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Brookite ( TiO2 )
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Crystal symmetry
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Orthorhombic 2/m 2/m 2/m dipyramidal
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Unit cell
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Z = 8
a = 5.4558 Å
b = 9.1819 Å
c = 5.1429 Å
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Formula mass
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79.88 g[1]
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Color
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Brown, yellowish brown, or black
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Cristal habit
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Tabular and striated, pyramidal or pseudohexagonal
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Crystal system
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Orthorhombic
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Twinning
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On {120}, uncertain
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Cleavage
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Poor on {120}, in traces on {001}
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Mohs Scale hardness
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5 1/2 to 6
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Specific gravity
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4.08 to 4.18
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Optical properties
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Biaxial (+)
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Refractive index
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nα = 2.583
nβ = 2.584
nγ = 2.700
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Birefringence
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∂ = 0.117
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2V angle
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Calculated: 12° to 2°
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