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Alleghanyite

Year of discovery: 1932 (Bald Knob deposit, USA), 1938 (Japan)

Locality list: 91 localities of alleghanyite

• Mn₅Si₂O₈(OH)₂
• (Mn,Mg,Ca)₅Si₂O₈(OH)₂
• Mn²⁺₅[(OH)₂|(SiO₄)₂]^10-

• Class: Humite group
• Class: Nesosilicate - Hydroxide

• Polymorph: Ribbeite (Orthorhombic)

• Mn => Ca: Reinhardbraunsite
• Mn => Mg: Hydroxylchondrodite

• Color: Pale brown
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Aggregate: Massive aggregate of fine crystals

• Cleavage: No
• Hardness: 5.5
• Density: 3.6

• System: Monoclinic
• Group: 2/m, P2₁/a
• Lattice: a=8.3, b=4.9, c=10.7, β=104.6