​Liddell Colliery is located in the Hunter Coalfield, within the north-eastern portion of the Sydney Basin. The north-eastern boundary of the basin is the New England Block and is marked by the Hunter–Mooki thrust.

The coal seams currently mined at the Liddell Colliery include the Lemington, Pikes Gully, Arties, Liddell and Barrett seams.

The coal seams targeted by current and future mining operations range from 0.7 metres to 9.5 metres in thickness and include semi-soft and thermal coal types.

Liddell's Measured plus Indicated Resources within the Colliery Holding boundary were 325.1 million tonnes (Mt) of coal (approximately 40 years at 8Mtpa) at 30 June 2006.