At Rusina Mining’s (LSE:RMLA) Acoje project on Luzon island, European Nickel are spending US$10 million to earn 40% project share by conducting trials and studies on the Acoje laterites, where a recently published prefeasibility study has confirmed a JORC indicated resource of 30.8 million tonnes at 1.12% nickel and 0.05% cobalt.
At Acoje, both limonite and saprolite will be mined, and will be blended and agglomerated before stacking on the heaps. The agglomeration of the soft, wet limonite with the harder saprolite produces a mixed ore which is stable enough to be stacked and allows good percolation of the leaching agent. The saprolite also leaches very quickly, with some 80-90% metals recovery within only 10 days, and offsets the slow leaching characteristics of the limonite. Further modifications to deal with the “wet” ores involve covering the heaps to protect them from rain, and the use of “dynamic” heaps - rather than a single multistack heap as at Caldag. As each heap is exhausted of metals, the spent ore will be neutralised and removed for eventual use as back-fill in mined-out out areas, and fresh ore will be loaded on to the vacant heap.
The PFS envisages a 10 year mine life from the existing indicated resource – mining the inferred resources could add another 13 years – with an output of 24,500 tonnes of nickel and 932 tonnes of cobalt pa. Cash costs are estimated at US$3.10 per lb of nickel (at a nickel price of US$6.00 per lb), net of by‑products and including a refining charge of 25% of the nickel price and a cobalt price of US$10.00 per lb. Capex is estimated at US$498 million, including infrastructure and working capital, giving a capital intensity cost of US$7.76 per lb - highly competitive when compared to HPAL projects. The project has a post‑tax 10% NPV of US$375 million and a three year payback period after commissioning. A demonstration plant will be constructed shortly as part of the full feasibility study, which is due for completion in 2010.
