In recent discussions on the origin of the mineralization of the Witwatersrand and of Blind River, various departures from actualistic principles have been postulated by geologists of the placerist school in necessary support of their views. None of these hypotheses stands up to critical examination; and from consideration of the mineralogy and geochemistry of the banket reefs it is concluded that the mineralization is certainly not of alluvial origin. Claims that detrital uraninite can be recognized in mineragraphic studies lack due objectivity. Because of reworking of the uranium and the probable presence of old radiogenic lead, it is not yet possible to place any reliance on the apparent ages recorded for these banket ores. In speculation on the source of the pay-metals, it is suggested that the mineralization may be linked to periods of granitization late in the history of the Witwatersrand and Huronian geosynclines.