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Chlorite group

General
Category Mineral
Chemical formula (Mg,Fe)3(Si,Al)4O10
(OH)2·(Mg,Fe)3(OH)6
Identification
Color Various shades of green; rarely yellow, red, or white. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes
Crystal habit Foliated masses, scaley aggregates, disseminated flakes. In Mineralogy, shape and size give rise to descriptive terms applied to the typical appearance or habit of Crystals The many terms used by mineralogists
Crystal system Monoclinic 2/m; with some triclinic polymorphs. A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions In Crystallography, the monoclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three vectors. In Crystallography, the triclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three basis vectors
Cleavage Perfect 001
Fracture Lamellar
Mohs Scale hardness 2 - 2. Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types In the field of Mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a Mineral is broken The Mohs scale of mineral hardness characterizes the scratch resistance of various Minerals through the ability of a harder material to scratch a softer material 5
Luster Vitreous, pearly, dull
Refractive index 1. Lustre (or luster) is a description of the way light interacts with the surface of a Crystal, rock, or Mineral. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium 57 -1. 67
Streak Pale green to grey
Specific gravity 2. The streak (also called powder color) of a Mineral is the Color of the powder produced when it is dragged across an unweathered surface Specific gravity is defined as the ratio of the Density of a given solid or liquid substance to the density of water at a specific temperature and pressure typically 6-3. 3
Other Characteristics Folia flexible - not elastic

The chlorites are a group of phyllosilicate minerals. The silicate minerals make up the largest and most important class of rock-forming Minerals They are classified based on the structure of their silicate Ion group A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific Chlorites can be described by the following four endmembers based on their chemistry via substitution of the following four elements in the silicate lattice; Mg, Fe, Ni, and Mn. A solid solution is a Solid - state Solution of one or more solutes in a Solvent.

In addition zinc, lithium and calcium species are known. The great range in composition results in considerable variation in physical, optical, and X-ray properties. X-ray scattering techniques are a family of non-destructive analytical techniques which reveal information about the crystallographic structure chemical composition Similarly, the range of chemical composition allows chlorite group minerals to exist over a wide range of temperature and pressure conditions. For this reason chlorite minerals are ubiquitous minerals within low and medium temperature metamorphic rocks, some igneous rocks, hydrothermal rocks and deeply buried sediments. Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat

Contents

Chlorite structure

The typical general formula is: (Mg,Fe)3(Si,Al)4O10(OH)2·(Mg,Fe)3(OH)6. This formula emphasises the structure of the group.

Chlorites have a 2:1 sandwich structure (2:1 sandwich layer = tetrahedral-octahedral-tetrahedral = t-o-t. . . ), this is often referred to as a talc layer. Talc (derived from the Persian via Arabic talq) is a Mineral composed of Hydrated Magnesium Silicate with Unlike other 2:1 clay minerals, a chlorite's interlayer space (the space between each 2:1 sandwich filled by a cation) is comprised of (Mg2+, Fe3+)(OH)6. An ion is an Atom or Molecule which has lost or gained one or more Valence electrons giving it a positive or negative electrical charge This (Mg2+, Fe3+)(OH)6 unit is more commonly referred to as the brucite-like layer, due to its closer resemblance to the mineral brucite (Mg(OH)2). Brucite is the Mineral form of Magnesium hydroxide, with the chemical formula Mg ( OH)2 Therefore, chlorite's structure appears as follows:

-t-o-t-brucite-t-o-t-brucite . . .

An older classification divided the chlorites into two subgroups: the orthochlorites and leptochlorites. The terms are seldom used and the ortho prefix is somewhat misleading as the chlorite crystal system is monoclinic and not orthorhombic.

Occurrence

Chlorite is commonly found in igneous rocks as an alteration product of mafic minerals such as pyroxene, amphibole, and biotite. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Mafic is an adjective describing a Silicate mineral or rock that is rich in magnesium and iron the term was derived by contracting "magnesium" and "ferric" The pyroxenes are a group of important rock-forming Silicate minerals found in many Igneous and metamorphic rocks. Amphibole (pronounced amfi-bowl defines an important group of generally dark-colored rock-forming inosilicate Minerals composed of double chain SiO4 Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F Chlorite is a common mineral associated with hydrothermal ore deposits and commonly occurs with epidote, sericite, adularia and sulfide minerals. Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining Epidote is a Calcium Aluminium Iron sorosilicate Mineral, Ca2Al2(Fe3+Al(SiO4(Si2O7O(OH Sericite is a fine grained Mica, either Muscovite, Illite, or Paragonite. Adularia is a tectosilicate mineral with formula K[[aluminum Al]] Si 3 O 8 A sulfide mineral is a Mineral containing Sulfide (S2- as the major Anion. In this environment chlorite may be a retrograde metamorphic alteration mineral of existing ferromagnesian minerals, or it may be present as a metasomatism product via addition of Fe, Mg, or other compounds into the rock mass. Metasomatism is the chemical alteration of a rock by Hydrothermal and other fluids Chlorite is also a common metamorphic mineral, usually indicative of low-grade metamorphism. Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change It is the diagnostic species of the zeolite facies and of lower greenschist facies. Zeolites (Greek zein, "to boil" lithos, "a stone" are hydrated Aluminosilicate Minerals and have a micro-porous structure Greenschist - also known as greenstone - is a general field petrologic term applied to metamorphic and/or altered Mafic Volcanic rock It occurs in the quartz, albite, sericite, chlorite, garnet assemblage of pelitic schist. Quartz (from German) is the most abundant Mineral in the Earth 's Continental crust (although Feldspar is more common in Albite is a plagioclase Feldspar Mineral. It is the sodium endmember of the Plagioclase Solid solution series Sericite is a fine grained Mica, either Muscovite, Illite, or Paragonite. The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives The schists form a group of medium-grade Metamorphic rocks chiefly notable for the preponderance of lamellar Minerals such as Micas chlorite Within ultramafic rocks, metamorphism can also produce predominantly clinochlore chlorite in association with talc. Talc (derived from the Persian via Arabic talq) is a Mineral composed of Hydrated Magnesium Silicate with Experiments indicate that chlorite can be stable in peridotite of the Earth's mantle above the ocean lithosphere carried down by subduction, and chlorite may even be present in the mantle volume from which island arc magmas are generated. The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided The lithosphere (IPA, from the Greek λίθος for "rocky" + σφαίρα for "sphere" is the solid outermost shell of a rocky Planet. In Geology, a subduction zone is an area on Earth where two tectonic plates meet and move towards one another with one sliding underneath the other A volcanic arc is a chain of volcanic islands or Mountains formed by Plate tectonics as an oceanic Tectonic plate subducts under Magma (Plurals magmas and magmata) is molten rock that sometimes forms beneath the surface of the Earth (or any other Terrestrial planet

Members of the Chlorite group:

Baileychlore (Zn,Fe+2,Al,Mg)6(Al,Si)4O10(O,OH)8
Chamosite (Fe,Mg)5Al(Si3Al)O10(OH)8
Clinochlore (Mg,Fe2+)5Al(Si3Al)O10(OH)8
Cookeite LiAl4(Si3Al)O10(OH)8
Donbassite Al2[Al2. 33][Si3AlO10](OH)8
Gonyerite (Mn,Mg)5(Fe+3)2Si3O10(OH)8
Nimite (Ni,Mg,Al)6(Si,Al)4O10(OH)8
Odinite (Fe,Mg,Al,Fe,Ti,Mn)2. 4(Al,Si)2O5OH4
Orthochamosite (Fe+2,Mg,Fe+3)5Al(Si3Al)O10(O,OH)8
Pennantite (Mn5Al)(Si3Al)O10(OH)8
Ripidolite (Mg,Fe,Al)6(Al,Si)4O10(OH)8
Sudoite Mg2(Al,Fe)3Si3AlO10(OH)8

Clinoclore, pennantite, and chamosite are the most common varieties. Several other sub-varieties have been described.

The name chlorite is from the Greek chloros, meaning "green", in reference to its color. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly

See also

References

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