Uraniferous lodes at Radium Hill occur as shear replacements and infillings along overthrust type fractures developed within a domed anticline (northeast-southwest major axis) in granitised metasediments. At least three major shear zones have developed lodes along part of their length over a zone some 3000 feet long. A typical association of normal and transcurrent faults displace the lodes at intervals, and the latter also cause lode splitting and inhibit ore formation locally. The original shapes of the overthrust shear planes, which exhibit central flattening, possibly in part related to doming influence, have apparently resulted in an arched form of each of the orebodies as seen in horizontal projection, probably due to the overlying block being displaced horizontally towards the north-east. The lode lenses therefore have a north pitch in the north, and a south pitch is anticipated in the south. Greatest lode widths accompany changes in lode strike. Radium Hill is the locus of greatly increased igneous activity, with amphibolitised gabbros of two ages, aplitic microgranites and rare earth pegmatites being restricted to the immediate vicinity. There were several distinct periods of mineralisation, with uranium introduction being last. The uranium mineralisation post-dates the plug amphibolites but pre-datea the microgranites and probably also the dyke amphibolites. The source of the uranium is unknown, but the microgranites are a potential source. The amphibolites seem to offer host conditions, in that uranium values are often concentrated in their vicinity.