Uranophane, basic calcium uranyl silicate,
Formula Ca(UO2)2[SiO3(OH)]2.5H2O.

Crystal system: Monoclinic. (crystals are elongated needles up to 10mm)
Hardness: 2.5
Density: 3.8
Colour: Yellow to pale straw yellow.
Streak: Yellowish.


Uranophane is a secondary mineral occurring in the oxydation zones of uranium deposits as an alteration product of uraninite (uranium oxide, UO2). It frequently occurs in association with other secondary uranium minerals such as autunite and torbenite. Fine mineral specimens come from the Shinkolobwe mine, Kasolo, Zaire.

The specimen shown in the picture comes from Margarita Mine, Pena Bianca, Chihuahua, Mexico.

Uranophane from the Margarita Mine, Pena Bianca, Chihuahua, Mexico.