The Calumet and Hecla showings are located south of the Lardeau River, between Poplar and Rapid creeks, in the Slocan Mining Division.
Regionally, the area lies within the Selkirk Mountains of southeastern British Columbia. The occurrence is within the Kootenay Arc, a curving belt of highly deformed metasedimentary and metavolcanic rocks which includes the Upper Proterozoic Horsethief Creek Group, the Upper Proterozoic to Lower Cambrian Hamill Group, the Lower Cambrian Badshot Formation, and the Paleozoic Lardeau and Milford groups. The volcano-sedimentary sequence is intruded by numerous Paleozoic to Mesozoic granitoid plutons.
The Lardeau River area of the Selkirk Mountains is mainly underlain by massive pillow lavas, volcanic breccia and green phyllitic rocks of the Index Formation and by grey-green mica schist of the Broadview Formation. Grey phyllitic rocks and marble of the Milford Group are exposed near the edges of the Mesozoic Mobbs Creek, Rapid Creek and Poplar Creek stocks. All rocks have undergone regional metamorphism to middle or upper greenschist facies. Rocks of the Milford Group have also been affected by thermal metamorphism (Geological Survey of Canada Bulletin 193).
On the Calumet and Hecla property gold occurs with pyrite and minor arsenopyrite in quartz veins cutting a metadiorite dike. The veins occupy a faulted contact zone between the dike and the enclosing micaceous schist. The quartz veins strike northwest and dip slightly to the east. The largest vein is 1 to 2 metres wide and has been exposed in a shallow vertical shaft. An adit driven 80 metres down the hill from the shaft failed to intersect the mineralized vein.
Samples collected in 1914 indicate that gold also occurs within the pyritic micaceous schist hosting the veins. A 1.5-metre wide chip sample of the quartz vein assayed 3.4 grams per tonne gold and 27 grams per tonne silver while a 3.6 metre chip sample of footwall schist assayed 3.4 grams per tonne gold. Gold also occurs in massive sulphide veins less than 5 centimetres wide. Visible gold occurs in massive galena and some specimens were reported to contain as much as 25 per cent gold (Minister of Mines Annual Report 1914).
