Humite

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).[4]

Humite
Humite specimen, Italy
General
CategoryNesosilicates
Formula
(repeating unit)
(Mg,Fe)7(SiO4)3(F,OH)2.
Strunz classification9.AF.50
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H–M Symbol: (2/m 2/m 2/m)
Space groupPbnm
Unit cella = 10.24, b = 20.72
c = 4.73 [Å]; Z = 4
Identification
ColorWhite, yellow, dark orange, brown
CleavagePoor
FractureUneven to subconchoidal
TenacityBrittle
Mohs scale hardness6-6.5
LusterVitreous
StreakWhite
DiaphaneityTransparent
Specific gravity3.20 – 3.32
Optical propertiesBiaxial (+)
Refractive indexnα =1.607-1.643, nβ=1.619-1.653, nγ=1.639-1.675
Birefringence0.0320
2V angleCalculated = 70-78°, measured = 68-81°
DispersionWeak, r > v
References[1][2][3]

See also

References

  1. Handbook of Mineralogy
  2. Webmineral data
  3. Mindat w/ locations
  4. Deer, W.; Howie, R.; Zussman, J. (1997). Rock-forming Minerals: Volume 1A, Second Edition, Orthosilicates. Bath, UK: The Geological Society. ISBN 1-897799-88-8.

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