Letlhakane project: case study in complex uranium mineralogy and its geometallurgical implications

Abstract

Uranium mineralisation within the Letlhakane tenement, Botswana, is complex and characterised by three different ores (primary, oxidised and secondary). From a geometallurgical viewpoint, most uranium occurs in coarse grained, and/or highly soluble minerals; favourable characteristics for conventional extractive metallurgical methods. However, there are several factors presenting challenging metallurgical issues including: the presence of refractory ore (<30% of the uranium); the frequent encapsulation of uranium minerals within the first two ore types; minor gypsum and major carbonate present within the secondary ore type; and high clay content throughout, potentially necessitating agglomeration of the ore. An optimised processing flowsheet has been developed involving two distinct flow paths. First, extraction of the secondary uranium ore through agglomeration and an acid heap leach. Second, a beneficiation stage involving fine grinding and radiometric sorting forming a preconcentrate; followed by a strong, two-stage acid agitation leach to extract the uranium from the refractory uranium bearing minerals.