Name of the Project
Cullinan C-Cut Phase 1 expansion programme.

Location
Gauteng, South Africa.

Client
Petra Diamonds (74%), Kago Diamonds (14%) and the Itumeleng Petra Diamonds Employee Share Trust (12%).

Project Description
The Cullinan mine contains a world-class resource base of 195.4-million carats, including 17-million carats in tailings as of June 30, 2015. Petra plans to capitalise on this by undertaking an expansion programme to increase production to an estimated 2.2-million carats a year by the 2019 financial year, comprising 2.2-million carats run-of-mine (RoM) and 180 000 ct of tailings.

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. It will also involve a large tailings retreatment operation.

The development plan will allow for the tonnage profile to gradually switch from the old mining areas, heavily diluted with waste rock, to the new mining areas, thereby providing access to undiluted ore. As a result, the RoM grade is expected to increase  to 38 to 40 carats per hundred tonnes (cpht) in the 2017 financial year to about 49 to 51 cpht by the 2019 financial year, when the C-Cut Phase 1 block cave is in full production.

Petra’s current mine plan envisions a life-of-mine (LoM) to 2030, but the major residual resources at the mine indicate that the actual LoM could be more than 50 years.

Phase 2 of the C-Cut development, which is still at the conceptual phase and not included in the life-of-mine to 2030, aims to further expand Cullinan’s RoM production to four-million tons a year, with a yield of two-million carats a year between 2019 and 2030. The conceptual framework indicates that Phase 2 will expand the C-Cut by another 7.8 ha.

Jobs to be Created
A crew of 45 Murray & Roberts Cementation personnel is working on the project site; however, during the peak development phase of the programme, between May 2014 and May 2015, 386 employees were on site.

Net Present Value/Internal Rate of Return
Not stated.

Value
R4-billion.

Duration
The plan is to increase production from 729 496 ct to 2.2-million carats by the 2019 financial year.

Latest Developments
The new winder system at Cullinan has been commissioned and the remainder of the shaft will be commissioned by mid-December, after which the mine will no longer have to undertake midshaft loading. This will improve efficiencies and reduce the number of times that ore is rehandled from fourteen times to three.

Petra is undertaking the current expansion project to increase the mine’s production from 729 496 ct to 2.2-million carats by the 2019 financial year. Petra CEO Johan Dippenaar says Cullinan’s old mining areas have become “contaminated” with waste rock, which has resulted in the dilution of the ore grade and, therefore, lowered the mine’s earnings for each ton of ore treated. However, he points out that, through the implementation of the C-Cut project, pure kimberlite ore will in future be delivered to the mine for processing, thereby significantly enhancing the quality of diamonds produced.

The C-Cut expansion project 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. It will also involve a large tailings retreatment operation.

The new block cave at Cullinan is expected to deliver more than one-million tons of undiluted ore in 2017, while the mine’s plant is scheduled to be commissioned by May that year and start production a month later. Cullinan’s new R1.6-billion processing plant will ensure improved diamond liberation once in operation.

Mining services company Murray & Roberts Cementation is responsible for delivering the R1-billion shaft sinking contract, which was awarded in August 2012 and is the largest portion of the C-Cut Phase 1 expansion programme.

The Cullinan’s shaft headframe has had to be upgraded to meet the present codes of practice applicable to shaft headframes.

Murray & Roberts has reported that deepening of the shafts has been completed. Shaft 1, which is used for rock hoisting, was deepened from 580 m to 934 m, while compartments 3 and 4 of the shaft were commissioned on September 23. Compartments 1 and 2 will be commissioned by the end of this year. Shaft 3, which is a personnel and materials shaft, was deepened from 805 m to 885 m and handed over to Petra for operational use in May.

The final commissioning of the Shaft 1 compartments 1 and 2 is expected to be completed by the end of December this year.

Key Contracts and Suppliers
MDM Engineering (the South African division of Amec Foster Wheeler) Cullinan plant contract and Murray & Roberts Cullinan shaft contract.

On Budget and on Time?
The project is on time and within budget.

Contact Details for Project Information
Petra Diamonds, email info@petradiamonds.com.