Mining group Petra Diamonds reports that it is looking to extend the life of its Williamson diamond mine in Tanzania’s Shinyanga region, from 20 years to more than 50 years, following the comple-tion of the first phase of its development programme.

The programme, which involved a substantial rebuild of the existing plant and major pit reshaping work, revealed a major resource of 39.4-million carats on the Mwadui kimberlite upon which the mine is based.

“Williamson is the world’s largest economic kimberlite by surface area at 146 ha in size. It is Tanzania’s only important diamond producer and despite having been operated continuously since 1940, the pit is only 90 m at its deepest point owing to the large size of the deposit,” the company states.

Petra is now implementing an expansion plan to increase production from about 160 000 ct/y in the 2013 financial year to about 300 000 ct/y by the 2017 financial year.

According to the company’s website, it plans to increase run-of-mine produc-tion to about 3.6-million tons in the 2014 financial year, before steadily increasing to about 5-million tons a year by the 2017 financial year, which at a grade of 6 ct for every hundred tons, will deliver 300 000 ct. This is an increase from previous guidance of 3.6-million tons a year by 2017.

“These improvements will be as a result of a focus on the plant design to deliver energy efficiency and water recovery circuit improve-ments, resulting in the ability to increase throughput,” the company states, adding that it will continue to consider approaches to increase production beyond 5-million tons a year.

An expansion plan above this level is dependent upon security of appropriate elec-tricity and water supply,” it notes.

An interim management statement issued by the company, which owns a 75% stake at the mine, with the Tanzanian government owning the remaining 25%, states that diamond production increased by 471% from July 2012 to March this year. The pro-duction has increased from 21 570 ct (July 2011 – March 2012) to 123 243 ct (July 2012 – March 2013).

The mine produces 5.6 ct for every 100 t, which remains in line with guidance of 5.5 ct for every 100 t backed by the commissioning of the rebuilt treatment plant. The mine, which underwent extensive development to increase its capacity last year, also saw its treated tonnage increase by 436% from 423 131 t to 2 266 113 t in the said nine months.

The mine’s second phase expansion project, which was initially planned to increase its production to 10-million tons a year, is currently on hold, though, Petra continues to consider approaches to further significantly increase production beyond 3.6-million tons a year.

Petra Diamonds is an independent dia-mond mining group and an increasingly important supplier of rough diamonds to the international market. The company has interests in eight producing mines; seven in South Africa, namely Finsch, Cullinan, Koffiefontein, Kimberley Underground, Helam, Sedibeng and Star mines.