The Bromley Vale Collieries are situated on Bromley Creek, about 7 kilometres west-southwest of Princeton. The extensive underground workings of the two mines (Nos. 1 and 2) underlie district Lots 385 and 970.

This coal deposit is near the western margin of the Princeton Basin, a northerly trending half-graben superimposed on volcanics and sediments of the Upper Triassic Nicola Group. The basin is separated into a northern and southern area by the gentle, northwest-striking Rainbow Lake anticline. The southern area, in which this deposit occurs, is a structural depression with beds dipping 10 to 20 degrees south near Princeton, and gently east between Asp (China) Creek and the Tulameen River. South of Princeton are two major east-striking asymmetric anticlines with gentle to moderate southerly dips continuing to the south. On the western margin of the basin, the strata dips approximately 50 degrees east. In the southern part of the basin, two north to northwest plunging anticlines are present. The basin is bounded and cut in places by a number of approximately north to northeast-striking, westerly dipping faults. The main faults are the Asp Creek fault and the Boundary fault.

The deposit is hosted in a sequence of sandstone, shale, waterlain rhyolite tephra (tuff) and coal, up to 2000 metres thick, comprising the Eocene Allenby Formation (Princeton Group). The mines are developed in the upper two of four significant coal-bearing zones in a 530-metre section in the Allenby Formation. The No. 1 mine lies in the Gem-Bromley Vale zone, the lower of the two zones mined at Bromley Creek. This zone was also mined at the Gem mine (092HSE151), to the northeast. The No. 2 mine is developed in the overlying Golden Glow zone.

The deposit in the No. 1 mine strikes approximately 178 degrees and dips 20 to 37 degrees east, averaging about 25 to 27 degrees. Dips appear to shallow with depth. The seam has been traced in the mine along strike for 1440 metres and downdip for 430 metres. Minor faulting is evident in the underground workings. The deposit is 3.7 to 4.9 metres thick and contains at least 18 bands of bentonite, clay, shale and dirty coal up to 0.29 metre thick. Cleaner coal is contained in the lower 1.5 to 2.0 metres, from which all mine production originated.

The coal seam in the No. 2 mine is 2.0 metres thick and dips approximately 20 degrees east. It was mined over a strike length of 290 metres and a dip length of up to 100 metres.

The coal is non-coking in character and has a rank of sub-bituminous B. Two samples from the No. 1 mine analyzed as follows:

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Sample 1 Sample 2

(per cent) (per cent)

Moisture 12.8 13.9

Volatile matter 31.68 28.3

Fixed carbon 47.44 44.1

Ash 8.08 13.7

Sulphur - 0.63

Calorific value - 8560

(B.T.U.'s per pound)

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Sample 1 is a grab (?) sample (Minister of Mines Annual Report 1932, page 142), and Sample 2 is a sample of mine-run coal (Bulletin 14, page 19). Four additional samples from the No. 1 mine contained 14.8 to 17.6 per cent moisture, 27.0 to 31.9 per cent volatile matter, 37.4 to 49.4 per cent fixed carbon, 6.0 to 17.3 per cent ash, 0.44 to 0.64 per cent sulphur, and 7400 to 9424 British Thermal Units per pound (Bulletin 14, page 19).

The No. 1 mine was operated by Bromley Vale Collieries Ltd., (1932-1933), Cascade Coal Company Ltd. (1934), Diamond Black Collieries Ltd. (1935-1936) and Granby Mining, Smelting and Power Company Ltd. (1937-1943). Production ceased in 1943, after excessive squeezing was encountered in the deeper workings, partly as a result of the expansion of bentonite seams associated with the coal. The No. 2 mine, situated above the southeastern workings of the No. 1 mine, was operated briefly by Granby in 1940 and 1941. Total production between 1932 and 1943 amounted to 462,083 tonnes. Most of this coal was used to fuel Granby's steam-electric power station near Princeton.