(IDEX Online) - A power outage halted ore treatment at Firestone's Liqhobong, mine in Lesotho, for almost a month and cost $4.6 million, the company said today.
The disruption increased costs in Q2 - $14.90 per tonne treated compared with $10.32 in Q1, according to the quarterly operations update.
The number of tonnes treated was reduced to 668,120 (Q1: 963,986 tonnes) and diamond recoveries were down to 138,000 carats (Q1: 201,091 carats).
The mine suffered unexpected and damaging voltage fluctuations when its main power supplier, the Muela Hydropower Station, shut down for two months of planned maintenance.
As a result, all treatment of ore was halted from 1 to 16 October 2019. It resumed at around 90% capacity when diesel generators were sourced from South Africa and grid power was restored on 1 December.
The company has revised down its 2020 forecasts, suggesting diamond recoveries will fall to between 720,000 and 750,000 carats (previously 820,000 to 870,000 carats) and tonnes of treated ore from, 3.3 and 3.6 million (previously between 3.6 and 3.8 mt).
CEO Paul Bosma said: "The unexpected power disruption had a devastating impact on production and revenue generation. The team however, did well to salvage the situation by procuring and installing generators from South Africa in record time to allow for operations to recommence.
"Due to the production setback and continued lacklustre market conditions, the Board has decided that it is imperative that it does all it can to reduce costs in order to survive the prolonged downturn."