tyuyamunite, radioactive, yellow, soft, and waxy uranium and vanadium oxide mineral, Ca(UO2)2(VO4)2·5–8H2O. It is considered to be the calcium analogue of carnotite, from which it can be made artificially and reversibly by cation exchange (calcium exchanges places with potassium in carnotite’s molecular structure). Tyuyamunite occurs widely with carnotite in the southwestern United States and in Central Asia. For detailed physical properties, see vanadate mineral (table).