The Union occurrence is plotted at an elevation of approximately 1080 metres on an east-facing slope, approximately 1200 metres west of Loon Lake.

Regionally, the area is underlain by hornblende schists, limestone and banded quartzite of the Upper Mississippian to Permian Milford Formation and basaltic volcanic rocks of the Carboniferous to Permian Kaslo Group. Granodioritic intrusive rocks of the Middle Jurassic Nelson Batholith are exposed to the west.

The occurrence is hosted in limestone and schist of the Mississippian to Permian Milford Formation. Galena and minor sphalerite occur locally in gossanous patches in limestone striking north with a dip of 40 degrees west. Approximately 45 to 60 metres south of the shaft trenches have exposed a fault striking north 20 degrees west and dipping 60 degrees south. Rubble beside the trench is reported to host galena and minor sphalerite mineralization. Another zone of mineralization is exposed in a trench, approximately 20 metres north of the shaft, and is composed of a rusty zone containing minor galena at the contact of limestone and dark-grey schist.

In 1980, diamond drilling yielded intercepts of up to 0.23 per cent lead, 1.76 per cent zinc and 8.9 grams per tonne silver over 0.4 metre (63.2 to 63.6 metres down hole) of calcite veining hosting sphalerite and galena in a limestone in hole 80-14 (Assessment Report 8992).

In 2014, two chip samples (1444305 to 1444306) of oxidized galena from the occurrence area yielded 18.53 and 38.65 per cent zinc, 2.10 and 4.21 per cent lead with 48 and 56 grams per tonne silver, respectively (Assessment Report 35075).

Work History

In 1890, an inclined shaft was developed to a depth of 25.9 metres.

In 1979 and 1980, David Minerals Ltd. conducted programs of geochemical (soil and silt) sampling, a ground VLF-EM survey and three diamond drill holes, totalling 422.41 metres, on the area as the Union 2-3, Alf and Broken Hill claims. In 1989, South Kootenay Goldfields Inc., on behalf of Dragoon Resources Ltd., conducted a program of prospecting, geological mapping and rock sampling on the area as the Peanut Butter property.

During 2007 through 2011, Goldcliff Resource Corp. completed programs of prospecting, geological mapping, geochemical (rock, silt and soil) sampling and an airborne geophysical survey on the regionally extensive Ainsworth Silver property. In 2012 and 2014, David Wallach prospected and rock sampled the area as the Ainsworth property. In 2015, Goldcliff Resource Corp. conducted a program of prospecting, geological mapping, geochemical (rock, silt and soil) sampling and a 4.1 line-kilometre ground electromagnetic survey on the area as part of the Ainsworth Silver property.

In 2020 and 2021, Goldcliff Resource Corp. conducted a further program of geochemical (rock, silt and soil) sampling and a 508.0 line-kilometre airborne magnetic, electromagnetic and radiometric survey on the Ainsworth Silver property.