Anax testing yields strong Sulphur Springs copper and zinc recoveries

Anax Metals’ heap leach testing of Develop Global’s Sulphur Springs ore yields recoveries of up to 95% copper and 99% zinc
High zinc recoveries could unlock significant value for the JV through zinc sulphate production
Acid produced by bioleaching process could be used to leach other acid consuming ores
JV to carry out column leach tests, which will be combined with bench-scale test results to underpin scoping study

Special Report: Anax Metals and Develop Global have received a big boost to their plan to build the latter’s Sulphur Springs zinc-copper project after testing achieved recoveries of up to 95% copper and 99% zinc.

The two companies have an agreement in place to assess the feasibility of treating high-grade oxide and transitional ore from Develop Global’s (ASX:DVP) wholly-owned Sulphur Spring project using the fully permitted existing heap leach facility at their Whim Creek joint venture project.

The Whim Creek and Sulphur Springs projects. Pic: Anax Metals

Anax Metals (ASX:ANX) had acquired an 80% interest in Whim Creek – a historical mine about 120km southwest of Port Hedland in WA’s Pilbara region that produced about 15,000tpa of copper cathode in the mid-2000s – from DVP in its previous guise as Venturex Resources back in 2020.

Since then, it has advanced a restart of the project by completing exploration, resource development and a definitive feasibility study in April 2023 that outlined a modest capital cost of $71m to bring the mine back into production at a rate of 10,000-12,000tpa of copper equivalent metal at an all in sustaining cost of just US$2.23/lb copper.

Under a recent update, this was found to be capable of generating $520 million in free cash over a mine life of eight years along with pre-tax NPV of $357m and IRR of 74%.

It also plans to refurbish the heap leach facility at a modest cost to produce copper cathode and zinc sulphate in the second year of operation.

More recently, ANX unveiled plans to use Whim Creek to underpin plans to build a regional hub that would offer owners of smaller and otherwise uneconomical deposits the opportunity to monetise their assets, signing up GreenTech Metals as a potential partner in this endeavour.

Stirred tank leaching results. Pic: Anax Metals

“Excellent amenability” to heap leach process

ANX has now found that oxide and transitional ores from Sulphur Springs have excellent leaching amenability to the Whim Creek heap leach process.

This included the use of Whim Creek bacteria adapted specifically for Sulphur Springs ore to enhance the leaching process.

The bench-scale tests on high-grade transitional and oxide ore samples achieved copper recoveries of between 80% and 95% while transitional ore rich in zinc yielded recoveries of between 95% and 99%.

ANX noted that the high zinc recoveries could unlock significant value for the JV through zinc sulphate production while the production of acid through the bioleaching process is potentially another valuable by-product that could be used to leach other acid consuming ores.

“The Anax team has applied the considerable knowledge and learnings, including from the Whim Creek heap leach programme over the last three years, to deliver outstanding outcomes in this preliminary round of test work,” ANX managing director Geoff Laing said.

“Heap leaching of copper oxide and transitional ores is commonly practiced, and the Sulphur Springs ore has demonstrated excellent amenability to the process conditions we have applied.

“We are excited to have demonstrated the excellent response of zinc dissolution to the process as this may facilitate the production of zinc sulphate, a key additive to fertilisers.”

Next steps

With previous test work completed by ANX demonstrating that leaching recoveries in column tests correlated well with recoveries in bench-scale leaching test work, the two companies are now evaluating the use of column leach tests on Sulphur Springs ore with a larger particle size.

Results of the leaching test work will underpin the scoping study that has been initiated by the two companies.

This article was developed in collaboration with Anax Metals, a Stockhead advertiser at the time of publishing.

This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.