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Carnotite
Chemical Formula	K2(UO2)2(VO4)2·3H2O
Species	Phosphates
Crystal System	Monoclinic
Mohs Scale	2
Specific Gravity	4.70
Color	Bright yellow to lemon-yellow, may be greenish yellow.
Streak	yellow
Luster	Sub-Vitreous, Resinous, Waxy, Silky, Dull, Earthy
Refractive Index	n = 1.750 n = 1.925 n = 1.950
Diaphaneity	Translucent
Cleavage	Perfecton , perfect, micaceous
Fracture	Micaceous
Crystal Habit：Crusts, earthy masses, foliated and granular aggregates.
Geological Setting：Colorado Plateau type uranium deposits, near playas.

Carnotite is a potassium uranium vanadate radioactive mineral with chemical formula: K₂(UO₂)₂(VO₄)₂·3H₂O. The water content can vary and small amounts of calcium, barium, magnesium, iron, and sodium are often present.

Occurrence

Carnotite is a bright to 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 and also radioactive. It is a secondary vanadium and uranium mineral usually found in sedimentary rocks in arid climates. It is an important ore of uranium in the Colorado Plateau region of the United States where it occurs as disseminations in sandstone and concentrations around petrified logs. Occurs in the U.S. states of Wyoming; Colorado; Arizona; Utah. It also occurs incidentally in Grants, New Mexico and Carbon County, Pennsylvania. It is also reported in Zaire; Morocco; Radium Hill, Australia; and Kazakhstan.

Name and discovery

The mineral was first described in 1899 by French scientists M. M. C. Freidel and E. Cumenge, who identified it in specimens from Roc Creek in Montrose County, Colorado, United States. It is named for Marie Adolphe Carnot (1839 - 1920), French mining engineer and chemist.

Related mineral species

Several related mineral species exist, including: margaritasite ((Cs,K,H₃O)₂(UO₂)(VO₄)₂·H₂O) and tyuyamunite, (Ca(UO₂)₂(VO₄)₂·5-8H₂O).