Weeksite

Weeksite is a naturally occurring uranium silicate mineral with the chemical formula: K2(UO2)2Si6O15•4(H2O), potassium uranyl silicate. Weeksite has a Mohs hardness of 1-2. It was named for USGS mineralogist Alice Mary Dowse Weeks (1909–1988).[2][3]

Weeksite
General
CategorySilicate mineral
Formula
(repeating unit)		K2(UO2)2Si6O15·4(H2O)
Strunz classification9.AK.30
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupPnnb (no. 52)
Unit cella = 14.26 Å, b = 35.88 Å
c = 14.2 Å; Z = 16
Identification
ColourYellow
Crystal habitOccurs as acicular to elongated bladed crystals, flattened on {010}, also as radiating fibrous clusters and spherulites, pseudotetragonal
CleavageDistinct prismatic
Mohs scale hardness1 - 2
LustreWaxy to silky
StreakYellow
DiaphaneityTransparent to translucent
Specific gravity4.1
Optical propertiesBiaxial (-)
Refractive indexnα = 1.596 nβ = 1.603 nγ = 1.606
Birefringenceδ = 0.010
PleochroismX = colorless; Y = pale yellow-green; Z = yellow-green
2V angleMeasured: 60°
Other characteristics Radioactive greater than 70 Bq/g
References[1][2][3]

Appearance

Weeksite is visually similar to other uranium minerals such as carnotite and zippeite, both being encrustations that form on other rocks (usually sandstones or limestones).

Occurrence

Weeksite was first described in 1960 for an occurrence on Topaz Mountain, Thomas Range, Juab County, Utah.[1]

Weeksite occurs within small "opal" veins within rhyolite and agglomerates, and as encrustations in sandstones and limestones. It occurs associated with opal, chalcedony, calcite, gypsum, fluorite, uraninite, thorogummite, uranophane, boltwoodite, carnotite and margaritasite.[2]

See also

References
  1. "Weeksite mineral information and data". Mindat.org. 2011-06-19. Retrieved 2012-02-10.
  2. Handbook of Mineralogy
  3. Webmineral data for weeksite
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