Humite is a mineral found in the volcanically ejected masses of Vesuvius. It was first described in 1813 and named for Abraham Hume (1749–1838).[5]
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| Humite |
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 Humite specimen, Italy |
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| Category | Nesosilicates |
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| Formula | (Mg,Fe)7(SiO4)3(F,OH)2. |
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| IMA symbol | Hu[1] |
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| Strunz classification | 9.AF.50 |
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| Crystal system | Orthorhombic |
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| Crystal class | Dipyramidal (mmm)
H–M Symbol: (2/m 2/m 2/m) |
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| Space group | Pbnm |
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| Unit cell | a = 10.24, b = 20.72
c = 4.73 [Å]; Z = 4 |
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| Color | White, yellow, dark orange, brown |
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| Cleavage | Poor |
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| Fracture | Uneven to subconchoidal |
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| Tenacity | Brittle |
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| Mohs scale hardness | 6–6.5 |
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| Luster | Vitreous |
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| Streak | White |
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| Diaphaneity | Transparent |
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| Specific gravity | 3.20 – 3.32 |
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| Optical properties | Biaxial (+) |
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| Refractive index | nα =1.607–1.643, nβ=1.619–1.653, nγ=1.639–1.675 |
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| Birefringence | 0.0320 |
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| 2V angle | Calculated = 70–78°, measured = 68–81° |
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| Dispersion | Weak, r > v |
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| References | [2][3][4] |
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