US-based copper developer and near-term producer, Arizona Sonoran Copper Company Inc, has entered into a one-year exclusivity period with Nuton™, a Rio Tinto Venture that, at its core, is a portfolio of proprietary copper leach related technologies and capability.

The exclusivity was triggered by successfully modelling the Cactus and Parks/Salyer ore samples and achieving the previously contemplated indicative metallurgical recoveries of at least 72% (copper recovery to cathode), which included chalcopyrite, under an investor rights agreement, Arizona Sonoran said.

Nuton will continue to test the application of its copper heap-leach related technology to the primary sulphide component of the Cactus Mine and Parks/Salyer Projects, in Arizona, through column leaching and scoping out capital and operating costs and design parameters, it added.

The sulphide potential is not included in the 2021 Cactus preliminary economic assessment, which contemplated a simple heap leach and SX-EW operation over an 18-year mine life, producing an average of 28,000 t/y of LME Grade A copper cathode.

Within the current Cactus project resource base is a primary sulphide mineral resource of 77.9 million short tons (70.7 Mt) at 0.35% CuT (indicated) and 111.2 million short tons at 0.35% CuT (inferred).

George Ogilvie, Arizona Sonoran President and CEO, said: “The Nuton preliminary work results indicate optionality for unlocking the substantial primary resource at Cactus, which is currently stranded at the bottom of the pit. Although we are in the early stages of testing chalcopyrite recoverability on an economic basis, we are encouraged by the initial results and the significant potential to continue building scale at Cactus and potentially at Parks/Salyer in the longer term.”

The preliminary metallurgical testing program covered ore sample selection, preparation and mineralogical characterisation to produce CFD modelling results providing early-stage indicative recoveries in respect of various ore types and specifically the chalcopyrite ore at Cactus. Further test work underway covers test column leaching and scoping out capital and operating costs and design parameters, the company said.

Nuton is an innovative new venture that aims to help grow Rio Tinto’s copper business. At its core is a portfolio of proprietary copper leach related technologies and capability – a product of almost 30 years of research and development. The Nuton technologies offer the potential to economically unlock known low-grade copper sulphide resources, copper bearing waste and tailings, and achieve higher copper recoveries on oxide and transitional material, allowing for a significantly increased copper production outcome, according to Rio. One of the key differentiators of Nuton is the potential to deliver leading environmental performance, including more efficient water usage, lower carbon emissions, and the ability to reclaim mine sites by reprocessing mine waste, it claims.