IN a recent paper1 we reported on semiconductivity in CoSb2-type compounds. The ternary analogues of these polycompounds are formed by the arsenopyrite group. The monoclinic minerals arsenopyrite, FeAsS, and gud-mundite, FeSbS, closely correspond to the mineral safflorite, CoAs2. They have the same number of valence electrons and we therefore expect their cations to have the same d-electron configuration. In CoAs2 we have found a magneton number much smaller than that corresponding to one unpaired spin1. A measurement of the magnetic susceptibility of a natural arsenopyrite crystal (from Altenberg, Silesia, the same on which resistivity measurements were performed earlier2) of unknown purity showed a very similar behaviour (see Table 1).