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Bertrandite (Photo)

Year of discovery: 1883 (Barbin quarry, France, and Petit-Port, France), 1967 (Japan)

Locality list: 9 localities of bertrandite

• Be₄Si₂O₇(OH)₂
• [Be²⁺₄][(OH)₂|Si₂O₇]^8-

• Class: Sorosilicate - Hydroxide
• Insoluble in: HCl
• Electrical: Pyroelectric

• Color: Colorless-Yellow
• Streak: White
• Luster: Vitreous
• Diaphaneity: Transparent

• Habit: Thin Platy, Pyramidal

• Cleavage: Perfect on {001} (1 plane), Distinct on {100}, {010}, {110} (4 planes)
• Hardness: 6-7
• Density: 2.6

• System: Orthorhombic
• Group: mm2, Cmc2₁
• Lattice: a=8.7, b=15.3, c=4.6