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Eckermannite [abbr. Eck ]

Year of discovery: 1942 (Hpakant-Tawmaw tract, Myanmar), 1997 (Japan)

Locality list: 4 localities of eckermannite

• Na₃Mg₄AlSi₈O₂₂(OH)₂
• Na₃(Mg,Fe)₄AlSi₈O₂₂(OH)₂
• [Na⁺][Na⁺₂][Mg²⁺₄][Al³⁺][(OH)₂|(Si₄O₁₁)₂]^14-

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

• Mg => Fe: Ferro-eckermannite (Series)

• Al => Fe: Magnesio-arfvedsonite
• Al => Mn: Mangani-eckermannite

• NaMg => []Al: Glaucophane

• MgSi => AlAl: Nybøite (Nyboite)

• Color: Dark bluish green, Dark green
• Streak: Bluish green
• Luster: Vitreous
• Diaphaneity: Translucent

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

• System: Monoclinic
• Group: 2/m, C2/m
• Lattice: a=9.8, b=17.8, c=5.3, β=103.7