The surface area of BK11 is presently modelled as 9.6Ha and overburden, consisting of Kalahari sands and calcretes, is relatively shallow at, on average less than, 4m. The overburden is underlain by intensely calcretised and silcretised low grade kimberlitic material up to a depth of approximately 20m.

A comprehensive exploratory drilling programme was undertaken to fully delineate the position, extent and morphology of the BK11 kimberlite pipe below the surface to a depth of approximately 150m, as well as to establish the mineral resource potential.

The BK11 kimberlite has been shown to be a classic “champagne glass” shaped pipe with a large crater bowl filled with layered volcaniclastic deposits (K2-K3) and talus slope deposits, commonly known as country rock breccia, closer to the crater walls. A rather less-well delineated “neck” of more massive volcaniclastic kimberlite (K4) and basalt breccia underlies the crater. The kimberlite is covered with a thin veneer of up to, on average, 4m of Kalahari sands and then gradational calcrete/silcrete units which are believed to be dominantly weathered K1 material. Several shaley kimberlite units are present in the upper pipe, dipping gently outwards from the K1 “knoll” in the centre of the pipe.

The western and central side of the kimberlite pipe at BK11 is characterised by a cleaner and subsequently higher grade kimberlite, containing a higher proportion of clear white crystals with very little bo ........

As the mining operations at BK11 were only active for a limited period of time, the kimberlite pipe was mined to a depth of approximately 60m. Due to its higher grade, mining operations focused initially on the Western Zone of the kimberlite pipe.

The mining operations at BK11, prior to the mine being placed on care and maintenance (in February 2012), consisted of ore being loaded from the open pit and/or existing stock piles by hydraulic excavators onto five 25t ADTs which then transported material to the BK11 Treatment Plant for processing and recovery of diamonds. An additional fleet of 6 ADTs was used for waste stripping and initial overburden removal. However as waste volumes increased a contractor was appointed to carry out the removal of waste rock. Drilling and blasting operations were also outsourced.

- subscription is required.