Uraninite

Uraninite is a uranium-rich mineral with a composition that is largely UO₂, but which also contains UO₃ and oxides of lead, thorium, and rare earths. The uraninite may occur as black octahedral crystals of high specific gravity (9.0 - 10.63); when in masses of pitch[?]-like lustre it is called pitchblende. All uraninites and pitchblende contain a minute amount of radium; it was in pitchblende from the Jáchymov[?] in Czechoslovakia that Marie Curie discovered radium.

An important occurrence of pitchblende is at Great Bear Lake[?] in the Northwest Territories of Canada, where it is found in large quantities associated with silver.

See also: list of minerals