Uraninite is a
uranium-rich
mineral with a composition that is largely UO
2, but which also contains UO
3 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