Modern Mining June 2015

MINING News

RHA tungsten project produces its first concentrates

AIM-quoted Premier African Minerals Limited says that the first concentrates have been produced at its flagship RHA tungsten project in Zimbabwe. The proj- ect is located in the Kamativi tin belt of north-western Zimbabwe and Premier is planning two stages of development – a first phase, low capex (US$4,8 million) open pit, which provides an 18-month life of mine, followed by an undergroundmine (capex estimate – US$14,7 million) based on mechanised long-hole open stoping. The open-pit annual production will be 96 000 t (ROM) while the underground production rate will be between 192 000 and 288 000 t (ROM). The production of the concentrates fol- lows hard on the heels of the delivery of the process plant to the site in May. The plant was designed and manufactured by Appropriate Process Technologies (APT) of Johannesburg, who were also responsible for assembly on site and commissioning. The earthworks and civil works programme was successfully fast tracked to ensure that the site was ready for offloading of the plant. Development of the open-pit mining

Trucks carrying the process plant arrive on site at the RHA tungsten project on 22 May (photo: Premier African Minerals).

area remains on schedule, with waste strip- ping underway and run of mine ore being stockpiled. According to Premier, visible mineralisation continues to confirm the geological model. The process plant is designed to meet a throughput of 16 t/h or 8 000 tonnes per month and achieve a wolframite recov- ery of 82,8 %. The stated production rate excludes any consideration of a pre-con-

centration circuit which, if implemented in future, could increase the plant through- put fivefold at a 20 % recovery loss as determined in the metallurgical test work announced on 10 September 2014. Intermittent small scale mining has been conducted at RHA and the adjacent Tung mine (which Premier has an option to acquire) 5 km away. Between 1931 and 1979 the mines jointly produced 1 247 tonnes of WO 3 in wolframite concentrate at a reported average concentrate grade of 65 %WO 3 , i.e., approximately 1 919 tonnes of wolframite concentrates. Infrastructure from the historic mining includes a vertical shaft, numerous adits and some under- ground development. Premier announced in March this year that it had completed an off-take agree- ment with Noble Resources International for the sale of wolframite concentrates from the mine. Under the agreement, Premier will supply 500 tonnes of concen- trate over an anticipated initial six-month period whereafter Noble will have a right of first refusal of all future concentrates provided it matches terms offered by other parties. Concentrates are sold in metric ton units (‘mtu’) where one mtu is 10 kg of tungsten trioxide (WO 3 ) contained in a concentrate at a declared percentage, normally 60 % to 65 % being a common reference point. Premier anticipates pro- duction during the open-pit phase of the RHA mine of approximately 5 800 mtu per month of WO 3 contained in a concentrate at an average grade of 63 %. 

Open-pit operations at the project site (photo: Premier African Minerals).

4  MODERN MINING  June 2015