The Keystone mine is located on the west side of the Coldwater River, approximately 6 kilometres north of the Coquihalla Lakes.

The geology of the upper Coldwater River area is characterized by Late Triassic Nicola Group metavolcanic and metasedimentary rocks derived from the emplacement of plutonic rocks assigned to the Late Jurassic and Early Cretaceous Eagle Plutonic Complex to the west. Along the Coldwater River, the Nicola Group comprises amphibolite, foliated diorite, mylonite and chlorite schist with minor marble in contact with gneissic granodiorite. A dioritic stock of Early Tertiary age has intruded these plutonic rocks west of this contact.

The Keystone mine is situated near the centre of the Early Tertiary quartz diorite (Keystone) stock, which has been estimated to be approximately 1300 by 2200 metres. The southern half of the stock is brecciated, as is the older granodiorite adjacent to it. The brecciation has been attributed to the subsequent emplacement of small stocks and dykes of porphyritic rhyolite. This event was apparently accompanied by pervasive alteration and the introduction of metallic mineralization.

In the area of the mine, rhodochrosite, sphalerite and hematite with galena and minor chalcopyrite and magnetite occur with or without quartz(-carbonate) as veins, veinlets and stringers in shears and brecciated zones. Erratically distributed gold and silver values reportedly occur with the quartz.

The dominant structure hosting this mineralization is a steeply dipping, north-northeast striking shear zone expressed, on the surface, by conspicuous rock alteration and manganese staining. This shear extends from the Stonewall adit (092HNW034)/Julie zone (092HNW023) on Mine Creek northeast past the Keystone mine, and attains widths in excess of 150 metres (diamond-drill hole 80-W2).

Three "vein zones" are known to be hosted along the structure. The No. 1 Vein zone, developed from two levels at the Keystone Mine, comprises quartz, calcite and rhodochrosite with pyrite, sphalerite, galena and rare tetrahedrite. It averages from 5 to 10 centimetres wide, but pinches and swells from a one-centimetre wide pyrite-gouge clay zone to a 30-centimetre wide massive pyrite-quartz vein with minor base metals. It also splits and branches where exposed on the lower level of the mine. A total strike length of approximately 275 metres has been explored, both in underground workings and drill holes.

In 1972, underground sampling of the main fissure zone yielded from 0.15 per cent copper, 0.96 per cent lead, 10.0 per cent zinc, 236.7 grams per tonne silver and 6.2 grams per tonne gold over 0.9 metre (sample 2584) to 0.01 per cent copper, 0.09 per cent lead, 0.20 per cent zinc and 46.9 grams per tonne silver over 10.5 metres (sample 2582; Assessment Report 4174).

In 1978, a sample (K23-6) from the Keystone vein extension in the area of the Anaconda trenches to the northeast of the Keystone adit yielded 0.074 per cent copper, 0.052 per cent lead, 0.077 per cent zinc and 57.5 grams per tonne silver (Assessment Report 7135).

In 1979, a drillhole (W-79-1), located northeast of the Keystone and immediately southeast of Anaconda trenches, intercepted a quartz diorite with quartz-pyrite-sericite-potassium feldspar-molybdenite stockworks and sporadic quartz-sphalerite-galea±rhodochrosite±chalcopyrite veins. The quartz-molybdenite veins average 10 centimetres in width but vary up to 15 centimetres in width and average 1 per 2 metres. Assays of the drillcore yielded an average of 0.233 per cent zinc with 3.5 grams per tonne silver over 265 metres (977 to 1240 metres down hole) and 0.044 per cent molybdenum over 308 metres (1050 to 1358 metres down hole) with several 3 metre sections yielding up to 0.133 per cent molybdenum (Assessment Report 7771).

In 1980, drillhole W-80-1, located north-northeast of the Keystone adit and immediately northwest of the Anaconda trenches, intercepted a clay-sericite–altered granodiorite hosting quartz veins with semi-massive sphalerite and galena yielding 12.05 and unknown per cent lead, 21.55 and unknown per cent zinc, 2223 and 41.0 grams per tonne silver with 0.2 and 23.2 grams per tonne gold over 0.6 and 3.0 metres (255.8 to 256.4 and 317.0 to 327.0 metres down hole), respectively, whereas a drillhole (W-80-2) located on the former Anaconda trenches yielded 0.29 per cent zinc over 41.7 metres (698.4 to 740.1 metres down hole; Assessment Report 8863).

In 1981, detailed sampling of the vein produced erratic precious metal values. Silver values have ranged from better than 35 to greater than 754 grams per tonne (Assessment Report 18485). Gold values have been generally low. The best assay from the upper level has been 29.5 grams per tonne gold and 576.0 grams per tonne silver across a ‘very narrow’ hangingwall vein (Assessment Report 18485). Values up to 5.07 grams per tonne gold and 275.7 grams per tonne silver have been obtained from samples from the lower level (Assessment Report 18485).

In 2005, a 0.1- by 0.4-metre chip sample (B159147) from a brecciated zone located north of the lower Keystone adit assayed 0.193 per cent zinc and 23.4 grams per tonne silver (Assessment Report 28410).

In 2006, chip samples (5239 through 5241) from a cleared area exposing narrow (0.01 to 0.10 metres wide) quartz fractures with galena, located approximately 100 metres northeast of the lower Keystone adit, yielded from 17.4 grams per tonne silver over 1.2 metres to 0.16 gram per tonne gold, 88.1 grams per tonne silver and 0.186 per cent zinc over 0.1 metre (Assessment Report 30578).

In 2017, a rock sample (CRK001), taken north of the Keystone adit assayed 76.8 grams per tonne silver, 0.500 per cent lead and 0.123 per cent zinc (Assessment Report 36976). The following year, a rock sample (ARK18-001), taken from the same area as the previous years sample, assayed 0.92 gram per tonne gold, 86.2 grams per tonne silver and 0.500 per cent lead (Assessment Report 37926).

Work History

Base and precious metal mineralization were originally discovered at this locality in the early 1900s and underground development had taken place by 1936. During 1936 through 1951, sporadic exploration consisting of at least three short adits and numerous trenches being developed on the area. During the 1950s, extensive underground development was completed. The only production from the mine occurred in 1955, when 81 tonnes of ore were shipped for processing (Minister of Mines Annual Report 1955, page A48). By this time, the main Keystone workings are reported to comprise two adits with crosscuts, a raise to the surface and approximately 219 metres of drifting on two levels on the No. 1 vein zone.

In 1965 and 1966, Anaconda American Brass Ltd. and Dorian Mines Ltd. held the area. Dorian Mines is reported to have completed approximately 1500 metres of trenching and 32 diamond drill holes, totalling 2018 metres, to the south of Dry (Mine) Creek (MINFILE 092HNW023 and 092HNW022), whereas Anaconda completed programs of trenching, geophysical and geochemical surveys north of Dry (Mine) Creek and northeast of the Keystone adit. In 1969, Noranda optioned several claims south of Mine Creek and completed six drillholes, totalling 911 metres.

In 1971, Corval Resources completed a program of geological mapping and soil sampling on the area as the Dry property. The following year, a program of geological mapping, minor rock sampling, a 9.6 line-kilometre induced polarization survey and a 13.4 line-kilometre ground magnetic survey were completed on the property.

In 1973, Denison Mines Ltd. completed a 12.8 line-kilometre induced polarization survey on the Dry Creek property. Later reports, in 1978, indicated that Denison Mines and Noranda also completed four and seven diamond drill holes, respectively, at this time. Also at this time, El Paso Mining and Milling Co. completed a program of geological mapping and soil sampling on the area immediately north as the What (MINFILE 092HNW050) claims.

During 1977 through 1980, Western Mines Ltd. completed programs of geological mapping, geochemical (rock, silt and soil) sampling, trenching, a 15.0 line-kilometre induced polarization survey and six diamond drill holes, totalling 4954 metres, on the area as the Rover and Keystone properties.

In 1981, Westmin Resources Ltd. completed a program of geological mapping, geochemical (rock and soil) sampling, trenching and eight diamond drill holes, totalling 664 metres, on the Keystone property. The diamond drilling and trenching was performed in the areas of the Keystone and Julie (MINFILE 092HNW023) occurrences.

In 1986, Blue Gold Resources acquired the Keystone property and through 1990 completed programs of geochemical (rock and soil) sampling, ground electromagnetic and magnetic surveys and four diamond drill holes, totalling 404.4 metres, on the property. Drilling was performed on the Keystone and Julie (MINFILE 092HNW023) occurrences.

During 2005 through 2008, the area was prospected, and soil and rock sampled by Bryan Livgard as the Silver Mountain property.

During 2016 through 2019, Cazador Resources Ltd. completed minor programs of geological mapping and rock and soil sampling on the Keystone property.