New Denmark Colliery reserves occur within the Vryheid Formation of the Ecca Group within the Karoo Sequence. Sixty boreholes have been drilled by the mine to the base of the Karoo Supergroup in the MRA from which geological information could be derived. The thickness of the sediments underlying the No. 4 coal seam varies between 50 and 300 m. The coal-bearing Ecca Group ranges in thickness from 125 - 360 m and is comprised of an upper shale-like stage, the Volksrust Shale Formation, the mainly sandy coal measure stage, the Vryheid Formation, and a locally developed lower silt to shale stage, the Pietermaritzburg Shale Formation. The Vryheid Formation sediments developed in the NDC area are similar to those occurring elsewhere in the Highveld and Witbank Coalfields and are comprised mainly of sandstone, with lesser amounts of sandstone / siltstone and mudstone.

New Denmark is mined the No. 4 Seam. The No. 4 Seam is comparatively narrow at an average height of 1.8 m, being as low as 1.6 m in places.

Only underground mining methods are employed. The coal seam is accessed by means of three shaft systems (Central Shaft, North Shaft and Okhozini Shaft). The following underground mining methods are presently employed and are envisaged to continue until the end of the life of the mine.

Continuous miner mechanised mining is used to develop the bord and pillar primary, secondary and tertiary developments. The coal seam is mined to its full thickness. This method of development was selected on the grounds of productivity, requiring less equipment and less manpower than conventional mechanisation. The primary development is the main development on the mine. It offers primary access to the coal seam. The number of roadways is determined by the ventilation requirements. The centre set of roadways carry intake air and is flanked by two further sets of roadways, that carry return air. The secondary development is developed off the primary access to give access to mining reserve blocks. These developments also consist of central intake airways flanked by two return airways that are separated by a solid pillar. The number of roadways is also determined by the ventilation requirements.

The tertiary development is developed off the secondary developments to give access to each individual block. The number of roadways is also dependent on the ventilation requirements. Three road chain developments are developed off the tertiary developments to allow access to the tota ........

The coal processing plant is basically comprised of the Crusher Plant. The Crusher Plant is located between the North and Central Shaft areas and adjacent to the Coal Stockyard.

In order to meet the more stringent coal quality requirements of Eskom, NDC proposes to construct a De-Stoning Plant adjacent to the existing Crusher Plant.