NATURAL AND SYNTHETIC SELENITES AND SELENATES AND THEIR GLADSTONE-DALE COMPATIBILITY

The oxysalts of the element selenium, selenites (with Se4+) and selena tes (with Se6+) are relatively Tare as minerals. Only fifteen selenium oxysalts are known to occur naturally; thirteen are ''pure'' selenite s, i.e., they contain only selenite anionic groups. The other two mine rals each contains two anionic groups; in one case, selenate and sulfa te, and in the other, selenate and selenite. The selenites are: ahlfel dite, NiSeO3.2H2O; chalcomenite and clinochalcomenite, CuSeO3.2H2O; co baltomenite, CoSeO3.2H2O; demesmaekerite, Pb2Cu5(UO2)2(SeO3)6 (OH)6.2H 2O; derriksite, Cu4(UO2)(SeO3)2(OH)6; francisite, Cu3Bi(SeO3)2O2Cl; gu illeminite, Ba(UO2)3(SeO3)2(OH)4.3H2O; haynesite, (UO2)3(OH)2(SeO3)2.5 H2O; mandarinoite, Fe2(SeO3)3.6H2O; marthozite, CU(UO2)3(SeO3)3(OH)2.7 H2O; molybdomenite, PbSeO3; and sophiite, Zn2(SeO3)Cl2. The selenates are: olsacherite, Pb2(SeO4)(SO4) and schmiederite, Pb2Cu2(OH)4(SeO4)(S eO3). In addition, the poorly described ''kerstenite'' is mentioned in many references and may be PbSeO4, another selenate. The Gladstone-Da le equations were applied to the selenites and selenates to determine the compatibility of the optical data, calculated densities and chemic al compositions. Calculations could not be carried out for francisite because optical data are not available, but the distribution among the compatibility categories of the other selenium oxysalts is: superior 7, excellent 4, good 2, fair 0 and poor 1. The compatibility distribut ion for five synthetic selenates is: superior 2, excellent 2, good 0, fair 1 and poor 0. The data for the only synthetic selenite fell into the superior category. On the basis of the compatibility results, a re study of marthozite is recommended. In addition, the minimally describ ed ''kerstenite'' should be properly characterized.