Calcium and magnesium-bearing sabugalite from the Tono uranium deposit, central Japan

Nakata, Masataka*; Sasao, Eiji   ; Komuro, Kosei*

Various secondary uranium minerals yield in oxidized zone near surface. These minerals indicate retardation of uranium in oxidized zone. Calcium and magnesium-bearing sabugalite occurs as aggregations of yellowish platy crystals in veinlets or druses in conglomerate from the oxidized parts of the Tono uranium deposit, Central Japan. X-ray powder diffractometry of this mineral has reflections consistent with previous powder diffraction data of sabugalite. Chemical analysis reveals the chemical composition of the minerals. SEM-EDS mapping shows that the mineral is compositionally uniform with no micron-scale layering. Charge of cations including Ca and Mg in the cation-HO layer is 1.98 being identical to that of autunite group minerals. This suggests that the charge balance in the cation-HO layer of the mineral could be made by the alkaline earth or alkaline elements rather than by hydrogen ions.