific gravity2 85 3 2Optical propertiesBiaxial Refractive indexna 1 598 1 674 nb 1 605 1 685 ng 1 615 1 697 indices increase with Fe contentBirefringenced 0 017 0 0232V angle57 90 Diagnostic featuresCharacterized by clove brown color but unless in crystals difficult to distinguish from other amphiboles without optical and or X ray testsReferences 2 3 4 5 6 7 Contents 1 Occurrence 2 Occurrence in ultramafic rocks 3 Fibrous anthophyllite 4 ReferencesOccurrence editAnthophyllite is the product of metamorphism of magnesium rich rocks especially ultrabasic igneous rocks and impure dolomitic shales It also forms as a retrograde product rimming relict orthopyroxenes and olivine and as an accessory mineral in cordierite bearing gneisses and schists Anthophyllite also occurs as a retrograde metamorphic mineral derived from ultramafic rocks along with serpentinite Occurrence in ultramafic rocks editAnthophyllite is formed by the breakdown of talc in ultramafic rocks in the presence of water and carbon dioxide as a prograde metamorphic reaction The partial pressure of carbon dioxide XCO2 in aqueous solution favors production of anthophyllite Higher partial pressures of CO2 reduces the temperature of the anthophyllite in isograd Ultramafic rocks in purely hydrous CO2 free environments will tend to form serpentinite antigorite brucite tremolite assemblages dependent on MgO content or at amphibolite to granulite metamorphic grade metamorphic pyroxene or olivine Thus metamorphic assemblages of ultramafic rocks containing anthophyllite are indicative of at least greenschist facies metamorphism in the presence of carbon dioxide bearing metamorphic fluids The typical metamorphic assemblage reactions for low magnesian lt 25 MgO and high magnesian gt 25 MgO ultramafic rocks are Olivine Tremolite Talc Olivine Tremolite Anthophyllite low MgO gt 550 C XCO2 lt 0 6 Talc Tremolite Magnesite Tremolite Anthophyllite Magnesite High MgO gt 500 C XCO2 gt 0 6 Talc Magnesite Tremolite Anthophyllite Tremolite Magnesite Low MgO gt 500 C XCO2 gt 0 6 nbsp Anthophyllite in serpentinised komatiite Maggie Hays Ni Mine Western Australia Retrogressive anthophyllite is relatively rare in ultramafic rocks and is usually poorly developed due to the lower energy state available for metamorphic reactions to progress and also the general dehydration of rock masses during metamorphism Similarly the need for substantial components of carbon dioxide in metamorphic fluid restricts the appearance of anthophyllite as a retrograde mineral The usual metamorphic assemblage of retrograde altered ultramafic rocks is thus usually a serpentinite or talc magnesite assemblage Retrograde anthophyllite is present most usually in shear zones where fracturing and shearing of the rocks provides a conduit for carbonated fluids during retrogression Fibrous anthophyllite edit nbsp Anthophyllite fibers SEM micrograph Fibrous anthophyllite is one of the six recognised types of asbestos It was mined in Finland and also in Matsubase Japan where a large scale open cast asbestos mine and mill was in operation between 1883 and 1970 In Finland anthophyllite asbestos was mined in two mines the larger one Paakkila in the Tuusniemi commune started in 1918 and closed in 1975 due to the dust problems The smaller mine Maljasalmi in the commune of Outokumpu was mined from 1944 to 1952 The anthophyllite was used in asbestos cement and for insulation roofing material etc Anthophyllite is also known as azbolen asbestos References edit Warr L N 2021 IMA CNMNC approved mineral symbols Mineralogical Magazine 85 3 291 320 Bibcode 2021MinM 85 291W doi 10 1180 mgm 2021 43 S2CID 235729616 Handbook of Mineralogy Mindat org Webmineral data Klein Cornelius 2002 The Manual of Mineral Science 22nd ed John Wiley amp Sons Inc ISBN 0 471 25177 1 IMA Master List Archived from the original on 2015 01 05 Retrieved 2014 05 12 Anthophyllite nbsp Wikimedia Commons has media related to Anthophyllite Retrieved from https en wikipedia org w index php title Anthophyllite amp oldid 1173430545, wikipedia, wiki, book, books, library,
