The Collins Gulch deposit is exposed in outcrop and various surface and underground workings for 2 kilometres between Collins Gulch and Fraser Gulch, 3 to 4.5 kilometres southeast of Tulameen and 2.5 to 4.5 kilometres west-northwest of Coalmont.
Collins Gulch occurs along the northeastern margin of the Tulameen Basin, a structural basin comprised of a northwest- trending syncline that preserves a sequence of sedimentary rocks with lesser intercalated volcanics of the Eocene Allenby Formation (Princeton Group), up to 840 metres thick. The sequence rests unconformably on a basement of Upper Triassic Nicola Group metamorphosed volcanics and sediments. The syncline doubly plunges towards the centre of the basin. In the northwest, the fold is open with both limbs dipping approximately 45 degrees. In the southeast, the fold is asymmetric with the dips being approximately 45 degrees and 20 degrees on the northeast and southwest limbs, respectively. The basin is bounded by high-angle faults and is dissected by additional high-angle northwest to northeast-striking faults.
The deposit is hosted in a coal-bearing shale member approximately 130 to 200 metres thick, underlain by up to 120 metres of sandstone, siltstone and andesitic volcanics, and overlain by 580 to 700 metres of sandstone and pebble conglomerate, with interbeds of shale, ash and coal in the lower sections. The member consists of up to 30 metres of coal interbedded with mudstone, bentonite (ash) shale, and sandstone. The coal occurs in the lower 80 metres of the member in a zone of mostly brown to grey to black fissile shale and mudstone with lesser coal and white to buff bentonite, that ranges from 11 to 23 metres in thickness and contains 3.7 to 17 metres of clean coal (Coal Assessment Report 197, pages 3, 4).
Two seams of cleaner coal occur in Collins Gulch, 4.0 kilometres southwest of its confluence with the Tulameen River. The seams are at least 1.8 metres thick and are separated by a stratigraphic interval possibly 6 metres thick. Much of this intervening strata may also be coal (Geological Survey of Canada Paper 52-19, page 10). Seven metres of concealed strata underlying the lower seam may be partially comprised of coal.
At the Bear's Den prospect, 1000 metres east-southeast of Collins Gulch, three seams of coal occur in a stratigraphic section 120 metres thick. The two upper seams were explored by adits. The upper, middle and lower seams are 9.1, 8.8 and 4.0 metres thick respectively, and contain 8.61, 8.08 and 4.0 metres of clean coal respectively (Geological Survey of Canada Paper 52-19, Figure 1A).
At the Fraser Gulch prospect, 1800 metres southeast of Collins Gulch, four coal seams, 1.2 to 7.3 metres thick, were intersected in one drillhole over 13.7 metres (Coal Assessment Report 197, pages 3, 4).
The coal-bearing horizon generally strikes 110 to 130 degrees over most of its length and dips about 45 degrees southwest. Individual beds dip 35 to 80 degrees southwest. Coal-bearing sections are exposed discontinuously over a strike length of 1850 metres. The coal zone is estimated to contain inferred reserves of 5.6 million tonnes over a strike length of 4300 metres to a depth of 46 metres (Wright Engineers Ltd., 1970, page 2-4). Drill indicated reserves at Bear's Den and Fraser Gulch are 1.59 million tonnes over a strike length of 1500 metres to a depth of 60 metres, with a coal to waste ratio of 3 to 1 (Coal Assessment Report 198, page 1).
The coal is non-agglomerating to weakly agglomerating and is high-volatile bituminous B in rank. The material is commonly crushed and broken up due to shearing related to the folding of the strata. Four samples analysed as follows (in per cent):
Sample 1 Sample 2 Sample 3 Sample 4
Moisture 4.65 5.08 7.87 3.26
Volatile matter 32.67 31.58 30.59 43.33
Fixed carbon 54.83 57.06 51.10 49.70
Ash 7.85 6.28 10.44 3.71
Sulphur 0.31 - - -
Calorific value 12440 - - -
(B.T.U.'s per pound)
Coke yield - nil nil 53.41
Sample 1 is from drill core (?) from a hole drilled at Fraser Gulch (Coal Assessment Report 198, certificate of analysis). Samples 2 and 3 are from the same seam exposed at Collins Gulch (Minister of Mines Annual Report 1901, pages 1177, 1178). Sample 4 is also from Collins Gulch, which produced a tender but coherent coke (Geological Survey of Canada Summary Report 1909, page 116).
A sample of clay taken from an adit at Collins Gulch was found to be quite plastic. Preheating to 550 degrees Celsius did not destroy the plasticity of the material but permitted slow drying without cracking. The clay has an air shrinkage of 5.3 per cent and a fire shrinkage of 8 per cent at cone 5. Absorption at this cone is 6.8 per cent. The clay is not fused up to cone 13, but is not a fire clay (Geological Survey of Canada Memoir 24, page 116).
The deposit was explored in early 1901 by Nicola Coal Company. Columbia Coal and Coke excavated a number of adits at Collins Gulch, Bear's Den and Fraser Gulch between 1910 and 1913. The company abandoned the prospect because of the excessive shearing of the coal, and continued development of its holdings on Blakeburn Creek (092HSE 157). The exposure at Collins Gulch was re-examined in 1948, leading to the excavation of two adits by Collins Gulch Collieries Ltd. in 1950 and 1951. The company produced 257 tonnes of coal in 1951 (Minister of Mines Annual Report 1951, page 249). Geological mapping, trenching and drilling were conducted by Netherlands Acceptance Corporation and Cyprus Anvil Mining Corporation between 1974 and 1982.