The various underground workings of the Princeton Colliery lie mostly east of the Similkameen River, adjacent to the town of Princeton (Nos. 1 and 2 mines). Some of the workings are in the town itself near the west bank of the Similkameen River (No. 3 (New Shaft) mine).

This coal deposit is situated near the eastern 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-trending 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-trending asymmetric anticlines with gentle to moderate southerly dips continuing to the south. On the western margin of the basin, the strata dip 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 and Boundary faults.

The Princeton Colliery 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 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 from approximately 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 the Princeton-Tulameen mine (092HSE209), Tulameen Collieries (092HSE210), the Pleasant Valley Nos. 2 and 4 mines (092HSE211), the Black mine (092HSE212) and the Blue Flame Colliery (092HSE216).

The coal seam at the Princeton Colliery strikes approximately 040 degrees and dips 8 to 16 degrees south. The seam has been traced downdip in the No. 1 mine, the deepest of the three mines, for 640 metres. The three mines followed the seam over a total strike length of 1100 metres. The deposit is displaced along a northeast striking fault that separates the Nos. 1 and 2 mines.

The mined seam is 1.8 to 3.2 metres thick and contains minor clay, as bands usually between 3 and 19 millimetres thick. It forms the uppermost section of a sequence of dirty coal, shale, clay and clean coal, 5.5 to 7.3 metres thick.

The coal is non-coking in character and ranges in rank from sub-bituminous B to sub-bituminous A. The coal is jet black and resinous in appearance, and of low specific gravity. It frequently breaks with a conchoidal fracture. Two samples from the No. 1 mine analyzed as follows:

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Sample 1 Sample 2

(per cent) (per cent)

Moisture 16.17 11.97

Volatile matter 37.58 30.49

Fixed carbon 41.67 49.21

Ash 4.58 8.33

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Sample 1 is a selected grab sample (Geological Survey of Canada Memoir 69, page 261). Sample 2 is a channel sample taken across 2.4 metres of coal with occasional thin shale bands (Minister of Mines Annual Report 1901, page 1176). Four additional samples from the Nos. 1, 2 and 3 mines contained 15.29 to 18.0 per cent moisture, 28.5 to 33.0 per cent volatile matter, 42.8 to 49.7 per cent fixed carbon, 5.4 to 9.2 per cent ash, 0.4 to 0.7 per cent sulphur, and 9850 to

10540 British Thermal Units per pound (Bulletin 41, page 16; Geological Survey of Canada Memoir 243, pages 116, 117).

The deposit was initially explored by Vermillion Mining and Development Company Ltd. between 1901 and 1908. The Princeton Coal and Land Company Ltd. commenced production in December 1909 with the development of the No. 1 mine. Declining reserves and spontaneous combustion of old workings in the No. 1 mine prompted the company to develop the No. 2 mine, southeast of and adjacent to the No. 1 mine, which commenced production in 1923. After encountering coal of poor quality in the No. 2 mine, Princeton-B.C. Colliery Company Ltd. (formerly Princeton Coal and Land Company) abandoned both mines in 1924 and developed the No. 3 (New Shaft) mine to the northwest, across the Similkameen River. This mine operated briefly during 1925 and early 1926, having to shut down due to excessive inflow of groundwater. A total of 359,150 tonnes of coal were produced from the underground workings. An additional 1585 tonnes of coal were stripped from outcrops at the No. 1 mine by J.P. Wukelick between 1949 and 1951.

A few potentially economic seams of bentonite occur in the Princeton-Black-Blue Flame coal zone, usually overlying or underlying coal seams. One bentonite bed occurs in a shale member known informally as the Vermillion Bluffs shale, underneath the coal seam in the No. 2 mine (Open File 1987-19). The bentonite seam is 0.45 metre thick, and is comprised of creamy white clay.

A second bed of greyish, white-weathering clay (bentonite?) occurs in the No. 1 mine, 4.3 metres above the mined coal seam. The bed is 0.6 metre thick and comprised of fine-grained, non-refractory clay that is quite sticky and plastic. A sample contained 75.20 per cent total silica, 3.66 per cent hydrous silica, 11.39 per cent Al2O3, 1.83 per cent Fe2O3 and 0.21 per cent carbonaceous matter (Geological Survey of Canada Memoir 65, page 27). The excessive shrinking and cracking experienced during air drying was almost completely eliminated by preheating the clay to 300 degrees Celsius. Air shrinkage was thus reduced to 5 per cent. The firing characteristics of the preheated clay are as follows (Geological Survey of Canada Memoir 65, page 29):

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Cone Fire shrinkage Absorption

(per cent) (per cent)

010 0.6 25.15

05 2.0 25.50

1 4.0 19.36

5 5.0 18.80

9 6.0 16.80

12 6.0 15.00

15 Fused -

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The clay burns to a porous, buff-coloured body that is rather light in weight.