Natural vanadates

NATURAL VANADATES (EN: vanadates; DE: naturliche Vanadate; FR: vanadates naturels; ES: vanadatos naturales; RU: ванадаты природные) is the group of the minerals, which are representing by themselves the different, according to composition and complexity, salts of the H3(VO4) orthovanadic acid. There are known approximately 50 minerals (basic and hydrous salts), the majority of which are very rare. Among the natural vanadates, they distinguish the simple anhydrous vanadates. There is most known the Bi[VO4] pucherite; the vanadates with the additional anions are the Pb(Zn,Cu)[OH/VO4] descloizite; the simple vanadates with the water of crystallization are the Cu3[VO4]2•3N2O volborthite; the vanadates with the additional anions and water of crystallization are the carnotite, tyuyamunite, and vanadinite. For the natural vanadates, there are characteristical the insular structures with the [VO4]3- tetrahedra, which are connected by the Na1+, K1+, Ca2+, Ba2+, Cu2+, Pb2+, Zn2+, Mn2+, Bi3+, and Al3+ cations. There are observed also the double (V2O7, V2O8) and more complex chained radicals. The natural vanadates crystallize themselves into the hexagonal, rhombic, monoclinic, and triclinic crystal systems. Vanadates form powders, incrustations, thin crusts, and rarely the well-formed crystals. The colouration is predominantly yellow, red, or brownish-red, mainly at the expense of the [VO4]3- anion, and also of the certain cations (for example, the Cu+ provides the vanadates with the green tints). The hardness is 1-4 according to the mineralogical scale. The density is 2500-7000 kilograms per cubic metre. The majority of the natural vanadates are the supergene minerals.

They distinguish the natural vanadates, which have formed themselves within the oxidation zone of the sulfidic deposits (descloizite, cuprodescloizite, vanadinite, pucherite), and within the sedimentary epigenetic deposits (carnotite, tyuyamunite, volborthite, and others). The clusters of the natural vanadates within the oxidation zone of the sulfidic deposits (for example, Kabwe within Africa), and within the certain sedimentary deposits (for example, the Colorado plateau within the USA), has turned out to be possible thanks to the high migration ability of the V compounds. For the ores with the natural vanadates, there is characteristical the concentration of V2O5 of up to 10%, and the comprehensive content of the elements, which permits to extract also Pb, Zn, Cu, U, R, and other elements. However, the reserves of V within these deposits, as a rule, do not exceed several thousand tonnes.