A minimum of six coal seams occur in the Lower-Upper Cretaceous Gates Formation (approximately 200 metres thick) of the Fort St. John Group, interbedded with sandstone, siltstone, shale and minor pebble conglomerate, deposited in a deltaic setting. The sediments form a prominent broad syncline plunging gently northwest. In the Mount Chamberlain area the fold is asymmetrical (the west flank dips up to 70 degrees, the east flank dips at less than 20 degrees). To the south, the dips on both limbs are gentler where the West and South Fork areas lie along the axial portion of the fold, with dips less than 20 degrees. A northwest trending thrust fault at West Fork dips southwest and shows appreciably large displacement. A thrust fault at South Fork appears to show little displacement.

The coal seams in ascending stratigraphic order are A, B, C, D, E and F seams. Quality and thickness vary between and also within seams. Generally, seam characteristics improve from younger to older and most of the seams also improve southwards. In the West and South Fork areas, the seams are thicker and more easily correlated than to the north, where they are frequently split and contain numerous rock partings.

Seam A is a thin coaly horizon in the northeast becoming thicker and cleaner to the south. The thickness averages 1.8 metres in the West Fork area (shaly parting up to 0.6 metre) and exceeds 4.5 metres in the South Fork area where the parting is also thicker (approximately 1.8 metres). Ash percentage is 7.2 and 13.2 (lower and upper) and 18.8 in the South and West Fork areas respectively and sulphur percentage is 0.35 to 0.45 (lower and upper) and 0.38 respectively.

Seam B is widespread and is most important because of its thickness. It is generally free of rock partings and appears hard and bright. In the north of the property, although thick, the seam is very shaly but thickens and improves in quality southwards. The B seam averages 3.4 metres and 4.8 metres in the West and South Fork areas respectively. The B seam contains 7.2 and 18.0 per cent ash (lower and upper) and 7.2 and 19.8 per cent ash (lower and upper) in the South and West Fork areas respectively, with sulphur values 0.23 per cent (lower and upper) and 0.25 per cent (lower and upper) respectively.

Seam C is 1.9 metres thick in 3 splits in the West Fork area and 1.8 metres at South Fork, including some dirt bands. Generally dull with some bright bands, ash percentage is 22.4 and 20.6 and sulphur 0.44 and 0.35 per cent in the South and West Fork areas respectively.

The D seam is variable in thickness and quality at West Fork, with the thicker sections having very high ash contents. Average ash and sulphur are 34.5 per cent and 0.26 per cent respectively at West Fork. The seam is more uniform and averages 1.5 metres thick at South Fork. Here it is dull and includes rock partings, with ash and sulphur percentages averaging 35.9 and 0.33 respectively.

The E seam is a distinct seam only at West Fork (less than 1 metre) and South Fork (greater than 1 metre). In the north it consists of several coaly horizons. The seam is thickest at South Fork (greater than 1 metre) where it is hard and bright with minor shale partings. Ash and sulphur percentages are 14.1 and 0.51 respectively at South Fork.

The F seam is represented by one or more coaly horizons in the southern part of the Bullmoose property, it does not occur at South and West Fork.

Volatile matter contents vary from 20.6 per cent (D seam) to 26.9 per cent (E seam) at South Fork and 20.4 (E seam) to 26.6 per cent (lower B seam) at West Fork. Free swelling index ranges from 2.5 to 5 with lower values more common at West Fork. Fixed carbon ranges from 43.6 per cent (D seam, South Fork) to 68.2 per cent (lower A seam, South Fork).

Three mining methods, depending on coal seam dip angles were used at the South Fork pit, which has a mineable reserve of 13.5 million tonnes before mining began. The mineral resource in the nearby West Fork zone was an estimated 14.3 million tonnes (T. Schroeter, personal communication, 1997).

The Bullmoose open pit mine operated continuously since production began in 1983 until closure in 2003, and shipped over 32 million tonnes of metallurgical coal to overseas steel producers. The open pit lies entirely south of West Bullmoose Creek. Reserves at December 31, 2001 were 2.8 million tonnes proven. Resources were 12 million tonnes measured, 10.3 million tonnes indicated and 2.6 million tonnes inferred (Teck Cominco Limited, Annual Report 2001).

The part of the Bullmoose property that lies north of West Bullmoose Creek (sometimes called Bullmoose Teck) was at times part of the Sukunka property. At the time of this update (2015) it is part of Glencore's Sukunka project.