Hypersthene

hypersthene

enstatite

ferrosilite

augite

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Hypersthene is a term used for a mineral part way between enstatite and ferrosilite. It is not a valid mineral name.
Formulae:
Hypersthene (Mg,Fe)SiO₃
Enstatite MgSiO₃
Ferrosilite FeSiO₃ Inosilicates (chain silicates)
Properties of hypersthene:
Specific gravity:
Hardness: 5½ to 6
Streak: Greyish white, greenish
Colour: Greyish white
Solubility: Insoluble in water, nitric and sulphuric acid; soluble in hydrochloric acid
Environments:

Metamorphic environments

Hypersthene occurs in igneous rocks and schist and as pyroclasts (particles ejected during a volcanic eruption). It also may be found in basalt.

Alteration

augite and CO₂ to hypersthene, calcite and quartz
Ca(Mg,Fe)Si₂O₆ + CO₂ → (Mg,Fe)SiO₃ + CaCO₃ + SiO₂
(DHZ 2A p384)

hypersthene, augite and Fe and Cr-rich spinel to garnet and olivine
2(Mg,Fe)SiO₃ + Ca(Mg,Fe)Si₂O₆ + (Mg,Fe)(Al,Cr)₂O₄ ⇌ Ca(Mg,Fe)₂(Al,Cr)₂(SiO₄)₃ + (Mg,Fe)₂SiO₄
(DHZ 2A p258)

jadeite, diopside, magnetite and quartz to aegirine, kushiroite (pyroxene) and hypersthene
2NaAlSi₂O₆ + CaMgSi₂O₆ + Fe²⁺Fe³⁺₂O₄ + SiO₂ ⇌ 2NaFe³⁺Si₂O₆ + CaAlAlSiO₆ + MgFeSi₂O₆
Aegirine in blueschist facies rocks may be formed by the above reaction (DHZ 2A 512).

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