Secondary mineral, Ca(UO2)2(PO4)2.10–12H2O; sp. gr. 3.1; hardness 2.0–2.5; tetragonal; usually bright lemon-yellow to greenish-yellow; yellow streak; vitreous lustre; crystals tabular, square, forming foliated, scaly masses; cleavage perfect, basal; radioactive; fluorescent; occurs with torbernite in the oxidized zone of mineral veins.