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Ferro-glaucophane [abbr. Fgl ]

Year of discovery: 1957 (Herin mine, Italy), 1980 (Japan)

Locality list: 11 localities of ferro-glaucophane

• Na₂Fe₃Al₂Si₈O₂₂(OH)₂
• [][Na⁺₂][Fe²⁺₃][Al³⁺₂][(OH)₂|(Si₄O₁₁)₂]^14-

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

• Na => Li: Ferro-holmquistite

• Fe => Mg: Glaucophane (Series)

• Al => Fe: Riebeckite

• []Al => NaFe: Ferro-eckermannite

• []Si => NaAl: Ferro-nybøite (Ferro-nyboite)

• Color: Gray-Dark blue
• Streak: Bluish gray
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Cleavage: Perfect on {110} (2 planes, 120 degree)
• Hardness: 5-6
• Density: 3.1

• System: Monoclinic
• Group: 2/m, C2/m
• Lattice: a=9.6, b=17.9, c=5.3, β=103.6