Enstatite

Enstatite
General
CategoryInosilicate
Formula
(repeating unit)
MgSiO3
IMA symbolEn[1]
Strunz classification9.DA.05
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPbca
Unit cella = 18.23, b = 8.84
c = 5.19 [Å]; Z = 8
Identification
Formula mass100.387 g·mol−1
ColorWhite, grey, green, yellow or brown - colorless in thin section.
Crystal habitPrismatic crystals, commonly lamellar, fibrous, or massive
TwinningSimple and lamellar on [100]
CleavageGood/distinct on [210]
FractureUneven
TenacityBrittle
Mohs scale hardness5 to 6
LusterVitreous, pearly on cleavage
StreakGray
DiaphaneityTranslucent to opaque
Specific gravity3.2–3.3
Optical propertiesBiaxial (+)
Refractive indexnα = 1.650–1.668; nβ = 1.652–1.673; nγ = 1.659–1.679
Birefringenceδ = 0.009–0.011
PleochroismPink to green pleochroism diagnostic for enstatite, pale green to pale orange perpendicular to pink-green axis
2V angle55–90°
References[2][3][4]

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)SiO
3
, 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).

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Handbook of Mineralogy
  3. ^ Mindat
  4. ^ Webmineral data