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Osumilite-(Mg)

Year of discovery: 1975 (Japan as the first occurence in the World)

Locality list: 10 localities of osumilite-(Mg)

• KMg₂Al₃Si₁₂O₃₀
• (K,Na,Ca)(Mg,Mn)₂(Al,Fe)₃(Si,Al)₁₂O₃₀
• [K⁺][]₂[Mg²⁺₂][Al³⁺₃][(AlSi₅O₁₅)₂]^14-

• Class: Milarite group
• Class: Cyclo-Aluminosilicate (Double ring)
• Radioactive: Very weak

• Mg => Fe: Osumilite

• Fe₂Al₃ => Mg₄Fe => Chayesite

• Color: Brown, Blue
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Habit: Short prismatic

• Cleavage: No
• Hardness: 6.5
• Density: 2.6

• System: Hexagonal
• Group: 6/mmm, P6/mcc
• Lattice: a=10.1, c=14.3

Etymology: Osumi region in Kagoshima prefecture, Japan, address of Sakkabira where this mineral was discovered for the first time.