The various underground workings of the Tulameen Collieries occupy an area bounded to the east and south by the Tulameen River, adjacent to the town of Princeton. This area covers all of district Lot 248 and the extreme east end of the adjoining district Lot 1133.

The deposit is in the centre 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 Tulameen Collieries are 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 mine is developed in the Princeton-Black-Blue Flame coal zone, the stratigraphically lowest and thickest of four significant coal- bearing zones in a 530-metre section in the Allenby Formation. Its thickness varies from 1.6 to 19.2 metres, with approximately 9.1 metres of coal. The coal occurs in bands 7 centimetres to 5.5 metres thick, with interbeds of shaly coal, bentonite, sandstone, and shale separating the individual seams. The partings and beds associated with the coal change thickness and stratigraphic position laterally, making correlation difficult. Coal quality also varies laterally. The Princeton-Black-Blue Flame coal zone was also mined at Princeton Collieries (092HSE089), Princeton-Tulameen mine (092HSE209), the Pleasant Valley Nos. 2 and 4 mines (092HSE211), the Black mine (092HSE212) and the Blue Flame Colliery (092HSE216).

The coal seam at the Tulameen Collieries strikes 005 to 020 degrees and dips 8 to 15 degrees east. The dip steepens with depth. Three underground mines, the Nos. 1, 2 and 3 mines, have traced the seam downdip for 800 metres and along strike for 840 metres.

The mineable coal is 2.1 to 3.4 metres thick and contains five thin clay partings. It is overlain by a fairly competent shale and underlain by a sequence of dirty coal, shale and clay, 4.0 to 4.9 metres thick, similar to other mines in the eastern part of the Princeton-Black-Blue Flame coal zone (092HSE089, 209).

The coal is non-coking in character and has a rank of sub-bituminous A to high-volatile bituminous C. Three samples from the No. 1 mine analyzed as follows (Bulletin 14, page 16, 20):

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Sample 1 Sample 2 Sample 3

(per cent) (per cent) (per cent)

Moisture 15.50 15.90 19.7

Volatile matter 30.60 29.90 -

Fixed carbon 49.20 49.70 -

Ash 4.70 4.50 9.5

Sulphur 0.30 0.33 -

Calorific value 10540 10540 9360

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

Ash Fusion Temp. - - 1159 C

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Sample 1 is from the lower bench, while sample 2 is from the top bench. Sample 3 is a bulk sample. Three additional samples from the No. 2 mine analysed 56.37 to 56.50 per cent volatile matter, 21.76 to 39.73 per cent fixed carbon, 3.77 to 4.90 per cent ash, 0.34 to 0.65 per cent sulphur, and 12,100 to 12,630 British Thermal Units per pound (Geological Survey of Canada Memoir 243, pages 116, 117, samples 3, 4 and 5).

The deposit was mined in the northeast in two adjacent mines, the Nos. 1 and 2 mines, by C. Hunter (1924), Tulameen Valley Coal Company (1925-1928), Tulameen Coal Mines Ltd. (1929-1934) and Tulameen Collieries Ltd. (1935, 1936). The mines were abandoned in 1936 because of excessive inflow of groundwater in the No. 2 mine. The No. 3 mine was opened to the southwest by Tulameen Collieries in 1941. This mine was eventually connected with the No. 2 mine, to recover coal left in pillars. Small amounts of coal were also recovered from pillars near surface in the Nos. 1 and 2 mines during this time. Production ceased in 1946. A total of 498,442 tonnes of coal was produced between 1924 and 1946.