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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