The Damang operation in Ghana was facing “orderly closure”, but a new approach to crushing, coupled with intense exploration, has given the Gold Fields mine a new growth horizon.
The life-of-mine outlook for Damang now extends to 2019 and the dream is to extend that to 2025.
The saviour is a secondary crushing plant that paid for the capital outlay of $11,7-million in only eight months.
Until then, the mine life was based on the availability of oxide ore, which was depleting.
The operating margin outlook is up at 44% from 26% three years ago, on a production outlook of economic aspects of mining phosphate in south africa240 000 oz of gold a year, up from the current 200 000 oz.
The secondary crusher enabled the mine to harden its blend, effectively increasing the proportion of “fresh” hard rock of higher grade.
The secondary crushing process now allows for hardeconomic aspects of mining phosphate in south africa rock to predominate at a proportion of 95% of the total input material, with the oxide input declining to 5%.
Over the life-of-mine, the operation will run out of oxide material completely.
The hardening of the blend through the increase of “fresh” hamay dan bang tai almexrd rock has increased the overall grade from 1,3 g/t to 1,6 g/t.
The secondary crusher has also taken the pressure off the primary crusher by doing some of its work.
Exploration towards a “super pit” will ensure a consistent supply of higher-grade hard, “fresh” ore.
The resource is estimated at 4,3-million ounces of gold and the reserves are estimated at 1,8-million ounces.
Damang is currently operating in three different pits, with the Damang Pit Cut Back the source of the hard feed at a grade of 2,2 g/t.
“We have the hardest rock in Ghana,” Damang GM Alfred Baku tells Mining Weekly.
Because of the hardness, Baku adds, Damang has resorted to the use of three times more-expensive electronic detonation, which provides the necessary fragmentation and control.
“You don’t get fly rocks and a lot of overbreak. The floor is quite even and tyre life is increased,” he says.
The ore is processed in a carbon-in-leach plant.
Once in steady state, the cash costs are expected to be $590/oz and the notional ‘all in’ cash costs $690/oz.
Because power supply was a “huge” problem in 2005, the mine has 24 diesel-driven generators able to supply 17,5 MW in the case of power outages on the lower-cost national grid.
The generator sets run at a cost of US28c/kWh to US30c/kWh compared with the US10c/kWh cost of the national grid.
The cost of
power, already one of the main drivers of costs, may rise further as the national grid tariff may rise to US15c/kWh or even US2Oc/kWh.