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Corundum (Photo) [abbr. Crn ]

Year of discovery: 1794 (World), 1892 (Japan)

Locality list: 189 localities of corundum

• Al₂O₃
• α-[Al³⁺₂][O₃]^6-

• Class: Hematite group
• Class: Oxide
• Variety: Sapphire (+Fe or +Ti, Blue)
• Variety: Ruby (+Cr, Red)
• Insoluble in: HCl
• Magnetism: Diamagnetic
• Fluorescence: UV excitation (Yellow-Red)

• Al => Fe: Hematite (α), Maghemite (γ)
• Al => Cr: Eskolaite
• Al => V: Karelianite
• Al => Ti: Tistarite
• Al => Mn: Bixbyite (γ)
• Al => As: Arsenolite, Claudetite
• Al => Sb: Sénarmontite (Senarmontite), Valentinite
• Al => Bi: Bismite, Sphaerobismoite

• Color: Colorless, Gray. Blue, Red
• Streak: White
• Luster: Adamantine
• Diaphaneity: Transparent-Opaque

• Habit: Hexagonal prismatic, Hexagonal platy

• Cleavage: No, Parting on {0001} (1 plane)
• Hardness: 9
• Density: 4.0

• System: Trigonal
• Group: (-3)m, R(-3)c
• Lattice: a=4.8, c=13.0