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Dumortierite (Photo) [abbr. Dum ]

Year of discovery: 1881 (Ducarre's quarry, France), 1935 (Japan)

Locality list: 23 localities of dumortierite

• Al₇BSi₃O₁₈
• (Al,Fe³⁺)₇BSi₃O₁₆(O,OH)₂
• [Al³⁺₇][O₃|BO₃|(SiO₄)₃]^21-

• Class: Dumortierite group < Dumortierite supergroup
• Class: Nesosilicate - Borate - Oxide
• Insoluble in: HCl
• Fluorescence: UV excitation (Gray)

• Al => (Mg,Ti): Magnesiodumortierite

• Color: Blue, Bluish green, Purple
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent-Translucent

• Habit: Acicular, Prismatic

• Cleavage: Good on {100} (1 plane), Indistinct on {110} (2 planes)
• Hardness: 7
• Density: 3.3

• System: Orthorhombic
• Group: mmm, Pnma
• Lattice: a=11.8, b=20.2, c=4.7