Johnston Lake is located approximately 24 km SE of Kingston Lake on the Manitoba border. The area comprises strongly folded pelitic gneiss, psammite/arkose, and calc-silicate rocks, all intruded by leucogranite that is most likely derived from partial melt. Some of the more extensive leucogranite intrusions may have acted as rigid bodies during younger brittle deformation, creating favourable sites along their margins for uranium mineralization.
Conductors in the area are likely associated with graphitic horizons in the pelite-arkose unit. Numerous anomalous lake-sediment geochemical anomalies (up to 31 ppm U) are present in the area which may indicate the presence of subsurface uranium mineralization. These anomalies seem to extend consistently NE-SW along interpreted faults, suggesting the intersection of structures with preferred host lithologies are favourable for uranium mineralization.
Examination of historic assessment reports from the Johnston Lake area determined that a number of uranium-bearing metasedimentary boulders were uncovered during early exploration activities, but it is unclear if these boulder trains were ever examined recently or followed-up in detail to source areas.