Modern Mining October 2015

DIAMONDS

this approach include a reduced risk of ramp failure (once two splits join then a concentric ramp results), lower capex for the ini- tial mining fleet (due to lower waste) and less in-pit traffic con- gestion with multiple ore and waste faces available. The stay in business capital and operating costs for the proj- ect have also been reviewed in detail and, taking into account inflation, better cost definition and risk mitigation, they have increased in rand terms by R323 million and R1,9 billion respec- tively. Following the devaluation of the rand against the US dollar (R10:US$1 used in the 2013 DFS versus R13,27:US$1 used in the

mine plan), this translates to an increase in stay in business capital of US$20,6 million and a decrease in operating costs of US$56,8 million. These changes have been included to reduce the overall risk of delivering the mine plan. The 2013 DFS used a base case average diamond price of US$107/ct with an upside average large stone potential of US$156/ct both at a 1 mm BCO. In preparation for defin- ing parameters for running the mine plan, independent consultants were appointed to re-price the Liqhobong pilot plant produc- tion parcel and compile an updated August 2014 US$/ct diamond revenue estimate. The 2014 US$/ct revenue estimate was based on a combination of modelled size frequency distributions (SFD) per facies and modelled

reducing the overall diamond resource grade from 33 to 28 carats per hundred tonnes (cpht) and the total diamond resource carats from 29,7 to 23 million carats (Mct). As a result the undiluted mine plan grade has reduced from 32 cpht to 27 cpht, thereby resulting in a 17 % reduction in the overall carats recovered over the mine plan, which is partially offset by an increase in the diamond price as described below. When combined with the reduced waste stripping associated with the new split shell mine design, the favourable rand/US dollar exchange rate and the changes to the modelled cash flow, the overall rand revenue per tonne for the mine plan has improved. As indicated above, a split shell design has been adopted for the open pit. Advantages of

Open pit design. Overall basalt slope angles range from 50 to 55 deg. Kimber- lite angles range from 40 to 46 deg.

Main plant terraces: -6 m, 0 m and +8 m (September 2015).

30  MODERN MINING  October 2015