Cullinan Diamond Mine, a member of the Petra Diamonds group, has awarded Murray & Roberts Cementation a contract that includes the deepening of Shaft 1 and Shaft 3 at the Cullinan diamond mine, together with the associated infrastructure and planned level development to the Cullinan ore body.

The contract is part of a major expansion plan at Cullinan, which will take production from just under 1 million carats in 2011 to 2.4 million carats by 2019, incorporating 2 million carats from underground production and 0.4 million carats from a major tailings programme. The mine is currently producing about 9.2 kilotons per day (ktpd) from three mining blocks on two horizons at the mine.

Allan Widlake, business development director at Murray & Roberts Cementation, says Cullinan’s life of mine profile requires the opening up of a new block cave in the C-Cut Phase 1 area of the Cullinan kimberlite pipe, 200 metres below the current operations. This new block will access the first portion of the C-Cut resource, beneath the existing production levels at the mine.

“The C-Cut Phase 1 is planned for a steady state production rate of circa 4 Mtpa, with the first column tonnages reporting in calendar year 2016,” he explains. “Access to the C-Cut Phase 1 block is through a decline system from the 763 metre level on the southern and northern sides of the kimberlite pipe, deepening of the existing No 1 rock hoisting shaft to handle waste and ore from the future mining areas and deepening of the existing No 3 men and material shaft to deliver personnel and material to the underground workings.”

The Shaft 1 portion of the contract scope entails deepening the existing shaft by approximately 350 metres to a depth of 920 metres. The deepened shaft will be equipped to hoist the ore and waste from the new C-Cut Phase 1 block. The equipping scope includes a new shaft bottom/loading arrangement as well as water handling facilities.

“The shaft needs to be equipped to handle mid shaft loading, as it is expected that ore from the current operations will report to the existing loading arrangement until the connection between the current operations and the C-Cut Phase 1 ore/waste handling systems has been made,” Widlake says.

The Shaft 3 portion of the contract scope involves deepening the existing shaft by approximately 60 metres to a depth of 904 metres. This shaft will be equipped to handle personnel and material to and from the new C-Cut Phase 1 block.

All engineering requirements, except upgrades to the Koepe winder and ropes which will be handled by power and automation technology group ABB, are included in this contract.

The Cullinan mine is situated near Pretoria, in the Gauteng province. Cullinan is one of the world’s most celebrated diamond mines and has produced more than 700 stones sized greater than 100 carats and more than a quarter of the entire world’s diamonds of greater than 400 carats. It is also the world’s only significant source of truly rare and highly valuable blue diamonds. Since taking over the mine in July 2008, Petra has recovered several world-class diamonds, including a 39 carat blue diamond, a 26 carat blue diamond and a 507 carat white diamond that was sold for US$35.3 million, the highest price on record for a rough diamond.