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Pyroxene minerals are named according to the chemical species occupying the X (or M2) site, the Y (or M1) site, and the tetrahedral T site. Cations in Y (M1) site are closely bound to 6 oxygens in octahedral coordination. Cations in the X (M2) site can be coordinated with 6 to 8 oxygen atoms, depending on the cation size.
Purely pyroxene-bearing volcanic rocks are rare, restricted to spinifex-textured sills, lava tubes and thick flows in the Archaean greenstone belts.Here, the pyroxenite lavas are created by in-situ crystallisation and accumulation of pyroxene at the base of a lava flow, creating the distinctive spinifex texture, but also occasionally mesocumulate and orthocumulate segregations.
The pyroxene pallasite grouplet is a subdivision of the pallasite meteorites (stony-irons). [1] The grouplet is named "pyroxene pallasites" because they are the only pallasites that contain pyroxene. The grouplet was proposed in 1995. [2] It currently has only two members: the Vermillion and Yamato 8451 meteorite.
Jadeite is a pyroxene mineral with composition Na Al Si 2 O 6.It is hard (Mohs hardness of about 6.5 to 7.0), very tough, and dense, with a specific gravity of about 3.4.It is found in a wide range of colors, but is most often found in shades of green or white.
Hedenbergite is a part of a pyroxene solid solution chain consisting of diopside and augite, and is the iron rich end member. One of the best indicators that you have located hedenbergite is the radiating prisms with a monoclinic crystal system.
Diopside is a monoclinic pyroxene mineral with composition MgCaSi 2 O 6. It forms complete solid solution series with hedenbergite (FeCaSi 2 O 6) and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class.
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[2] [1] Jadeite is a type of pyroxene, so this reaction is used for clinopyroxene barometry. NaAlS 2 O 6 + SiO 2 NaAlS 3 O 8 {\displaystyle {\ce {NaAlS2O6 + SiO2 -> NaAlS3O8}}} This particular reaction involves a large change in volume between the reactants and the products , so the reaction is very sensitive to pressure changes.