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Forsterite (Photo) [abbr. Fo ]

Year of discovery: 1824 (Monte Somma, Italy), 1889 (Japan)

Locality list: 1,358 localities of forsterite

• Mg₂SiO₄
• [Mg²⁺₂][SiO₄]^4-

• Class: Olivine group
• Class: Nesosilicate
• Soluble in: HCl
• Magnetism: Diamagnetic
• Alter to Lizardite.

• Polymorph: Ringwoodite (Cubic), Wadsleyite (Monoclinic)

• Mg => Zn: Willemite
• Mg => Be: Phenakite
• Mg => Ca: Calcio-olivine
• Mg => Fe: Fayalite (Series)
• Mg => Ni: Liebenbergite
• Mg => Mn: Tephroite (Series)

• Mg₂ => CaMg: Monticellite
• Mg₂ => CaMn: Glaucochroite
• Mg₂ => CaFe: Kirschsteinite
• Mg₂ => LiAl: Eucryptite

• Color: Green, Pale yellow
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Habit: Short prismatic

• Cleavage: Perfect on {010} (1 plane), Imperfect on {100} (1 plane)
• Hardness: 7
• Density: 3.3

• System: Orthorhombic
• Group: mmm, Pbnm
• Lattice: a=4.8, b=10.2, c=6.0

Etymology: J. Forster, Mineralogist