Name and Location
Cullinan C-Cut expansion programme, Gauteng, South Africa.

Client
Petra Diamonds (74%), Thembinkosi Mining Investments (14%) and the Petra Diamonds Employee Share Trust (12%).

Project Description
The Cullinan mine contains a world-class resource base of 200.8-million carats, including 17-million carats in tailings. Petra plans to capitalise on this by undertaking an expansion programme to increase production to 2.2-million carats a year by the 2019 financial year.

This expansion plan, known as C-Cut Phase 1, will establish a new block cave on the western side of the orebody, in the upper portion of the major C-Cut resource, which is estimated to contain 133-million carats and will also involve a large tailings operation.

The development plan will enable the tonnage profile to gradually switch from diluted to undiluted ore. As a result run-of-mine (RoM) grade is expected to increase in future years to about 35 carats per hundred tonnes (cpht) by the 2015 financial year, 37 cpht by the 2016 financial year and to more than 50 cpht by the 2019 financial year, when the C-Cut Phase block cave is in full production.

Petra’s current mine plan has a life of 17 years, but the major residual resources at the mine indicate that the actual life-of-mine could be more than 50 years.

Value
Not stated.

Duration
The plan is to increase production from one-million carats in 2011 to 2.2-million carats by the 2019 financial year.

Latest Developments
The C-Cut expansion project was 50% complete in terms of the physical development work and capital expenditure in December 2014.

The new block cave, which is part of the C-Cut project, will deliver its first ore in the 2016 financial year (FY), which will be followed by a production build-up in FY 2017 and FY 2018 to its target of four-million tons a year by FY 2019.
Petra is using near-infrared (NIR) technology as part of its waste-sorting process to identify and remove waste from coarse-size fractions of +32 mm.

The NIR equipment has been fully commissioned and is currently operational at the mine.

The NIR technology is an important initiative at Cullinan, as the dilution of waste rock, compared with diamond-bearing ore – which the mine is currently encountering in the mature mining blocks – is compounded by increased waste rock from the mine’s development activities.

The waste tonnages have to be processed through the plant along with the mining tonnages, as the mine does not have separate waste-handling facilities. “The host rock at Cullinan consists of granite, which negatively affects the cyclone separation process in the plant,” says CEO Johan Dippenaar, adding that discarding waste will, therefore, help to free up plant feed capacity and reduce general wear and tear at the plant.

Dippenaar further highlights that waste reduction increases throughput, which adds to the mine’s capacity to treat fresh underground run-of-mine material: “Higher throughput improves our chances to recover the full spectrum of diamonds from the orebody, including the high-value special diamonds for which Cullinan is known.”

Key Contracts and Suppliers
Murray & Roberts Cementation (deepening of Shaft 1 and Shaft 3, as well as associated infrastructure and planned level development) and ABB (upgrade of the Koepe winder and ropes).

On Budget and on Time?
Not stated.

Contact Details for Project Information
Petra Diamonds, tel +27 11 702 6900, fax +27 11 706 3071 or email info@petradiamonds.com.
Murray & Roberts Cementation, tel +27 11 201 5000.
ABB (South Africa), tel +27 10 202 5000 or fax +27 11 579 8000.