Schoepite

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Schoepite
Schoepite.jpg
General
Category Uranium minerals
Formula
(repeating unit)
(UO2)8O2(OH)12 • 12(H2O)
Strunz classification 04.GA.05
Crystal symmetry Orthorhombic pyramidal
H-M symbol: (mm2)
Space group: P 21ca
Unit cell a = 14.33 Å, b = 16.79 Å, c = 14.73 Å; Z = 4
Identification
Color Amber, lemon- or sulfur yellow
Crystal habit Commonly as tabular equant, to short prismatic crystals; rarely in microcrystalline aggregates
Crystal system Orthorhombic
Cleavage [001] Perfect, [010] indistinct
Tenacity Brittle
Mohs scale hardness 2.5
Luster Adamantine
Streak Yellow
Diaphaneity Transparent to translucent
Specific gravity 4.8
Optical properties Biaxial (-)
Refractive index nα = 1.690 nβ = 1.714 nγ = 1.735
Birefringence δ = 0.045
Pleochroism X = almost colorless; Y = Z = lemon-yellow to golden yellow
2V angle Measured: 89°
Ultraviolet fluorescence Short and long UV = pale green
References [1][2][3]

Schoepite, empirical formula (UO2)8O2(OH)12•12(H2O)[1] 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 (UO3 • nH2O, 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 Zaïre in 1923,[1] several additional localities are known.

Schoepite was named to honor Alfred Schoep (1881–1966), Professor of Mineralogy at the University of Ghent, Belgium.[2]

References[edit]