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Grunerite [abbr. Gru ]

Year of discovery: 1853 (Sarvengude ravine, France), 1894 (Japan)

Locality list: 18 localities of grunerite

• Fe₇Si₈O₂₂(OH)₂
• [][Fe²⁺₂][Fe²⁺₅][(OH)₂|(Si₄O₁₁)₂]^14-

• Class: Mg-Fe-Mn amphibole subgroup < w(OH,F,Cl)-dominant amphibole group < Amphibole supergroup
• Class: Inosilicate (Double chain) - Hydroxide
• One of minerals called Asbestos.

• Polymorph: Ferro-anthophyllite (Orthorhombic), proto-ferro-anthophyllite (Orthorhombic)

• Fe => Mg: Anthophyllite, Cummingtonite, Proto-anthophyllite

• Fe₂ => Mn₂: Mangano-grunerite, Proto-ferro-suenoite
• Fe₂ => Ca₂: Ferro-actinolite
• Fe₂ => Na₂: Riebeckite

• Color: Brown, Brownish green
• Streak: Colorless
• Luster: Vitreous
• Diaphaneity: Translucent-Opaque

• Habit: Acicular, Prismatic

• Cleavage: Perfect on {110} (2 planes, 120 degree), Distinct (1 plane)
• Hardness: 5-6
• Density: 3.5

• System: Monoclinic
• Group: 2/m, C2/m
• Lattice: a=9.6, b=18.2, c=5.3, β=102.1

Synonym: Amosite