Kyanite

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Kyanite

Kyanite, whose name derives from the Greek word kyanos, meaning blue, is a typically blue 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...
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....
, commonly found in aluminium

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
-rich metamorphic pegmatite

Pegmatite

Pegmatite is a very coarse-grained igneous rock that has a grain size of 20 mm or more; such rocks are referred to as pegmatitic.Most pegmatites are composed of quartz, feldspar and mica; in essence a "granite"....
s and/or sedimentary rock

Sedimentary rock

Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
. Kyanite is a diagnostic mineral of the Blueschist Facies of metamorphic

Metamorphic

The term Metamorphic can be associated with a number of meanings:*Metamorphic rock: The term for rocks that have been transformed by extreme heat and pressure....
rocks.

Kyanite is a member of the aluminosilicate series, which also includes the polymorph

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....
andalusite

Andalusite

Andalusite is an aluminium Silicate minerals mineral with the chemical formula Al2SiO5.The variety chiastolite commonly contains dark inclusions of carbon or clay which form a checker-board pattern when shown in cross-section....
and the polymorph sillimanite

Sillimanite

Sillimanite also called Bucholzite is an alumino-silicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman ....
. Kyanite is strongly anisotropic

Anisotropy

Anisotropy is the property of being directionally dependent, as opposed to isotropy, which means homogeneity in all directions. It can be defined as a difference in a physical property for some material when measured along different axes....
, in that its hardness

Mohs scale of mineral hardness

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Encyclopedia

Kyanite, whose name derives from the Greek word kyanos, meaning blue, is a typically blue silicate

Silicate

Mineral

Aluminium

Aluminium or aluminum is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13....
-rich metamorphic pegmatite

Pegmatite

Sedimentary rock

Metamorphic

Polymorphism (materials science)

Andalusite

Sillimanite

Anisotropy

Mohs scale of mineral hardness

Not to be confused with Siemens_#Mho, a unit of electric conductance.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....
varies depending on its crystallographic direction. While this is a feature of almost all minerals, in kyanite this anisotropism can be considered an identifying characteristic.

At temperatures above 1100 °C, kyanite decomposes

Chemical decomposition

Chemical decomposition or analysis is the separation of a chemical compound into chemical element or smaller compounds. It is sometimes defined as the opposite of a chemical synthesis....
into mullite

Mullite

Mullite, or porcelainite, is a rare clay mineral aluminosilicate. It can form two stoichiometric forms 3Al2O32SiO2 or 2Al2O3SiO2....
and vitreous silica

Fused quartz

Fused quartz and fused silica are types of glass containing primarily silica in amorphous solid form. They are manufactured using several different processes....
via the following reaction: 3(Al₂O₃·SiO₂) ? 3Al₂O₃·2SiO₂ + SiO₂. This transformation results in an expansion.

Uses of kyanite

Kyanite is used primarily in refractory

Refractory

A refractory material is one that retains its strength at high temperatures. ASTM International C71 defines refractories as "non-metallic materials having those chemical and physical properties that made them applicable for structures, or as components of systems, that are exposed to environments above 1000 ?F "....
and ceramic products, including porcelain

Porcelain

Porcelain is a ceramic material made by heating raw materials, generally including clay in the form of kaolin, in a kiln to temperatures between and ....
plumbing fixtures and dishware

Dishware

Dishware is the general term for the dishes used in serving, and eating food, including plate s and bowls. Dinnerware is a synonym, especially meaning a set of dishes, including serving pieces....
. It is also used in electrical insulators and abrasives. Kyanite has been used as a gemstone

Gemstone

A gemstone or gem, also called a precious or semi-precious stone, is a piece of attractive mineral, which — when cut and polished — is used to make jewellery or other adornments....
, though this use is limited by its anisotropism and perfect cleavage. Kyanite is one of the index minerals that are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism. Finally, as with most minerals, kyanite is a collector's mineral.

Associated minerals

Kyanite is usually found in association with its polymorphs, as well as other silicate minerals. These include:

andalusite
Andalusite

Andalusite is an aluminium Silicate minerals mineral with the chemical formula Al2SiO5.The variety chiastolite commonly contains dark inclusions of carbon or clay which form a checker-board pattern when shown in cross-section....
, Al₂SiO₅
sillimanite
Sillimanite

Sillimanite also called Bucholzite is an alumino-silicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman ....
, Al₂SiO₅
quartz
Quartz

Quartz is the most abundant mineral in the Earth's continental crust . It is made up of a Crystal structure of silica tetrahedra. Quartz has a hardness of 7 on the Mohs scale and a density of 2.65 g/cm?....
, SiO₂
staurolite
Staurolite

Staurolite is a red brown to black, mostly opaque, Silicate minerals mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5 and a rather complex chemical formula: 2aluminum94oxygen204....
, Fe₂Al₉Si₄O₂₂(OH)₂
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....
s, AB_2-3(X, Si)₄O₁₀(O,F,OH)₂
garnet
Garnet

The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" comes from the Latin language granatus , possibly a reference to the Punica granatum , a plant with red seeds similar in shape, size, and color to some garnet crystals....
s, A₃B₂(SiO₄)₃

Alternative names

Kyanite has several alternative names, including disthene, munkrudite and cyanite. White-grey kyanite is also called rhaeticite.