Schoepite
General
CategoryUranium minerals
Formula
(repeating unit)
(UO2)8O2(OH)12 • 12(H2O)
IMA symbolSho[1]
Strunz classification4.GA.05
Crystal systemOrthorhombic
Crystal classPyramidal (mm2)
H-M symbol: (mm2)
Space groupP21ca
Unit cella = 14.33 Å, b = 16.79 Å
c = 14.73 Å; Z = 4
Identification
ColorAmber, lemon- or sulfur yellow
Crystal habitCommonly as tabular equant, to short prismatic crystals; rarely in microcrystalline aggregates
Cleavage[001] Perfect, [010] indistinct
TenacityBrittle
Mohs scale hardness2.5
LusterAdamantine
StreakYellow
DiaphaneityTransparent to translucent
Specific gravity4.8
Optical propertiesBiaxial (-)
Refractive indexnα = 1.690 nβ = 1.714 nγ = 1.735
Birefringenceδ = 0.045
PleochroismX = almost colorless; Y = Z = lemon-yellow to golden yellow
2V angleMeasured: 89°
Ultraviolet fluorescenceShort and long UV = pale green
Other characteristics Radioactive
References[2][3][4]

Schoepite, empirical formula (UO2)8O2(OH)12•12(H2O)[2] is a rare alteration product of uraninite in hydrothermal uranium deposits. It may also form directly from ianthinite. The mineral presents as a transparent to translucent yellow, lemon yellow, brownish yellow, or amber orthorhombic tabular crystals. Although over 20 other crystal forms have been noted; rarely in microcrystalline aggregates. When exposed to air schoepite converts over a short time to the metaschoepite form (UO3nH2O, n < 2) within a few months of being exposed to ambient air.

The hardness is 2.5, density is 4.8 g/cm3, and it streaks yellow.

It was first described from specimens from Shinkolobwe mine in Belgian Congo in 1923,[2] several additional localities are known.

Schoepite was named to honor Alfred Schoep (1881–1966), Professor of Mineralogy at the University of Ghent, Belgium.[3]

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. 1 2 3 Mindat.org
  3. 1 2 Webmineral data
  4. Handbook of Mineralogy


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