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Magnesio-arfvedsonite [abbr. Marf ]

Year of discovery: 1957 (Hpakant-Tawmaw Tract, Myanmar), 1952 (Japan)

Locality list: 12 localities of magnesio-arfvedsonite

• Na₃Mg₄FeSi₈O₂₂(OH)₂
• [Na⁺][Na⁺₂][Mg²⁺₄][Fe³⁺][(OH)₂|(Si₄O₁₁)₂]^14-

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

• Na => (K,Na): Potassic-magnesio-arfvedsonite

• Na₂ => Ca: Ferri-winchite

• Mg => Fe: Arfvedsonite (Series)
• Mg => Mn: Mangano-arfvedsonite

• Fe => Al: Eckermannite
• Fe => Mn: Mangani-eckermannite

• OH => F: Magnesio-fluoro-arfvedsonite

• NaSi => CaAl: Ferri-katophorite

• Color: Bluish black, Black
• Streak: Dark grayish blue
• Luster: Vitreous
• Diaphaneity: Opaque

• Habit: Acicular, Prismatic

• Cleavage: Perfect on {110} (2 planes, 120 degree)
• Hardness: 5-6
• Density: 3.2

• System: Monoclinic
• Group: 2/m, C2/m
• Lattice: a=9.8, b=17.9, c=5.3, β=105.0