Enstatite

Enstatite is a mineral; 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)

Enstatite

Occurrence

Isolated crystals are rare, but orthopyroxene is an essential constituent of various types of igneous rocks and metamorphic rocks. Magnesian orthopyroxene occurs in plutonic rocks such as gabbro (norite) and diorite. It may form small idiomorphic phenocrysts and also groundmass grains in volcanic rocks such as basalt, andesite, and dacite.

Enstatite Gems

Enstatite, close to En₉₀Fs₁₀ in composition, is an essential mineral in typical peridotite and pyroxenite of the Earth's mantle. Xenoliths of peridotite are common in kimberlite and in some basalt. Measurements of the calcium, aluminum, and chromium contents of enstatite in these xenoliths have been crucial in reconstructing the depths from which the xenoliths were plucked by the ascending magmas.

Physical Properties

Physical Properties of Enstatite
Chemical Classification	silicate
Color	grayish white, yellowish, green, brown
Streak	white to gray
Luster	vitreous
Diaphaneity	translucent to opaque
Cleavage	good, prismatic
Mohs Hardness	5.5 to 6
Specific Gravity	3.2 to 4.0
Diagnostic Properties	cleavage, color, luster
Chemical Composition	MgSiO3
Crystal System	orthorhombic
Uses	minor gemstone, decorative purposes

Sources: Wikipedia