The Johnston showing is located 1.2 kilometres east of the Similkameen River and 18.5 kilometres south of Princeton.

The area is underlain by the eastern facies of the Upper Triassic Nicola Group, comprising mafic augite and hornblende porphyritic pyroclastics and flows. These rocks are intruded by diorite and monzonite, locally pyroxenite and gabbro, of the Early Jurassic Copper Mountain and Lost Horse intrusions.

A northeast-striking shear zone cuts diorite of the Copper Mountain stock (Copper Mountain Intrusions), about 100 metres north of andesite, siltstone, breccia and tuff of the Nicola Group. The zone outcrops discontinuously for 140 metres and is 0.9 to 1.5 metres wide.

The shear zone is sparsely mineralized with chalcopyrite on surface. A shaft in the southwestern portion of the shear zone reveals numerous small pegmatite veins cutting gneissic gabbro. Many of the veins are mineralized with chalcopyrite, bornite and magnetite. A selected grab sample from the shaft dump assayed 1.7 per cent copper (Geological Survey of Canada Memoir 171, page 47).