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Ferrosilite [abbr. Fs ]

Year of discovery: 1935 (World), 1950 (Japan)

Locality list: 9 localities of ferrosilite

• FeSiO₃
• (Fe,Mg,Ca)SiO₃
• [Fe²⁺][SiO₃]^2-
• Ca/(Mg+Fe+Ca)=0-0.05, Fe/(Fe+Mg)=0.5-1.0

• Class: Ca-Mg-Fe pyroxene group < Pyroxene supergroup
• Class: Inosilicate (Single chain)
• Old definition was Fe/(Fe+Mg)=0.9-1.0
• Variety: Fe/(Fe+Mg)=0.7-0.9, Eulite, Orthoeulite
• Variety: Fe/(Fe+Mg)=0.5-0.7, Ferrohypersthene, Orthoferrohypersthene

• Polymorph: Clinoferrosilite (Monoclinic)

• Ca/(Mg+Fe+Ca) > 0.05: Pigeonite

• Fe => Mg: Enstatite (Series), Clinoenstatite, Akimotoite

• Color: Dark brown-Black
• Streak: Pale grayish brown
• Luster: Vitreous
• Diaphaneity: Translucent-Opaque

• Cleavage: Perfect on {210} (2 planes, 90 degree), Parting on {100} and {010}
• Hardness: 5-6
• Density: 4.0

• System: Orthorhombic
• Group: mmm, Pbca
• Lattice: a=18.4, b=9.1, c=5.2

Synonym: Orthoferrosilite, Eulysite