Yellow weeksite crystals from Goanikontes, Namibia (field of view: 5 mm) — Photo: Klaproth · CC BY-SA 4.0
Weeksite
A soft yellow potassium uranyl silicate named for USGS mineralogist Alice Weeks.
Intro adapted from Wikipedia (CC BY-SA).
Weeksite is an IMA-recognized mineral species in the silicate class, with the chemical formula (K)₂(UO₂)₂(Si₅O₁₃)·4H₂O.
It crystallizes in the orthorhombic crystal system (space group Cmmm).
Key properties: Mohs hardness 2; specific gravity 4.1; Waxy to silky luster; refractive index 1.602; optically biaxial.
IMA symbol Wks, IMA status: approved, named in 1960.
Found in “opal" veinlets in rhyolite, agglomerates, sandstones and limestones.
It is found associated with “Opal, " “chalcedony, " calcite, gypsum, fluorite, uraninite, thorogummite, uranophane, boltwoodite, carnotite, margaritasite.
The mineral was named to honor Dr. Mary Alice Dowse Weeks (1909-1988), mineralogist with the U.S. Geological Survey, noted specialist in the mineralogy of uranium and vanadium.