Kyanite
General
Category	Mineral
Chemical formula	Al2SiO5 (aluminium silicate)
Identification
Color	Blue; also green, white, grey, black
Crystal habit	Columnar; fibrous
Crystal system	Triclinic
Cleavage	[100] Perfect, [010] Imperfect
Fracture	Brittle
Mohs Scale hardness	4.5-5 parallel to one axis 6.5-7 perpendicular to that axis
Luster	Vitreous; Pearly
Refractive index	1.71 - 1.75
Pleochroism	Trichroic, colorless to pale blue to blue
Streak	White
Specific gravity	3.56 - 3.67
Melting point
Solubility	None
Diaphaneity	Transparent to translucent

Kyanite, whose name derives from the Greek, kyanos, meaning blue, is a typically blue silicate mineral, commonly found in aluminium-rich metamorphic pegmatites and/or sedimentary rock. Kyanite is a diagnostic mineral of the Blueschist Facies of metamorphic rocks. Kyanite (aluminum silicate) [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... General Name, Symbol, Number silicon, Si, 14 Chemical series metalloids Group, Period, Block 14, 3, p Appearance dark gray, bluish tinge Atomic mass 28. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Color is an important part of the visual arts. ... In mineralogy, shape and size give rise to descriptive terms applied to the typical appearance, or habit of crystals. ... In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... For fractures in bones, see Fracture (bone). ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ... For the file system called Lustre, see Lustre (file system) Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... The refractive index of a material is the factor by which the phase velocity of electromagnetic radiation is slowed relative to vacuum. ... Pleochroism is an optical phenomenon where due to double refraction of light by a colored gem or crystal, the light is divided into two paths which are polarized at a 90° angle to each other. ... The term streak is used in several ways: Streaking, the act of running around nude in public places. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... The melting point of a solid is the temperature at which it changes state from solid to liquid. ... A substance is soluble in a fluid if it dissolves in that fluid. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ... This article is about minerals in the geologic sense; for nutrient minerals see dietary mineral; for the band see Mineral (band). ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... 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. ... Two types of sedimentary rock: limey shale overlaid by limestone. ... Blueschist is a rock that forms by the metamorphism of sodium-rich basic rocks at high pressures and low temperatures, approximately corresponding to a depth of 15 to 30 kilometers and 200 to ~500 degrees Celsius. ... 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. ...

Kyanite is a member of the aluminosilicate series, which includes the polymorph andalusite and the polymorph sillimanite. Kyanite is strongly anisotropic, in that its hardness 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. In general, a polymorph is something that can exist in several states or forms. ... Andalusite-cordierite schist (Large brown crystals are Andalusite Andalusite is an alumino-silicate mineral with the chemical formula Al2SiO5. ... Sillimanite: Biotite gneiss (Mesozoic and Paleozoic) Sillimanite is an alumino-sillicate mineral with the chemical formula Al2SiO5. ... Look up Anisotropy in Wiktionary, the free dictionary Anisotropy (the opposite of isotropy) is the property of being directionally dependent. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer. ...

Uses of kyanite

Kyanite is used primarily in refractory and ceramic products, including porcelain plumbing fixtures and dinnerware. It is also used in electrical insulators and abrasives. Kyanite is important enough an ore that a mining company, the Kyanite Mining Corporation focuses on its processing and refinement. Kyanite has also been used as a gemstone, though this use is limited by its anisotropism and perfect cleavage. 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, Al₂SiO₅
• sillimanite, Al₂SiO₅
• quartz, SiO₂
• staurolite, Fe₂Al₉Si₄O₂₂(OH)₂
• micas, AB_2-3(X, Si)₄O₁₀(O,F,OH)₂
• garnets, A₃B₂(SiO₄)₃

Andalusite-cordierite schist (Large brown crystals are Andalusite Andalusite is an alumino-silicate mineral with the chemical formula Al2SiO5. ... Sillimanite: Biotite gneiss (Mesozoic and Paleozoic) Sillimanite is an alumino-sillicate mineral with the chemical formula Al2SiO5. ... Quartz is the most abundant mineral in the Earths continental crust. ... Staurolite Staurolite is a red brown to black mostly opaque nesosilicate mineral with a white streak. ... rock with mica Mica sheet mica flakes The mica group of minerals includes several closely related materials having highly perfect basal cleavage. ... The garnet group of minerals show crystals with a habit of rhombic dodecahedrons and trapezohedrons. ...

Alternative names

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

Notes for identification

Kyanite's elongated, columnar crystals are usually a good first indication of the mineral, as well as its color (when the specimen is blue). Associated minerals are useful as well, especially the presence of the polymorphs or staurolite, which occur frequently with kyanite. However, the most useful characteristic in identifying kyanite is its anisotropism. If one suspects a specimen to be kyanite, verifying that it has two distinctly different hardnesses on perpendicular axes is a key to identification.

References

• WebMineral Listing
• MinDat Listing
• Mineral Galleries
• Kyanite Mining Corporation
• Mineral Use Notes (Emporia State)