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Eggletonite

Year of discovery: 1984 (Big Rock quarry (3M quarry, Arch Street Pike quarry), USA), 2000 (Japan)

Locality list: A locality of eggletonite

• Na₂Mn₈AlSi₁₁O₂₉(OH)₇,11H₂O
• (Na,K,Ca)₂(Mn,Fe)₈(Si,Al)₁₂O₂₉(OH)₇,11H₂O
• [Na⁺₂][Mn²⁺₈][(OH)₇|AlSi₁₁O₂₉]^18-,11H₂O

• Class: 2:1 layer, Strip-Tetrahedral < Modulated hydrous < Phyllosilicate subclass < Silicate class
• Class: Phyllo-Aluminosilicate - Hydroxide

• Na => K: Ganophyllite

• Na₂ => Ca: Tamaite

• Color: Brown
• Streak: Pale brown
• Luster: Vitreous
• Diaphaneity: Translucent

• Cleavage: Perfect on {001} (1 plane)
• Hardness: 3-4
• Density: 2.8

• System: Monoclinic
• Group: m, Ia
• Lattice: a=5.6, b=13.7, c=25.0, β=94.0