Abstract: Descloizite, cuprian descloizite, and mottramite from most of the known prospects and mines in the Otavi Mountain Land were sampled and subsequently analysed chemically and by X-ray diffraction. Unit cell parameters were refined with the aid of a computer program. It was found that, contrary to previous opinion, chemical parameters of these vanadates can be deduced from their X-ray powder data according to the equations (correlation coefficients in parenthesis):
ZnO = 75.369c−0.119b−31.177a−456.512(0.9634)
Zn2+ = 369.568c + 236.583b − 146.42a − 3726.344 (0.9642)
CuO = − 74.991c + 0.086b + 29.419a + 486.204 (0.9649)
Cu2+ = − 369.568c − 236.583b + 146.420c + 3826.344 (0.9642).