The Kimberley Underground mines are located within the historic city of Kimberley, the provincial capital of the Northern Cape Province in South Africa.
Kimberley Underground comprises Bultfontein, Dutoitspan and Wesselton, three historic diamond mines which were at the heart of the diamond rush in the Kimberley region of South Africa in the late 1800’s. Mining was commenced at Bultfontein and Dutoitspan in 1869 and at Wesselton in 1890.

The kimberlite pipes in the Kimberley area have intruded into the horizontally bedded, black and grey carbonaceous shales of the Karoo Supergroup, with minor interbedded sandstone and siltstone layers. This formation conformably overlies an erratically developed Dwyka tillite, which seldom exceeds three metres in thickness. This sequence has been intruded by a dolerite sill up to 30 metres thick. Locally this sill has acted as a barrier to kimberlite intrusion with the resultant formation of kimberlite sills at or near the base of the dolerite sill. The Karoo rocks unconformably overlie the Ventersdorp Supergroup strata of variable thickness. The Ventersdorp Lavas in turn unconformably overlie the uneven Basement Granite.

Total resources of the mines are estimated at 6.4 million carats.

In September 2007 Petra reached agreement to acquire Kimberley Underground from De Beers and the acquisition is expected to complete in the near future. As Kimberley Underground ceased production in August 2005, Petra has been operating the mines under care and maintenance, with ore being stockpiled for processing once the acquisition is complete. Construction of a new treatment plant by Petra at Joint Shaft has been completed.