Weeksite

Weeksite
General
Category	Silicate mineral
Formula (repeating unit)	K2(UO2)2Si6O15·4(H2O)
Strunz classification	9.AK.30
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m)
Space group	Pnnb (no. 52)
Unit cell	a = 14.26 Å, b = 35.88 Å c = 14.2 Å; Z = 16
Identification
Colour	Yellow
Crystal habit	Occurs as acicular to elongated bladed crystals, flattened on {010}, also as radiating fibrous clusters and spherulites, pseudotetragonal
Cleavage	Distinct prismatic
Mohs scale hardness	1–2
Waxy to silky|re|er}}	Waxy to silky
Streak	Yellow
Diaphaneity	Transparent to translucent
Specific gravity	4.1
Optical properties	Biaxial (−)
Refractive index	nα = 1.596 nβ = 1.603 nγ = 1.606
Birefringence	δ = 0.010
Pleochroism	X = colorless; Y = pale yellow-green; Z = yellow-green
2V angle	Measured: 60°
Other characteristics	Radioactive greater than 70 Bq/g
References	[1][2][3]

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]

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

• Earth:List of minerals
• List of minerals named after people
• Mineral evolution

References

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