Enstatite

Chemical Formula: MgSiO₃
Locality: Common worldwide.
Name Origin: From the Greek enstates – “opponent.”

Enstatite is the magnesium endmember of the pyroxene silicate mineral series enstatite (MgSiO₃) – ferrosilite (FeSiO₃). The magnesium rich members of the solid solution series are common rock-forming minerals found in igneous and metamorphic rocks. The intermediate composition, (Mg,Fe)SiO₃, has historically been known as hypersthene, although this name has been formally abandoned and replaced by orthopyroxene. When determined petrographically or chemically the composition is given as relative proportions of enstatite (En) and ferrosilite (Fs) (e.g., En₈₀Fs₂₀).

Physical Properties

Cleavage: {110} Distinct, {010} Distinct
Color: White, Yellowish green, Brown, Greenish white, Gray.
Density: 3.1 – 3.3, Average = 3.2
Diaphaneity: Translucent to opaque
Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals.
Hardness: 5.5 – Knife Blade
Luminescence: Non-fluorescent.
Luster: Vitreous – Pearly
Streak: gray

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