Dump leaching plans will substantially increase reserves at Aur Resources’ (AUR-T) Andacollo mine in northern Chile.
The reserve estimate at Andacollo rises to 32.3 million tonnes grading 0.58% copper, up from a figure of 17.2 million tonnes averaging 0.71% copper. Both estimates are for the 2004 year-end, and include about 4.2 million tonnes grading 0.71% copper scheduled for mining in 2005.
The new resources brought into reserves mainly consist of 12.5 million tonnes of low-grade material that can be treated by dump leaching. The grade of the new material brought into reserve averages 0.38% copper — hence the sharp decrease in the average grade of the Andacollo reserve.
About 73% of the copper in the dump-leachable reserve is acid-soluble or cyanide-soluble, compared with 87% of the copper in the heap-leachable reserves.
Adding a dump-leach plant is to cost US$4.5 million. Economic modelling studies show a US$43.7-million increase in the mine’s net present value with the increased production, based on US$1.20-per-lb. copper (US$2,650 per tonne) for most of the remaining mine life and an 8% discount rate.
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