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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 .
Andalusite, kyanite, and sillimanite are the principal aluminium silicate minerals. [2] [3] [4] The triple point of the three polymorphs is located at a temperature of 500 °C (932 °F) and a pressure of 0.4 GPa (58,000 psi). These three minerals are commonly used as index minerals in metamorphic rocks.
Kaolinite (/ ˈ k eɪ. ə l ə ˌ n aɪ t,-l ɪ-/ KAY-ə-lə-nyte, -lih-; also called kaolin) [5] [6] [7] is a clay mineral, with the chemical composition Al 2 Si 2 O 5 4.It is a layered silicate mineral, with one tetrahedral sheet of silica (SiO 4) linked through oxygen atoms to one octahedral sheet of alumina (AlO 6).
The other is with the incorporation of water molecules directly into the crystalline structure of a new mineral, [1] as with the hydration of feldspars to clay minerals, garnet to chlorite, or kyanite to muscovite. [citation needed] Mineral hydration is also a process in the regolith that results in conversion of silicate minerals into clay ...
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).
Carnallite minerals are mineral sediments known as evaporites. Evaporites are concentrated by evaporation of seawater. The inflow of water must be below the evaporation or use levels. This creates a prolonged evaporation period. In controlled environment experiments, the halides form when 10%–20% of the original sample of water remains. [14]
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. It is a hydrated potassium-magnesium sulfate-chloride, naturally occurring in irregular granular masses or as ...
The minerals in a metamorphic rock and their age relations can be studied by optical microscopy or scanning electron microscopy of thin sections of the rock. Apart from the metamorphic facies of a rock, a whole terrane can be described by the abbreviations LT, MT, HT, LP, MP, HP (from low, medium or high; pressure or temperature).