Annual Report and Accounts 2011

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At a Glance About About

Revenue contribution:




Diamonds sold

31,555 carats

Average price per carat


There was no treatment of main pit material at Williamson in FY 2011, as the project to rebuild the 3 Mtpa plant was underway. Contract mining of alluvial diamonds recovered 29,510 carats, sold for an average value of US$302. Alluvial production is expected to be lower in FY 2012 due to the depletion of available alluvial gravels.

The ROM stockpile at Williamson, which has been established by Petra due to the pit-shaping operations, increased to approximately 900,000 tonnes as at 30 June 2011, estimated to contain in excess of 45,000 carats.

image of men at side of road

Development plan update

The rebuild of the original plant at Williamson has progressed well. As previously announced, Petra revisited its plans with regards to this plant, deciding to carry out an enhanced rebuild rather than a lower key refurbishment. The rebuilt plant is expected to be in production in Q3 FY 2012. It is anticipated that this 3 Mtpa plant will treat approximately 0.5 to 0.9 Mt in FY 2012, at an expected grade of 6 cpht.

Capex at Williamson of US$36.6 million (including US$0.8 million borrowing costs capitalised) was spent as follows:

  • US$18.8 million on the rebuild of the 3 Mtpa plant; and
  • US$17 million on other production related activities, including pit shaping/shale removal, haul road construction and slime handling facilities.

Over recent months, there have been power supply issues in Tanzania which have impacted upon likely power supply to the mine. The Government of Tanzania is addressing these power supply issues and the Company continues to monitor the situation carefully. Due to these power disruptions that have been experienced on mine, orders were placed for generators that will provide sufficient power to run the 3 Mtpa plant. The anticipated production for FY 2012 is therefore lower than the guidance given in Petra's Trading Update of 19 July 2011 as the planned start-up of the rebuilt plant has been deferred until the standby electricity is available.

These electricity supply issues have also meant that the Company is revisiting the timing of the longer-term expansion project, where the Company has previously announced that it is planning to establish a 10 Mtpa operation. Further information will follow in due course when the Company has completed its analysis, including the revised timing of the roll-out of the new plant.

FY 2011 – gross numbers

  Unit FY 20111 FY 20101 Variance
Revenue US$m 9.5 14.4 -34%
Diamonds sold carats 31,555 91,901 -66%
Average price per carat US$ 302 157 +92%
ROM production      
Tonnes treated tonnes n/a 1,334,656 n/a
Grade cpht n/a 6.3 n/a
Diamonds recovered carats n/a 84,241 n/a
Alluvial production      
Tonnes treated tonnes 530,689 423,665 +25%
Grade cpht 5.6 4.0 +40%
Diamonds recovered carats 29,510 16,830 +75%
Total production      
Tonnes treated tonnes 530,689 1,758,321 -70%
Diamonds recovered carats 29,510 101,071 -71%
Cash cost per tonne1 US$m n/a n/a n/a
Total capex US$m 36.6 11.6 n/a

1. During FY 2010 the mine was in a bulk sampling phase and in FY 2011 the mine results represent alluvial production only; neither period reflects
    conditions associated with normal production.