Finsch

Finsch is one of the world’s important diamond mines and South Africa’s second largest diamond operation by production. The mine benefits from state-of-the-art mining infrastructure, including a modern processing plant which was recently upgraded at a total cost of approximately US$100 million.

Finsch produced an average of approximately 2 million carats per annum over the five years to 2010, from a combination of underground mining and tailings retreatment, and has produced 126 million carats in its 40 plus year life to date. Petra is currently implementing a development plan to lift production from 1.5 million carats per annum to around 2 million carats per annum by FY 2018 (involving both underground and tailings production).

Finsch has produced a number of large, special diamonds in its history and mine records reflect the recovery of an average of 27 stones of more than 50 carats per annum over the last four years. Recovery of such large, high-value stones can substantially increase the total value of production in any one year. In addition, the mine has produced a range of coloured diamonds, including pinks and yellows.

The Finsch kimberlite was discovered in 1960 and the mine was officially opened in 1967. Ore extraction was initially from the open pit. Sinking of the main shaft to access the mine from underground started in 1978. Two vertical shaft complexes, tunnels and ground handling infrastructure were prepared for the continuing exploitation of the pipe with the use of highly mechanised mining methods. In 2008 the treatment plant was upgraded at a cost of approximately US$100 million.

On 14 September 2011, Petra purchased Finsch as a fully-staffed, operating mine from De Beers.

• Resource bottom cut-off: 1.47mm
• Reserve bottom cut-off 1.47mm
• Reserve tonnes and grade are based on block cave depletion modelling, and include external waste

Petra’s current mine plan forecasts initial diamond production of approximately 1.5 Mctpa (comprising approximately 900,000 carats from underground and 600,000 carats from tailings) increasing with the commencement of the Block 5 cave to a steady state production of nearly 2 Mctpa.

Subsequent to the depletion of Block 4, underground production will be derived principally from Block 5, a new block cave beneath the current operations, which has Probable Reserves of 22.1 Mcts at a grade of 47.6 cpht. Petra intends to maintain production levels from underground during the transition from the Block 4 block cave to the Block 5 block cave by developing smaller sub-level caves within the Precursor orebody (adjacent to the main orebody) at Block 4 level and within Block 5 itself. By so doing, Petra expects to maintain underground production levels at approximately 3.2 Mtpa, ramping up to around 3.5 Mtpa by FY 2018 once the Block 5 cave is fully operational.

Underground production is supplemented by tailings retreatment. Finsch is currently treating the pre-1979 TMR (tailings from mining operations pre-1979) which has a recovered grade of approximately 18.1 cpht. The pre-1979 TMR is expected to be treated at a rate of approximately 3.5 Mtpa until depleted in FY 2015. Thereafter, the post-1979 TD (tailings from mining operations post-1979), which carry a lower grade of approximately 10 cpht, remain available for treatment. It is expected that tailings production will cease in FY 2020.

Given the major resource base of 43.7 Mcts at Finsch (including 25.8 Mcts in the reserves category and 2.5 Mcts in tailings), Petra foresees a long life for the operation and has a current mine plan of 18 years, though the orebody remains open-ended at depth.