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DIAMONDS
30
MODERN MINING
October 2015
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
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
Main plant terraces: -6 m,
0 m and +8 m (September
2015).
Open pit design. Overall
basalt slope angles range
from 50 to 55 deg. Kimber-
lite angles range from 40 to
46 deg.