Global gold-mining company Harmony Gold’s Kusasalethu mine, formerly the Elandsrand mine, near Carleton-ville, in the North West province, aims to produce 200 000 oz of gold in the company’s 2011 financial year, the company reports in its September 30 first-quarter review of the mine.
The company plans to mill 1,3-million tons of ore at the mine with an average grade of 5,16 g/t of gold. Further, once levels 109 and 113 have come into production in July 2013, gold output is expected to rise to more than 300 000 oz/y.
The planned ramp-up of production at Kusasalethu, a key part of the company’s plans for the mine’s 28-year life span, is continuing and the grade of ore mined is expected to increase gradually to 6,45 g/t of gold until full production in 2013. More mining will take place in the high-grade facies, where the Elsburg reef crops out against the Ventersdorp contact reef, causing localised enrichment on the western side of the company’s mining lease area.
Further, the deepening project on the mine, which is 95% complete, involves the extension of the subvertical shafts to access the deeper parts of the Ventersdorp contact reef to a depth of 3 600 m. The shaft infrastructure is in place and work over the next two years will focus mainly on the provision of sufficient cooling and ventilation to the new mine areas, the company says.
Volumes milled increased by 8% to over one-million tons, but a 7% decline in grade means that the 175 029 oz/y of gold produced was only fractionally higher than the 174 321 oz of gold produced in the 2009 financial year. Currently, 60% of Kusasalethu’s production is from areas below the 100 level, which means that it comes from the new areas, and 40% is produced from the older parts of the mine.
“Underperformance on square metres broken was the mine’s biggest challenge in the 2010 financial year. Scaling in the main reef and waste-ore pass systems resulted in blockages in both systems, which contributed to waste dilution and resulted in the lower recovered grade during the year,” the review states.
The mine will separate reef ore and waste rock and is working to remove the blockage in the waste pass system between the old mine (above the 100 level) and the new mine (below the 100 level). Once the blockage has been removed, waste rock and reef ore will again be tipped into one ore pass system to accommodate the rehabilitation of both systems. This will dilute the recovered grade but will not affect gold production, the company says.
However, productivity is currently at 84 g for each twenty-foot equivalent con- tainer (TEC) and is a concern to the company. Plans are in place to increase productivity to 158 g/TEC in 2013, after peak production has been achieved, by increasing volumes from the new mine areas where the mining opera- tion is more efficient.
Meanwhile, the mine is continuing its focus on creating a safe working environment and overall safety performance improved in the 2010 financial year.
“Seismicity continues to be a risk for the operation and measures to improve the quality of the preconditioning at the stope face have been implemented to reduce the possibility of face ejection during small, volatile seismic events,” the company concludes.
Mining at Kusasalethu uses conventional mining methods in a sequential grid layout. Ore mined is treated at the Kusasalethu plant. At the end of June 2009, the mine reported ore reserves of 7,541-million ounces and mineral resources of 11,556-million ounces.