The main seam in the J pit area is the lowermost or No. 10 seam of the Jurassic-Cretaceous Mist Mountain Formation (Kootenay Group). It averages approximately 15 metres in thickness and is interbedded with sandstone, siltstone and shale. Ash in the raw coal varies from 15 to 29 per cent with kilojoules per kilogram values of greater that 27,640. In the coal cleaned at 1.50 specific gravity, volatile matter varies from 21 to 29 per cent, ash content from 9.5 to 10 per cent, sulphur less than 0.5 per cent, and kilojoules per kilogram values are approximately 32,560. Proven reserves in the J pit area are 129,800,000 tonnes in place (1981 B.C. Coal Ltd., Reserve and Resource data).

The J pit area is located on the east (west dipping) limb of the Sparwood syncline (approximately north trending, south plunging). The No. 10 seam is offset by a number of north trending, west dipping, closely-spaced thrust faults.