Billietite , Becquerelite Locality: Shinkolobwe Mine (Kasolo Mine), Shinkolobwe , Central area, Katanga Copper Crescent, Katanga (Shaba) , Democratic Republic of Congo (Zaïre) ( Locality at mindat.org ) Size: 1.9 x 1.7 x 1.4 cm. Sharp, gemmy crystals of this extremely rare species, textbook in form, to just under 2mm poke out from protected pockets in this small matrix. The billietite are the orange crystals, easily seen and eye-visible. Becquerelite occurs on this piece as unusually gemmy, transparent yellow crystals underlying the Billietite. TYPE LOCALITY for both species. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Billietite
An uncommon barium uranyl mineral forming clear yellow orthorhombic crystals, named for Belgian crystallographer Valère Billiet.
Intro adapted from Wikipedia (CC BY-SA).
Billietite is an IMA-recognized mineral species in the oxides & hydroxide class, with the chemical formula Ba(UO₂)₆O₄(OH)₆·8H₂O.
It crystallizes in the orthorhombic crystal system (space group Pbn2_1).
Key properties: specific gravity 5.28–5.36; Adamantine luster; optically biaxial.
IMA symbol Bil, grandfathered status — known before the IMA’s founding, named in 1947.
An uncommon alteration product of uraninite.
It is found associated with Uranophane, fourmarierite, metatorbernite, rutherfordine, becquerelite, studtite, soddyite.
The mineral was named to honor Valère Louis Billiet (1903-1945), Belgian crystallographer, University of Ghent, Ghent, Belgium.