thumb|Carnotite from the Happy Jack Mine, [[Moab, Utah]]
Carnotite is a potassium uranium vanadate mineral with chemical formula K<sub>2</sub>(UO<sub>2</sub>)<sub>2</sub>(VO<sub>4</sub>)<sub>2</sub>·3H<sub>2</sub>O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present. It is a major ore of uranium. It is slightly radioactive.
Occurrence
Carnotite is a bright greenish-yellow mineral that occurs typically as crusts and flakes in sandstones. Amounts as low as one percent will color the sandstone a bright yellow. The high uranium content makes carnotite an important uranium ore. It is a secondary vanadium and uranium mineral usually found in sedimentary rocks in arid climates.
In the United States it is an important ore of uranium in the Colorado Plateau region of the United States where it occurs as disseminations in sandstone
Carnotite is reported in Congo (Kinshasa), Morocco, Australia (Radium Hill) and Kazakhstan. It is named for Marie Adolphe Carnot (1839–1920), French mining engineer and chemist.