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Enstatite [abbr. En, Hyp, Oen ]

Year of discovery: 1855 (World), 1903 (Japan)

Locality list: 87 localities of enstatite

• MgSiO₃
• (Mg,Fe,Ca)SiO₃
• [Mg²⁺][SiO₃]^2-
• Ca/(Mg+Fe+Ca)=0-0.05, Mg/(Fe+Mg)=0.5-1.0

• Class: Ca-Mg-Fe pyroxene group < Pyroxene supergroup
• Class: Inosilicate (Single chain)
• Old definition was Mg/(Fe+Mg)=0.9-1.0
• Variety: Mg/(Fe+Mg)=0.7-0.9, Bronzite
• Variety: Mg/(Fe+Mg)=0.5-0.7, Hypersthene
• Insoluble in: HCl
• Magnetism: Diamagnetic
• Substitution pseudomorph: Replaced by Talc. (Agalite)
• Substitution pseudomorph: Replaced by Talc or Serpentine. (Bastite)

• Polymorph: Clinoenstatite (Monoclinic, Low pressure)
• Polymorph: Akimotoite (Trigonal, High pressure)

• Ca/(Mg+Fe+Ca) > 0.05: Pigeonite

• Mg => Fe: Ferrosilite (Series), Clinoferrosilite
• Mg => Mn: Kanoite, Donpeacorite

• Si => Ti: Geikielite

• Color: Gray, Green, Brown
• Streak: Gray
• Luster: Vitreous
• Diaphaneity: Translucent-Opaque

• Habit: Acicular, Prismatic

• Cleavage: Perfect on {210} (2 planes, 90 degree), Paring on {100} and {010} (2 planes)
• Hardness: 5-6
• Density: 3.2

• System: Orthorhombic
• Group: mmm, Pbca
• Lattice: a=18.2, b=8.8, c=5.2

Etymology: Enstates (opposed) in Greek as its melting point is very high.

Synonym: Orthoenstatite, Amblystegite, Chladonite, Ficinite, Paulite, Peckhamite, Phastine