Color: Light blue, blue, blue-green Chemical composition: Al2Be3(Si8O18) aluminium beryllium sliciate Mohs’ hardness: 7 ½-8 Transparency: Transparent to opaque Luster: Vitreous Fracture: Conchoidal, uneven, brittle Crystal system: Hexagonal (trigonal); long prisms Cleavage: Imperfect Specific gravity: 2.67-2.71 Refractive index: 1.577-1.583 Dispersion: 0.014 Pleochroism: Definite, nearly colorless-light blue Fluorescence: None Occurrence: Afghanistan, Australia, Brazil, India, Kenya Malagasy [...]

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Color: Pale lavender to deep purple Chemical composition: SiO2 silicon dioxide Moh’s Hardness: 7 Transparency: Transparent Luster: Vitreous Fracture: Conchoidal, very brittle Crystal system: Hexagonal (trigonal) with hexagonal prisms Specific gravity: 2.63-2.65 Streak: White Refractive index: 1.544-1.553 Dispersion: 0.013 Pleochroism: Very weak; violet, gray-violet Fluorescence: Weak; greenish Occurrence: Africa, Brazil, Britain, Canada, India, Malagasy Republic, [...]

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Color: Colorless, pink, red, yellow, brown, green, blue, violet, black, multi-colored Chemical composition: (NaLiCa) (Fe11Mg Mn Al)3 Al8 (OH)4 (BO3)Si6O18) aluminum borate silicate, complicated and changeable composition Mohs’ hardness: 7-7 ½ Transparency: Transparent, opaque Luster: Vitreous Fracture: Uneven, small conchoidal, brittle Crystal system: Hexagonal (trigonal) Cleavage: None Specific gravity: 3.02-3.26 (varies with the color) Streak: [...]

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