A massive variety of uraninite or uranium oxide found in metallic veins. Contains 55–75% UO2, up to 30% UO3, usually a little water, and varying amounts of other elements. Thorium and the rare earths are generally absent.
Properties:
Black color, brownish-black streak, pitchy to dull luster. Mohs hardness 5.5, d 6.5–8.5.
Occurrence:
Canada, Colorado, Europe, Zaire.
Hazard:
Radioactive material.
Use:
Most important ore of uranium, original source of radium.