The occurrence of detrital diamond and moissanite in the fossil Witwatersrand placers and its implication for the evolution of the ancient continent

Although a rare component, the occurrence of detrital diamonds in Witwatersrand placers has been reported from localities as much as 200 km apart. Brown and green colour spots on the surface of the diamonds as well as associated etched surfaces point to radiation damage during their burial in uraniferous rock. At least two periods of radiation damage are evident. The occurrence of moissanite in kimberlite and its association with diamond has been reported from other deposits. Attempts were made to determine the trace element content of single moissanite grains using PIXE. In contrast to artificial SiC no trace elements could be detected in moissanite from reefs. 4 refs., 1 fig