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Stilpnomelane (Photo) [abbr. stp ]

Year of discovery: 1827 (Melchior and Tobias adits, Czech), 1944 (Japan)

Locality list: 183 localities of stilpnomelane

• KFe₈Si₁₂(O,OH)₃₆,nH₂O
• (K,Ca,Na)(Fe²⁺,Mg,Al,Fe³⁺)₈(Si,Al)₁₂(O,OH)₃₆,nH₂O
• [K⁺][Fe²⁺₈][(OH)₆|(Si₂O₅)₆],nH₂O

• Class: 2:1 layer, Island-Tetrahedral < Modulated hydrous < Phyllosilicate subclass < Silicate class
• Class: Phyllosilicate - Hydroxide - Hydrate
• Variety: Ekmanite (+Mn)
• Radioactive: Very weak

• Color: Brown, Black, Dark green
• Streak: Gray
• Luster: Vitreous
• Diaphaneity: Translucent

• Habit: Platy

• Cleavage: Perfect on {001} (1 plane), Imperfect on {010} (1 plane)
• Hardness: 3-4
• Density: 2.9

• System: Triclinic
• Group: (-1), P(-1)
• Lattice: a=21.7, b=21.7, c=17.4, α=124.1, β=95.9, γ=120.0