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Ferro-anthophyllite [abbr. Fath ]

Year of discovery: 1921 (Tamarack and Custer mine, USA), 1936 (Japan)

Locality list: 8 localities of ferro-anthophyllite

• Fe₇Si₈O₂₂(OH)₂
• [][Fe²⁺₂][Fe²⁺₅][(OH)₂|Si₈O₂₂]^14-

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

• Polymorph: Grunerite (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

• Fe₂Si₂ => Al₄: Ferro-gedrite

• Color: Dark brown
• Streak: White
• Luster: Vitreous
• Diaphaneity: Translucent

• Habit: Acicular, Prismatic

• Cleavage: Distinct on {110} (2 planes, 120 degree)
• Hardness: 5.5-6

• System: Orthorhombic
• Group: mmm, Pnma