Open pit mining at Williamson in Tanzania

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Gross Reserves & Resources

Petra manages one of the world’s largest diamond resources. This major resource implies that the potential mine lives of Petra's core assets could be considerably longer than the current mine plans in place at each operation, or could support significantly higher production rates.

Gross Reserves and Resources
As at 30 June 2013, the Group’s gross Diamond Resources (inclusive of Reserves) had increased by 2.5% to 309.6 Mcts, from 302.1 Mcts as at 30 June 2012. This is mainly due to an increase in gross Resources at Finsch as a result of decreasing the bottom cut off used in the Resource estimation from 1.5mm to 1mm. This is in line with the decrease to the bottom cut off at the Finsch production plant, effected by Petra during FY 2013, thereby serving to increase the grade and recoverable carats over the life of mine.

The Group’s gross Diamond Reserves increased 14.3% to 54.4 Mcts (30 June 2012: 47.6 Mcts), mainly due to an increase in gross Reserves at Cullinan. This has resulted from the increased number of new tunnels that have been brought into production and the detailed mine plans being run through the PCBC block cave scheduling and simulation software, thereby allowing for a more representative Reserves figure to be calculated.

The following table summarises the Reserves and Resources status of the combined Petra Group operations as at 30 June 2013.

Category Gross
Contained Diamonds
Proved 1.8 39.1 0.71
Probable 127.3 42.1 53.66
Sub-total 129.1 42.1 54.36
Measured 14.7 8.4 1.24
Indicated 452.4 49.5 224.09
Inferred 1251.3 6.7 84.25
Sub-total 1718.5 18.0 309.58

General notes on reporting criteria

  1. Resources are reported inclusive of reserves.
  2. Tonnes are reported as millions; contained diamonds are reported as million carats.
  3. Tonnes are metric tonnes, and are rounded to the nearest 1000 tonnes; carats are rounded to the nearest 1000 carats; rounding off of numbers may result in minor computational discrepancies.
  4. Resource tonnages and grades are reported exclusive of internal waste, unless where otherwise stated.
  5. Reserve tonnages and grades are reported inclusive of external waste, mining and geological losses and plant modifying factors; reserve carats will generally be less than resource carats on conversion and this has been taken into account in the applicable statements.
  6. Reserves and Resources have been reported in accordance with the South African code for the reporting of mineral reserves and mineral resources (SAMREC 2007).
  7. The Petra 2013 annual Resource Statement as shown above is based on information compiled internally within the Group under the guidance and supervision of Jim Davidson, Pr. Sci. Nat. (reg. No.400031/06). Jim Davidson has over 30 years' relevant experience in the diamond industry and is a full-time employee of Petra.
  8. All Reserves and Resources have been independently reviewed and verified by John Kilham, Pr. Sci. Nat. (reg. No. 400018/07), a competent person with 33 years' relevant experience in the diamond mining industry, who was appointed as an independent consultant by the Company for this purpose.

To read the Company’s full 2013 Resource Statement, click here.

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