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Roscoelite (Photo)

Year of discovery: 1876 (Stuckslager mine, USA), 1962 (Japan)

Locality list: 4 localities of roscoelite

• KV₂AlSi₃O₁₀(OH)₂
• K(V,Al)₂AlSi₃O₁₀(OH)₂
• [K⁺][V³⁺₂][(OH)₂|AlSi₃O₁₀]^7-

• Class: Dioctahedral < True mica group < Mica supergroup
• Class: Phyllo-Aluminosilicate - Hydroxide
• Soluble in: HCl (Slightly), HNO₃ (Slightly), H₂SO₄ (Slightly)
• Radioactive: Very weak

• K => Ba: Chernykhite

• V => Al: Muscovite
• V => Fe: Glauconite series
• V => Cr: Chromphyllite

• Color: Dark green, Brown, Black
• Streak: Pale green
• Luster: Pearly
• Diaphaneity: Transparent-Translucent

• Habit: Hexagonal Platy

• Cleavage: Perfect on {001} (1 plane)
• Hardness: 2.5
• Density: 2.9

• System: Monoclinic (1M, 2M₁) (Layer-stacking polytype)
• Group: 2/m, C2/c
• Lattice: a=5.3, b=9.1, c=10.3, β=101.0