Synthesis of calcium vanadate minerals and related compounds

Synthesis of natural vanadates shows that most of them are stable in an acid environment. Phase studies of a portion of the system CaO-V₂O₅-H₂O indicate that calcium vanadates are an indicator of environmental pH conditions. Some minerals, such as pascoute, indicate rapid evaporation of vanadite solutions; other minerals, such as hewettite, show that slow evaporation took place. Cursory examination of systems K₂O-UO₂-(NO₃)₂-V₂O₅ and CaO-UO₂(NO₃)₂-V₂O₅, both in aqueous solution, has yielded information on the relationships among carnotite, tyuyamunite, and rauvite.