The Duncan (No. 1) zone is located at 790 metres elevation above sea level on the north side of Glacier Creek, east of Duncan Lake in the Slocan Mining Division.

Regionally, the area lies within the Kootenay Arc near the margins of the Ancestral North American Terrane. The Kootenay Arc is a curving belt of highly deformed metasedimentary and metavolcanic rocks which includes the Upper Proterozoic Horsethief Creek Group, the Eocambrian Hamill Group, the Lower Cambrian Badshot Formation, and the lower Paleozoic Lardeau Group. The volcano-sedimentary sequence is intruded by numerous Ordovician, Devonian and Mississippian granitoid plutons. The rocks have undergone regional metamorphism to middle or upper greenschist facies (Paper 1993-1).

The No. 1 zone is in grey, massive, banded or flecked marble of the Lower Cambrian Badshot Formation which overlies the Hamill Group. The Badshot Formation is characterized by cliff-forming, white to medium grey, commonly laminated marble or dolomitic marble. The marble horizons are tens of metres thick and usually separated by grey, locally calcareous schist. The marble is overlain by a thick succession of fine grained, dark grey and green schists of the Index Formation (Lardeau Group).

The mineralization consists of fine to medium-grained pyrite, sphalerite and galena in bands, lenses and locally irregular veins of white calcite. The calcite is coarse grained and associated with coarse crystalline sphalerite and pyrite deposited in vein cavities.

In 1952, an adit exposed the No. 1 zone for a distance of 70 metres along strike. Within the workings, the zone, up to 3 metres wide, dips steeply to the east and plunges at low angles to the north. Average grade over the entire length of the zone is 2.46 per cent lead and 6.36 per cent zinc for an average width of 1.1 metres (Berens River Mines Annual Report, 1952).