Urninite (uranium ore, pitchblende) Formula: UO2, UO3 + ThO2, CeO2
Mohs scale hardness: 5–6
Specific gravity: 10.63–10.95 (decreases on oxidation)
Uraninite is a major ore of uranium.
In the United States it can be found in the states of Arizona, Colorado, Connecticut, Maine, Utah, New Hampshire, New Mexico, North Carolina and Wyoming.
It also occurs in Canada, Australia, the Czech Republic, Germany, England, Democratic Republic of the Congo, Rwanda and South Africa.
Important source of pitchblende is at Great Bear Lake in the Northwest Territories of Canada, where it is found in large quantities associated with silver.
References
https://en.wikipedia.org
https://www.mtholyoke.edu/courses/mdyar/slides/mins/pages/uraninite.htm
http://www.mindat.org/min-4102.html