billietite

{{Infobox mineral | name = Billietite | image = Becquerelite-Billietite-rad08-04c.jpg | imagesize = 260px | alt = | caption = Becquerelite (yellow) and billietite (orange) | category = Oxide minerals | formula = Ba(UO2)6O4(OH)6•8H2O | IMAsymbol=Bil | molweight = | strunz = 4.GB.10 | dana = 5.7.1.3 | system = Orthorhombic | class = Pyramidal (mm2) (same H-M symbol) | symmetry = Pbn21 | unit cell = | color = Yellow to golden-yellow, amber-yellow, orange-yellow | colour = | habit = | twinning = | cleavage = Perfect on {001}, imperfect on {110} and {010} | fracture = | tenacity = Brittle | mohs = | luster = Adamantine | streak = | diaphaneity = Transparent, translucent | gravity = | density = 5.28 - 5.36 g/cm3 | polish = | opticalprop = | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = 25px Radioactive | prop1 = | prop1text = | references = }}

Billietite is an uncommon mineral of uranium that contains barium. It has the chemical formula: Ba(UO2)6O4(OH)6•8H2O. It usually occurs as clear yellow orthorhombic crystals. Billietite is named after Valere Louis Billiet (1903–1945), Belgian crystallographer at the University of Ghent, Ghent, Belgium.