The Asia Miner

JAN-FEB 2018

The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region

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66 | ASIA Miner | Volume 15 • Issue 1 | 2018 Australia Copper There are two main options to recover cobalt from the cobaltian pyrite – leaching, including acid leach or bacterial oxidation; and roasting and acid plants, which also produce by-product sulphuric acid and iron ore. Chris Giles says the roasting alternative produces the best rev- enue stream but is capital intensive while leaching is less capital intensive and should produce saleable cobalt salts. Basic leaching experiments show that an extremely acid solution, which can be generated from oxidation of the ore, is moderately effective in leach- ing the pyrite and releasing cobalt. Havilah's pre-feasibility study will include: • Completion of a detailed mining plan and design to initially mine the high-grade massive sulphide south pod; • Design and costing of a standard copper concentrator to recov- er copper sulphide concentrate and pyrite concentrate; • Leaching tests for cobaltian pyrite to determine the best recov- ery method; and • Studies on roaster and acid plant design and costing to deter- mine the feasibility of roasting massive sulphide ore. • "Another plus is that Mutooroo is only 40 minutes outside Bro- ken Hill," he says, "which means no need for a camp as it will be a convenient bus trip at the start and end of shifts, and it is only 16km from the rail line, making it easy for mine logistics." Portia's golden future is in copper Portia has seen Havilah become a gold producer after years of ex- ploring a suite of projects and the transformation is primarily due to a unique partnership with CMC. The arrangement with the Broken Hill-based company headed by Steve Radford has seen CMC remove 70 metres of overburden, set up a camp and mine infra- structure, mine the gold-bearing ore, and assist with optimising the processing facilities. For this CMC receives a half share of revenue from the operation. The progress from mining of first gold-bearing ore in early March 2016, to completion of the processing plant in April and first gold pour in May was achieved ahead of schedule. There have been challenges, including pit wall stability issues in the soft overburden, periods of heavy rainfall, groundwater inflows and processing plant issues, but Chris Giles says these have all been overcome by the CMC and Havilah partnership. Mining of the originally defined deposit was completed by the end of 2016 but further ore in the underlying bedrock and further miner- alisation in the southern part of the pit and beyond, will see mining continue into 2018. Portia continues to return spectacular grades in the floor of the open pit including 6 metres at 34.84 g/t gold, 3 metres at 29.37 g/t, 6 metres at 17.95 g/t, and 10 metres at 8.62 g/t, indicating further life yet. However, the long-term future lies in the much larger adjoining North Portia copper-gold open pit, planning for which is well ad- vanced by CMC. At a minimum, this project would add another six years of mining on the Portia lease with a 1 million tonne gold cap running at 1.5 g/t and an underlying 4 million tonne enriched copper-gold zone grading 1.2 % copper equivalent captured in the initial open pit design. Beneath this lies an impressive grade primary sulphide ore body, which is not included in the six-year mining plan. The Portia gold mining exercise, while a modest operation by nor- mal standards, has been of immense value in solving many of the unknown issues around mining in this area, and will greatly reduce the mining risk for North Portia and then Kalkaroo. In addition, much of the infrastructure built for Portia, including the processing plant, will be utilised for processing North Portia ore. Chris Giles says that even the Portia open pit, once completed and allowed to fill with groundwater, will be an asset in providing a reservoir of processing water and a place to safely dispose of sulphide tailings and waste material. Havilah's projects lie in South Australia's northeast, not far from the rail line that links Sydney with Perth.

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