WITH final shipments of underground copper, zinc and lead from KBL Mining’s Mineral Hill project in the Central West of New South Wales made in late August, the plant has started processing ore from the Pearse open cut mine. Head grades from Pearse are averaging between 6 and 7 grams/tonne gold and 40 to 70 grams/tonne silver. A plus 50 grams/tonne concentrate will be produced and regularly shipped overseas.
In early September the company said stripping of Pearse open cut over the previous 10 weeks had been a feat for management. It said when the project began 14 weeks earlier there was significant preparation to make and much overburden to be moved.
“More than 600,000 tonnes of waste has been moved and we have hit the top of the sulphide ore body, with more than 8000 tonnes of ore on the plant stockpiles and with the next exposed bench in the pit providing at least a further 30,000 tonnes of ore. The mill will be kept full at all times.”
Initial indications were that Pearse ore being fed through the Mineral Hill process was performing in line with recent optimization test work.
KBL said that upgrades to the existing flotation circuit to allow multi-element processing were nearing completion in early September. However, to further enhance gold processing throughput, new Outotec OK16 cells were being installed and commissioned.
The expansion of the flotation plant will double the ore residence time of the processing facility and bring a measure of improved efficiency. As such, all flotation cells will be dedicated to the processing of gold and silver ore during the Pearse open cut stage.
When KBL returns to processing base metals, the three dedicated flotation circuits within the plant will allow for greater flexibility while processing copper/gold, lead and zinc rich ore.
With underground activities KBL has reduced the mine contractor to 120 metres a month of capital development opening up the down dip extent of the Southern Ore Zone and additional diamond drilling platforms.
In early September development on the decline has reached the 990 level, which was the deepest mined elevation at Mineral Hill to that time. KBL said costs associated with underground mining would reduce by 60% from September as there was no requirement for production from underground, allowing a reduction of fleet and manning. “This development secures the longer term production profile for Mineral Hill.”