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Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite , and the presence of kyanite in metamorphic rocks generally indicates metamorphism deep in the Earth's crust .
Eclogite piece from Norway with a garnet (red) and omphacite (greyish-green) groundmass.The sky-blue crystals are kyanite.Minor white quartz is present, presumably from the recrystallization of coesite.
An example is provided by the aluminium silicate minerals, kyanite, andalusite, and sillimanite. All three have the identical composition, Al 2 SiO 5. Kyanite is stable at surface conditions. However, at atmospheric pressure, kyanite transforms to andalusite at a temperature of about 190 °C (374 °F).
Kainite (/ ˈ k aɪ n aɪ t / or / ˈ k eɪ n aɪ t /) [4] (KMg(SO 4)Cl·3H 2 O) is an evaporite mineral in the class of "Sulfates (selenates, etc.) with additional anions, with H 2 O" according to the Nickel–Strunz classification.
The minerals kyanite and sillimanite are polymorphs of andalusite, each occurring under different temperature-pressure regimes and are therefore rarely found together in the same rock. Because of this the three minerals are a useful tool to help identify the pressure-temperature paths of the host rock in which they are found.
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Under this criterion, crystals of kyanite appear upward of several meters from the lithologic change. [ 4 ] By the difference in U-Pb detrital zircon ages, 1.87–2.60 Ga zircons have been reported from the Lesser Himalayan Sequence which is bound above by the Main Central Thrust, and 0.8–1.0 Ga zircons have been reported from the Greater ...
Ultra-high-pressure metamorphism refers to metamorphic processes at pressures high enough to stabilize coesite, the high-pressure polymorph of SiO 2.It is important because the processes that form and exhume ultra-high-pressure (UHP) metamorphic rocks may strongly affect plate tectonics, the composition and evolution of Earth's crust.