Carnotite is a soft, yellow, radioactive mineral (see radioactivity), potassium uranyl vanadate (K₂[UO₂]₂[VO₄]₂.nH₂O), a major ore of uranium and vanadium. It is found in Colorado, Wyoming, South Dakota, Pennsylvania, Siberia, Zaire, and Australia as yellow-green crusts or cavity fillings in sandstone and in fossilized wood. It is finely crystalline (monoclinic), dull or earthy. Relative density 3–5.