Production at Mwadui diamond mine up

Posted on : Thursday , 29th October 2015

WILLIAMSON Diamond Mine, the subsidiary of Petra Diamonds, production rose by 7 per cent in the year 2015 to 202,265 carats compared to 188,465 carats in 2014, mainly due to the increase in Run of Mine (ROM) tonnes treated.
According to the Petra Diamonds Annual Reports and Accounts, revenue increased 15 per cent to 62.1 million US dollars in the year under review compared to 53.9 million US dollars posted in 2014 due to the higher proportion of ROM versus alluvial diamonds for the Year.

The high average value per carat of this mine remained relatively in line with the prior year at 298 US dollars compared to 303 in 2014. Similarly, the on-mine cash cost of 12/t US dollars compared to 11/t US dollars was in line with guidance.

Petra's expansion plan at Williamson will see tonnage throughput ramp up to circa 5 Mtpa from FY 2018, which, at a grade of circa 7.0 cpht, is expected to deliver 350,000 ctpa.

Petra's current mine plan for Williamson has a life extending to 2033, but given that the Mwadui kimberlite hosts a major resource of 33.1 Mcts, there is potential to extend the Life of Mine (LOM) considerably.

A decision was taken by management in 2015 to carry out plant modifications at Williamson in order to improve throughput and diamond liberation. This is a particularly relevant strategy at this lower grade operation and the modifications are planned to enable the mine to reach throughput of 5 Mtpa by the year 2018 at a grade of circa 7 cpht previously guided circa 6 cpht. Such an increase in ROM grade, partially offset by a finer diamond size population, is expected to yield a 7 to 10 per cent increase in revenue per tonne.

The plant enhancements will include the introduction of an additional crusher circuit and two autogenous mills, with construction commencing in 2016 and commissioning of the crusher planned for 2016 and installation and commissioning of the two autogenous mills planned for first half 2017.

The ROM throughput is planned at 3.8 Mt during 2016, lower than previous guidance of 4.5 Mt due to downtime associated with the aforementioned plant modifications. Capex of 16.2 million US dollars for the Year 8.9 million US dollars in 2014 was in line with expectations.