Microcrystalline and acrystalline masuyite (TYPE LOCALITY) here occurs very richly, in unusual concentration in fact, coating sharp crystals of cubic uraninite (to about 1 cm). I could not explain why the normally more common uranium species uraninite is so rare from this locality which produces so many other uranium minerals but an expert told me the following: The fact that Uraninite crystals are rare in Shinkolobwe is in first place that there where very few cavities where the mineral could cristalise.Where cristallisation was possible, the ground water washed the crystals away. Uranium is one of the most mobile elements so weathering is easy.