- 01Cobre buys 150,000t of ENAMI feed at ~US$9/t.
- 02Pads and ponds targeted for copper recovery.
- 03Feed mix aims to lift plant use as mining expands.
Cobre (ASX: CBE) has secured approximately 150,000 tonnes of copper-bearing material for its Sierra Atacama operation in Chile while launching two recovery initiatives using historical material already on site.
The purchase from Empresa Nacional de Minería (ENAMI) covers previously crushed and leached copper oxide material grading about 0.65% copper at an estimated delivered cost of US$9 per tonne.
At the same time, the miner has begun recovering copper from historical solution ponds and re-leaching older stacked pads to supply its existing processing plant.
The three feed sources are intended to lift plant utilisation as underground mining ramps up and Cobre prepares its planned open-pit expansion.
Regional Feed Flexibility
The ENAMI stockpile lies within 55 kilometres by road of Sierra Atacama, allowing Cobre to use nearby material rather than rely exclusively on newly mined ore.
Cobre expects to transport around 30,000t each month and blend the material with ore from its underground operation.
Metallurgical column tests achieved 58% copper recovery, although planning assumes a more conservative recovery of approximately 50% at industrial scale.
The ore has already been crushed and leached, reducing the preparation needed before it enters Sierra Atacama’s existing leach and solvent extraction–electrowinning (SX-EW) infrastructure.
The acquisition complements a broader strategy to establish the operation as a regional processing hub, with relatively low expected acid requirements particularly relevant amid high acid prices.
Old Pads Yield Fresh Copper
Historical leach pads provide another potential feed stream because earlier operators recovered only about 50–55% of their copper, compared with Cobre’s current recovery rates of 72–82%.
Those older pads were stacked to heights of 30 metres, while Cobre now uses finer crushing, lower stacks, and dynamic leaching to improve recovery.
Preliminary volumetric modelling suggests the pads could contain more than 10Mt of material, but their tonnage and grade have not been established to the standard of a reportable mineral resource.
Initial surface irrigation using recycled intermediate leach solution has generated pregnant leach solution (PLS) containing approximately 2 grams per litre of copper, which is being fed into the operating circuit.
Cobre plans to refine irrigation rates and solution chemistry before assessing other approaches, including injection leaching, during the December quarter.
Pond Sediment Supply
A separate recovery program is targeting copper-rich sulphate precipitates and sediments accumulated in historical lixiviant ponds at Sierra Atacama, where workers have begun circulating water through the deposits to dissolve soluble copper before filtering the resulting solution and transferring it into the existing PLS circuit.
This route uses installed facilities and is expected to require minimal additional capital, with first copper production from the pond program targeted before the quarter ends.
“Securing approximately 150,000t of low-cost ENAMI material, while simultaneously recovering copper from historical ponds and re-leaching historical pads, gives us three potential sources of incremental copper that can utilise infrastructure already in place,” chief executive officer Adam Wooldridge said.
“These initiatives have been identified and moved rapidly into implementation by the Sierra Atacama metallurgy team, and have the potential to support increased copper production as we ramp up underground mining and progress toward open-pit operations.”
The initiatives remain at different stages of delivery, with the purchased stockpile providing a defined supplementary feed source while further work tests how much copper the historical pads and ponds can economically yield.
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