Sulphatising roasting of a Greenlandic uranium ore, reactivity of minerals and recovery

Uranium in the lujavrite ore from Kvanefjeld, South Greenland, can be solubilised by sulphatising roasting at 700 °C. The reactivity of various lujavrite minerals in the roasting process and the mechanism of the reaction were investigated by X-ray diffraction, optical microscopy, electron microprobe, thermal analysis, Mossbauer and infrared spectroscopy.

Soluble sulphates are formed on the surface of the grains; an outer zone of the grains is transformed; usually a core remains unchanged. Variations in uranium recovery can be explained by variations in the contents of the uranium-bearing minerals, steenstrupine and uranium-containing pigmentary material (altered Zr containing silicate minerals), and in the degree of alteration of steenstrupine.

Characterization of these minerals required many qualitative and a few quantitative electron microprobe analyses.