Clinoenstatite

clinoenstatite

diopside

spinel

forsterite

Images

Formula: Mg₂Si₂O₆
Inosilicate (chain silicate), single chains, clinopyroxene subgroup, pyroxene group, monoclinic paramorph of trigonal akimotoite, orthorhombic bridgmanite and orthorhombic enstatite
Crystal System: Monoclinic
Specific gravity: 3.210 calculated
Hardness: 5 to 6
Streak: White
Colour: Colourless, greenish yellow, yellowish brown, green-brown
Solubility: Insoluble in water, hydrochloric, nitric and sulphuric acid
Common impurities: Ti,Al,Cr,Fe,Mn,Ca,Na
Environments:

Plutonic igneous environments
Metamorphic environments

Clinoenstatite occurs as phenocrysts, likely inverted from "protoenstatite," in high-magnesium, non-feldspathic andesites. Exsolved in diopside in ultramafic rocks and in enstatite in high-grade metamorphic hornfelses. An essential constituent of chondrite and achondrite meteorites, likely formed by stress. Associated minerals include diopside, enstatite, chromite, "hypersthene" and glass (HOM).

Alteration

forsterite and anorthite to clinoenstatite, diopside and spinel
2Mg₂SiO₄ + CaAl₂Si₂O₈ ⇌ 2MgSiO₃ + CaMgSi₂O₆ + MgAl₂O₄
The reaction can proceed in either direction, depending on the ambient conditions.

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