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DIAMONDS
30
MODERN MINING
November 2016
T
he C-Cut project forms part of
Petra’s overall strategy to shift pro-
duction at its underground mines
in South Africa from mature,
diluted caves to new undiluted
production blocks. As Andre Cloete, Petra’s
Project Manager for the C-Cut points out, the
intention is not to increase ROM production
levels but to achieve grade (higher diamond
content per tonne mined). “The problem with
mature caves is that they become increasingly
diluted with waste rock,” he explains. “This
dilution is now quite severe at mines such as
Cullinan, Finsch and Koffiefontein and has
negatively impacted on ROM grades. In the
case of Cullinan, the C-Cut will see the ROM
grade – presently running at around 33 cpht –
increase to approximately 50 cpht by 2019.”
He adds that the move to new production
blocks will have additional benefits, over and
above the undiluted ore and resultant increase
in grades. “The reduced amount of waste rock
to be handled will lead to reduced wear and
tear on machinery, as the waste rock is typically
much harder than the kimberlite ore, while the
overall product mix will also improve.”
The C-Cut is a project first proposed by De
Beers, the previous owner of Cullinan, back
in the 1990s. De Beers took the project to an
advanced study stage and (in 2002) estimated its
Cullinan’s C-Cut
starts its
Crusher 1 South, which was
commissioned in July 2016.
Development of one of the deepest mechanised kimberlite block caves in the world – the C-Cut at
Petra Diamonds’ Cullinan Diamond Mine (CDM) near Pretoria – is now at an advanced stage, with
the project over 80 % complete and already delivering its first ore.
Modern Mining
recently went un-
derground at Cullinan in the company of Petra management and personnel fromMurray & Roberts
Cementation, the biggest contractor on the project, to view the progress being made on the new cave,
which by 2019 will be producing ore at a steady-state rate of around 3,7 Mt/a.