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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