The Golconda occurrence is located 1 kilometre due west of Olalla, British Columbia.
Dan and Archie McEachern first worked the Golconda as early as 1899. By 1931, development consisted of two tunnels, an upper (No. 1) and lower (No. 2) with crosscuts and raises. Samples taken in 1902 yielded 2 to 3 per cent copper (Minister of Mines Annual Report 1902, page 185). Development work with sporadic ore shipments continued until about 1931. The property remained idle until 1946, when purchased by Hedley Monarch Gold Mines Ltd. A small amount of further development work was done on the No. 2 adit. The property lay idle until 1959 when Keremeos Mines Ltd. completed another 61 metres of raising and 15 metres of drifting. A mill was also constructed and 1361 tonnes of ore mined and milled. Friday Mines Ltd. also completed 7 diamond-drill holes. The property closed in 1961. Mollycott Mines Ltd. acquired the Golconda property in 1966 and began underground and mill rehabilitation. A new adit (No. 5) was excavated and some stoping done. Trent Resources Ltd. acquired the Golconda in 1969. They completed 10 diamond-drill holes totalling 1193 metres and mapping of the underground workings. In the following year, some stoping, underground rehabilitation work, and exploration of a new zone were carried out. A new 90.7-tonne per day mill was also constructed but was only operated a short time due to recovery difficulties and insufficient ore feed. In the 1980s and 1990s the property and much of the surrounding area have been explored by Goldcliff Resources Corp.
The Golconda occurrence is located within the ultramafic to alkaline Middle Jurassic Olalla intrusion. This intrusion has intruded a sequence of oceanic sediments and volcanics of the Carboniferous to Triassic Shoemaker and Old Tom formations. Black to green chert, light grey quartzite and minor limestone lenses comprise the dominant lithologies. The Shoemaker and Old Tom formations form a broadly folded, east-dipping sequence in the area. The Olalla intrusion consists of a magnetite-bearing pyroxenite peripheral zone to a diorite and syenite core. The pyroxenite is composed primarily of augite with lesser magnetite. Potassic alteration consisting of biotite, orthoclase, calcite and quartz occurs within the pyroxenite. The syenite is fine grained, light grey to buff to pink and has also been altered to orthoclase and quartz. Coarse grained syenite dikes occur at the contact with the peripheral pyroxenite zone.
Metasomatic deposits have formed along the contact of the Olalla intrusion with Shoemaker sediments. Mineralization is related to skarns, shearing and quartz veining. Mineralization consists mainly of auriferous and argentiferous pyrite and pyrrhotite with minor chalcopyrite, malachite, azurite and tetrahedrite.
The Golconda occurrence consists of a 1.5-metre wide shear zone consisting of one or more slickensided, gouge-filled and en echelon fault planes, cutting pyroxenite. The pyroxenite contact with silicified schist with minor limestone and tuff is marked by a shear. Quartz intermixed with brecciated wallrock and carbonaceous material comprise the gangue of the shear zone, which has an overall strike of 304 degrees and a dip of 68 degrees northeast. A number of quartz lenses occur in the shear zone and appear to be related to open spaces or areas of reduced pressure, marked by changes in attitude of the shear zone. The quartz is crudely banded and hosts pyrite, chalcopyrite, molybdenite and minor galena with anomalous gold and silver values.
Some adits were driven along various sections of the shear zone. Three main levels or adits follow the shear zone. The Nos. 1 and 2 levels were developed by D. MacEachern, possibly as early as 1918. The No. 2 level, at about 738 metres elevation, consists of about 305 metres of crosscutting and drifting, of which about 137 metres is along the shear. Five mineralized lenses were discovered in the No. 2 adit along the shear zone. The size of these lenses were: No. 1 lens (13.7 by 9.1 metres), No. 2 lens (18.3 by 15.2 metres), No. 3 lens (12.2 by 12.2 metres), No. 4 lens (10.7 by 3.6 metres) and No. 5 lens (9.1 by 6.1 metres). A chip sample from the No. 4 lens taken in 1946 yielded 0.34 gram per tonne gold, 37.71 grams per tonne silver, 1.64 per cent copper and 1.12 per cent molybdenum (Minister of Mines Annual Report 1946, page 126). From the No. 5 lens, a 40.6- centimetre chip sample yielded 0.34 gram per tonne gold, 37.71 grams per tonne gold, 9.20 per cent copper and 1.53 per cent molybdenum (Minister of Mines Annual Report 1946, page 126). Two samples from the No. 2 adit in 1927 yielded trace gold, 34.28 to 68.57 grams per tonne silver, 7.0 to 14.1 per cent copper and 0.4 to 1.0 per cent molybdenum (Minister of Mines Annual Report 1927, page 239).
The No. 1 level, at 776 metres elevation and 57.6 metres to the southeast of the No. 2 adit, consists of 68.5 metres of crosscutting and drifting, of which about 43 metres is along the shear. The mineralization is similar and about the same grade as found in the No. 2 adit (Minister of Mines Annual Report 1946, page 126).
Level No. 5 was developed in 1967 by Mollycot Mines Ltd. The portal is at about 654 metres elevation. A total of 387 metres of underground development was carried out with only a small amount along the shear. A number of stopes, ore passes and manways connect the levels.
Diamond drilling has been conducted during three separate companies at different times. In 1961, Friday Mines Ltd. drilled seven drillholes. Then in 1969, Trent Resources drilled 10 drillholes, totalling 1193 metres. The drill results of these two programs are unknown. In 1978, Brenda Mines Ltd. drilled four holes totalling 892 metres. The continuity of the breccia zone was proven at depth but gold values were reported to be low grade (Assessment Report 22882).
A reserve calculation was made on the Golconda occurrence in 1970. Combined (visible, probable and obtainable) ore reserves of 54,248 tonnes were determined, grading 1.64 per cent copper and 0.97 per cent molybdenum (Assessment Report 22882).
Limited production occurred from this property and a small mill that was operated intermittently. In 1917, 1991 kilograms molybdenite were mined from a small lens and shipped to Ottawa where 204 kilograms molybdenum were recovered. A 1.81-tonne shipment of copper ore was also shipped and reported to yield 19 per cent copper (Minister of Mines Annual Report 1917, page 206). In 1918, a 9-tonne shipment of ore to the Trail smelter yielded 18.6 per cent copper and 58.28 grams per tonne silver (Minister of Mines Annual Report 1918, page 213). In 1960, 1361 tonnes of ore were milled and produced 62 grams gold, 14,307 grams silver, 27,696 kilograms copper, 638 kilograms lead and 2456 kilograms molybdenum (Assessment Report 22882). Total recorded production from the Golconda occurrence was 1421 tonnes mined from which 30,200 grams of silver, 218 grams of gold, 38,068 kilograms of copper, 2660 kilograms of molybdenum and 765 kilograms of lead were recovered.