Annual output at the Williamson diamond mine in Tanzania ‒ owned by leading independent diamond mining group Petra Diamonds ‒ is expected to soar by over 40 % in the next three years to 3.6t of ore containing 216,000 carats.

The mine, renowned for its high value ‘bubblegum’ pink diamonds is located at Mwadui, in the Shinyanga area; it is expected to produce 2.5Mt this year following the completion and commencement of its phase-one project in Q4 of 2012, reports allAfrica.com.

Petra Diamonds says in its latest trade update that Williamson produced 150,342 carats in the year ended April 2013, as opposed to the previous year's 42, 855 carats, following the successful start-up of the newly rebuilt treatment plant. Petra owns 75% of Williamson while the government controls the remaining 25%.

Also, contract mining of alluvial diamonds is expected to contribute 14,000 carats in FY2013, with annual review of production levels thereafter. Alluvials are deposits of diamonds that are found in riverbeds, the seabed or the shoreline.

The mine lifespan has been extended to 18 years with a major resource base of 39.6 million carats. Williamson is an open pit operation, based on the mining of the 146 hectare Mwadui kimberlite.

Over the past two years, Petra has been implementing the phase one development programme, which involved substantial reconstruction of existing plant and major pit reshaping work.

As far as costs are concerned, the company said, it had achieved a cost of US$18/t during the initial start-up, amid anticipation to reduce this to US$11/t in 2013.

"In the long run, operating costs are expected to drop to US$9.5/t from 2014 and US$ 9/t from 2017 onwards because of increased tonnages diluting the mine's fixed cost base,” Petra said. The mine's Phase-Two expansion project, which was initially planned to take the mine to10Mtpa, is currently on hold, due to inadequate electricity and water supply.