Quick facts General, Category ...
| Quartz |
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 Quartz crystal cluster from Tibet |
| General |
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| Category | Oxide mineral |
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| Chemical formula | Silica (silicon dioxide, SiO2) |
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| Strunz classification | 04.DA.05 |
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| Dana classification | 75.01.03.01 |
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| Identification |
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| Color | Colorless through various colors to black |
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| Crystal habit | 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive |
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| Crystal system | α-quartz: trigonal trapezohedral class 3 2; β-quartz: hexagonal 622[1] |
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| Twinning | Common Dauphine law, Brazil law and Japan law |
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| Cleavage | {0110} Indistinct |
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| Fracture | Conchoidal |
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| Tenacity | Brittle |
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| Mohs scale hardness | 7 - lower in impure varieties |
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| Luster | Vitreous - waxy to dull when massive |
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| Streak | White |
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| Diaphaneity | Transparent to nearly opaque |
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| Specific gravity | 2.65; variable 2.59 - 2.63 in impure varieties |
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| Optical properties | Uniaxial (+) |
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| Refractive index | nω = 1.543 - 1.545 nε = 1.552 - 1.554 |
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| Birefringence | +0.009 (B-G interval) |
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| Pleochroism | None |
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| Melting point | 1670 °C (β tridymite) 1713 °C (β cristobalite)[1] |
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| Solubility | 1 ppmmass at 400 °C and 500 lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2[1] |
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| Other characteristics | Piezoelectric, pyroelectric, may be triboluminescent |
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| References | [2][3][4][5] |
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Quartz
