A monoclinic mineral 2(K₂(UO₂)₂(VO₄)₂.3H₂O) ; bright yellow to lemon- and greenish-yellow; strongly radioactive; commonly occurs mixed with tyuyamunite; widespread in Colorado, Utah, New Mexico, and Arizona; occurs chiefly in crossbedded sandstones of Triassic or Jurassic age, either disseminated or as relatively pure masses around petrified or carbonized vegetal matter. Secondary in origin, having been formed from the action of meteoritic waters on preexisting uranium minerals; a source of uranium and radium.