Isabel Barton unlocks Arizona’s copper potential

Beneath Arizona copper mine deposits lies chalcopyrite – the most plentiful source of copper in the state and around the world. But recovering copper from chalcopyrite requires considerable effort and cost. Streamlining recovery methods could unlock more of this resource for power systems and other urgent needs. 

Phoenix-based mining company Freeport-McMoRan is funding a $1.2 million University of Arizona research effort to improve the efficiency and sustainability of chalcopyrite recovery. Isabel Barton, associate professor in the U of A School of Mining Engineering and Mineral Resources, leads the project.

“The more you rely on electrical parts or systems, the more copper you need,” Barton said. “If we're going to supply enough copper for the world, we have to be able to process chalcopyrite.” 

Copper is a major driver of Arizona’s economy, with the state producing 70% of the nation’s supply, according to the U.S. Geological Survey. A U of A report indicates that Freeport-McMoRan produces roughly 80% of Arizona’s copper ore.  

The project began in 2023 and is expected to conclude in two years. The researchers are investigating why chalcopyrite dissolves inconsistently during leaching, the chemical process that pulls copper from rock. The team aims to improve extraction methods and copper yields by analyzing how chalcopyrite’s composition and structure impact leaching. 

These advances could reduce reliance on overseas processing. As advanced computing increases electricity demand and countries worldwide expand power capacity, pressure is mounting to upgrade transmission systems – driving demand for the copper needed to move energy efficiently at scale. 

In addition to carrying electricity for power systems, copper is used for plumbing, roofing, climate control, industrial machinery and electric vehicle components. 

“Copper powers our whole lives. It’s the element we use the most in daily life, but it ends up being taken for granted,” said Sarah Patterson, a mining and geological engineering doctoral student collaborating with Barton.  

Making a mark in academia, industry 

Heap leaching is a common way to extract copper from near-surface ores such as malachite and azurite. For these deposits, miners crush the rock and spread it across large, lined pads to prevent contamination. A sulfuric acid solution dissolves the copper-bearing minerals as it filters downward. The metal-rich solution is then collected and purified, producing usable copper. Dissolving the metal directly into a liquid solution avoids more energy-intensive methods and can recover large amounts of copper.  

But unlike these soft surface ores, chalcopyrite does not dissolve well in sulfuric acid, making it a poor match for heap leaching. 

“It is very insoluble. If you try to leach it by conventional methods, you'll get somewhere between 0 and about 20% recovery,” Barton said. 

Since leaching becomes inefficient at deeper levels of the deposit, miners change methods as they reach the chalcopyrite level. The rock is crushed, ground and processed to produce a concentrate, which is then sent to a smelter – often in China – for high-temperature extraction of the metal. The process is costly and environmentally demanding. Some chalcopyrite, found to be too resistant to break down, eventually ends up in tailings or waste piles.  

These economic and social costs are driving research that will help Freeport-McMoRan adapt and tailor heap leaching methods for different chalcopyrite ore types – improving local copper recovery while reducing waste and overall processing costs. Achieving this, however, will require a deeper understanding of the mineral’s complex behavior under different conditions.  

“There's enormous literature and decades of research, and yet we haven't actually established a lot of the basic phenomena,” Barton said.

At this stage, the collaborators are assembling a large dataset on chalcopyrite from sites and geologic settings around the world, cataloging major and trace element composition and other characteristics tied to how electrons move through the mineral. 

“When you remove an electron, the structure has to adjust in a way that kicks the copper into the solution,” Barton said. 

In addition to analyzing and logging natural samples, the researchers are synthesizing chalcopyrite in the lab with carefully controlled compositions. By creating these lab-grown samples, they can better isolate the effects of specific trace elements and mineral combinations. 

“Between the dataset and our synthetic studies, I think we will be able to have a much clearer idea of what factors influence chalcopyrite leaching, in which ways,” Barton said.  

The collaboration has already provided interesting insights, said Mitchell Catling, Freeport-McMoRan’s manager of metallurgy. 

“The research is informing our ‘Leach to the Last Drop’ initiative, aimed at extracting more copper from existing stockpiles, by improving knowledge of sulfide leaching and the impact of natural ore impurities,” he said. 

Patterson worked on the project since its inception, beginning while earning her U of A master’s degree. She believes dedicating years to this detailed project is valuable preparation for a career as a research scientist. It’s helping her connect laboratory analyses to broader economic and industry impacts. 

“It's really boiling it down to micro characteristics that have macro consequences,” she said. “Working on that scale is rewarding, and it feels direct.”