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Anthophyllite

 
Anthophyllite

 
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Anthophyllite
 
 
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Anthophyllite is an amphibole
Amphibole

Amphibole defines an important group of generally dark-colored rock-forming Silicate minerals minerals, composed of double chain SiO4 tetrahedron, linked at the vertices and generally containing ions of iron and/or magnesium in their structures....
 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....
: (Mg, Fe)7Si8O22(OH)2, 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....
 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....
 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....
 hydroxide
Hydroxide

In chemistry, hydroxide is the name for the Diatomic molecule anion OH-, consisting of oxygen and hydrogen atoms, usually derived from the Dissociation of a base ....
. Anthophyllite is polymorphic
Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements....
 with cummingtonite
Cummingtonite

Cummingtonite or magnesium iron silicate hydroxide is a metamorphic amphibole with the chemical composition 7Silicon8Oxygen222....
. Some forms of anthophyllite are lamellar or fibrous and are used as asbestos
Asbestos

Asbestos is a naturally occurring silicate mineral with long, thin fibrous crystals. The word asbestos is derived from a Greek language adjective meaning inextinguishable....
. The name is derived from the Latin word anthophyllum, meaning clove, an allusion to the most common color of the mineral.

ophylite is the product of metamorphism
Metamorphic rock

Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form"....
 of 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....
-rich rocks especially ultrabasic igneous rock
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....
s and impure dolomitic
Dolomite

Dolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate calciummagnesium2 found in crystals....
 shale
Shale

Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
s.






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Encyclopedia


Anthophyllite is an amphibole
Amphibole

Amphibole defines an important group of generally dark-colored rock-forming Silicate minerals minerals, composed of double chain SiO4 tetrahedron, linked at the vertices and generally containing ions of iron and/or magnesium in their structures....
 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....
: (Mg, Fe)7Si8O22(OH)2, 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....
 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....
 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....
 hydroxide
Hydroxide

In chemistry, hydroxide is the name for the Diatomic molecule anion OH-, consisting of oxygen and hydrogen atoms, usually derived from the Dissociation of a base ....
. Anthophyllite is polymorphic
Polymorphism (materials science)

Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements....
 with cummingtonite
Cummingtonite

Cummingtonite or magnesium iron silicate hydroxide is a metamorphic amphibole with the chemical composition 7Silicon8Oxygen222....
. Some forms of anthophyllite are lamellar or fibrous and are used as asbestos
Asbestos

Asbestos is a naturally occurring silicate mineral with long, thin fibrous crystals. The word asbestos is derived from a Greek language adjective meaning inextinguishable....
. The name is derived from the Latin word anthophyllum, meaning clove, an allusion to the most common color of the mineral.

Occurrence

Anthophylite is the product of metamorphism
Metamorphic rock

Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form"....
 of 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....
-rich rocks especially ultrabasic igneous rock
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....
s and impure dolomitic
Dolomite

Dolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate calciummagnesium2 found in crystals....
 shale
Shale

Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
s. It also forms as a retrograde product rimming relict orthopyroxenes and olivine
Olivine

The mineral olivine is a magnesium iron Silicate minerals with the formula 2siliconoxygen4. It is one of the most common minerals on Earth, and has also been identified in meteorites and on the Moon, Mars, and comet Wild 2....
, and as an accessory mineral in cordierite
Cordierite

Cordierite or iolite is a magnesium iron aluminium Silicate minerals. Iron is almost always present and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: 2aluminum3 to 2Al3....
-bearing gneiss
Gneiss

Gneiss is a common and widely distributed type of Rock formed by high-grade regional metamorphic rock processes from pre-existing formations that were originally either igneous rock or Sedimentary rock rocks....
es and 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....
s. Anthophyllite also occurs as a retrograde metamorphic mineral derived from ultramafic rocks along with serpentine
Serpentine

The serpentine group describes a group of common rock-forming hydroxy magnesium iron Silicate minerals#Phyllosilicates minerals; they may contain minor amounts of other elements including chromium, manganese, cobalt and nickel....
. Geographically, it occurs in Pennsylvania, southwestern New Hampshire, central Massachusetts, Franklin, North Carolina, and in the Gravelly Range and Tobacco Root Mountains of southwest Montana.

Occurrence in ultramafic rocks

Anthophyllite is formed by the breakdown of talc
Talc

Talc is a mineral composed of hydrated magnesium silicate with the chemical formula Hydrogen2Magnesium34 or Magnesium3Silicon4Oxygen102....
 in ultramafic rocks in the presence of water and carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
 as a prograde metamorphic reaction
Metamorphic reaction

A metamorphic reaction is a chemical reaction that takes place during the geological process of metamorphism in an amalgamate of minerals that helps determine the final stable state of the resulting metamorphic rock....
. 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
Isograd

In geology, an isograd is a plane of constant metamorphic grade in the field; it separates metamorphic zones of different metamorphic index minerals....
.

Ultramafic rocks in purely hydrous, CO2-free environments will tend to form serpentine
Serpentine

The serpentine group describes a group of common rock-forming hydroxy magnesium iron Silicate minerals#Phyllosilicates minerals; they may contain minor amounts of other elements including chromium, manganese, cobalt and nickel....
-antigorite-brucite
Brucite

Brucite is the mineral form of magnesium hydroxide, with the chemical formula Magnesium2. It is pearly white or pale green in colour, translucent, with perfect cleavage, and tabular crystals or massive....
-tremolite
Tremolite

Tremolite is a member of the amphibole group of silicate minerals with composition: calcium2magnesium5silicon8oxygen222....
 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
Greenschist

Greenschist - also known as greenstone - is a general field petrology term applied to metamorphic rocks and/or altered mafic volcanic rock....
 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;

  • Olivine + Tremolite + Talc ? Olivine + Tremolite + Anthophyllite (low MgO, >550°C, XCO2 <0.6)
  • Talc + Tremolite + Magnesite ? Tremolite + Anthophyllite + Magnesite (High MgO, >500°C, XCO2 >0.6)
  • Talc + Magnesite + Tremolite ? Anthophyllite + Tremolite + Magnesite (Low MgO, >500°C, XCO2 >0.6)