Aim-listed Firestone Diamonds' share price on the LSE fell by nearly 28% on Friday after it announced that power supply issues had disrupted production at its 75%-owned Liqhobong diamond mine, in Lesotho.
The mine receives its electricity from the Muela hydropower station (MHS), which is owned by the Lesotho Electricity Company (LEC). The power station is located at the Katse dam, which is part of the Lesotho Highlands Water Project (LHWP).
The Lesotho Highlands Development Authority last month announced that it would shut down the LHWP water transfer and delivery, as well as associated systems, for scheduled maintenance during October and November.
The MHS is also undergoing scheduled maintenance.
Firestone on Friday said South African power utility Eskom was expected to provide electricity to offset the interruption in supply by the MHS.
"Since then, the mine experienced unexpected voltage fluctuations that caused the drives of the plant equipment to trip and, as a result, operations have been severely disrupted.
"Management is addressing the issue urgently with the LEC and Eskom, and will provide further updates in due course," it said.