South32’s Hermosa Project sets the bar high for new mining developments

The United States has set bold decarbonization targets to reduce greenhouse-gas emissions and compete in the global economy. South32, a global metals and mining company headquartered in Perth, Australia, is contributing to this mission with its Hermosa project, located in Southern Arizona’s historic mining district of the Patagonia Mountains. As of 2025, this is one of the only advanced mine development projects in the United States capable of producing two federally designated critical minerals — manganese and zinc — essential for powering the nation’s clean energy future. The project will also produce a smaller amount of silver, with the first zinc production expected to start in 2027. Through the Hermosa project’s substantial production of these critical minerals, South32 aims to strengthen the domestic supply chain and help reduce U.S. reliance on foreign nations. Manganese, one of the projects’ target metals, is vital for electric-vehicle batteries, steel and the U.S. military, while zinc is crucial for battery storage, solar panels, wind turbines and other infrastructure. Demand for battery-grade manganese is expected to grow 15-fold from 2020 to 2031, according to research by E Source. Currently, the United States produces only six percent of the world’s zinc, but Hermosa aims to increase these numbers. “Manganese hasn’t been mined in North America since the 1970s, so this is really important to national security and the climate-change goals of the nation,” said Skylie Estep, human resource director for North America at South32. Since December 2023, the Hermosa project has seen significant advancements, including a final investment decision for $2.16 billion, the largest private investment in Southern Arizona’s history, to develop the zinc-lead-silver deposit, and two federal grants totaling $186 million. These grants are for their manganese project: a $20 million grant from the U.S. Department of Defense and a $166 million grant from the U.S. Department of Energy. “The Department of Energy grant is to ensure that we’re able to create supply chains for manganese, reducing reliance on foreign supply chains for the manganese deposit,” said Estep. “The Department of Defense grant is to drive the decline to access the ore body so that we’re able to access the minerals needed for national security at a sooner pace than maybe we were anticipating as we go through prefeasibility study activities.” Not only does South32’s production and discovery of manganese and zinc deposits make it unique, but also its small footprint. At a size of only 750 acres, a fraction of the land occupied by many open-pit mines, Hermosa is significantly smaller and will use advanced equipment for safer operations. This approach significantly reduces surface disruption, helping preserve the natural landscape of Arizona’s Patagonia Mountains. One of the key sustainability measures at Hermosa is its underground mining method, which utilizes long-hole open stopping. This technique allows South32 to manage waste material more effectively by employing paste backfill, where a portion of the extracted material is mixed with cement and returned underground. “We took a really intentional approach to how we will mine at Hermosa,” said Estep. “The first being that we will access the ore body, whether it’s the zinc ore or the manganese ore, through underground mining methods.” Significant capital has been directed toward shaft construction to access zinc ore, with both the main shaft head frame and ventilation shaft head frame now completed. The installation of hoisting equipment for both shafts is also well underway, along with the decline to access manganese ore, setting the stage for the next phase of underground development. These advancements will enable South32 to access the rich manganese and zinc ore bodies. “We’re also progressing a lot of exploration activities, primarily on our flux resource, which is anticipated to be another zinc resource, as well as a peak copper discovery,” said Estep. By reintegrating tailings into the mine, South32 will minimize surface waste storage, reduce land subsidence and enhance structural stability — critical for long-term environmental protection. “We will recycle some of the tailings and put it back underground to reduce surface subsidence, which is really important. The second piece to that is, we will recycle the processing water, allowing us to reduce the tailings footprint through dry stack tailings methods,” said Estep. Water conservation is another defining feature of Hermosa’s sustainability strategy. Open-pit mining in the region traditionally requires immense water consumption, but Hermosa is expected to use 90 percent less water than other mines in the area. The project will use 0.5 gallons of water per pound of metal produced, as opposed to five gallons for other comparable mines. To ensure responsible water usage, South32 invested in in two state-of-the-art water treatment plants, which allows for extensive water recycling and purification. These facilities will help mitigate impacts on local water resources and ensure that surrounding communities and ecosystems are not adversely affected by mining activities. South32 also stared another sustainability commitment- environmental monitoring. transparency. The company has pledged to partner with local third-party public health organizations to conduct regular environmental assessments and openly report findings. This proactive approach ensures accountability and fosters community trust in the company’s mining practices. Along with water conservation and environmental monitoring, South32 is integrating renewable energy solutions into Hermosa’s design. The mine is being developed with the capability to draw power from renewable energy sources and plans to incorporate electric vehicles into its fleet, reducing greenhouse-gas emissions associated with traditional diesel-powered machinery. The project also includes the construction of a remote operating center in Nogales, AZ, called Centro. This facility will allow employees to monitor mining equipment remotely, providing an office-like setting for around 200 full-time employees working over multiple shifts. “Centro enables accessibility for people who may not want to work underground or those with different abilities,” said Estep. “It’s about creating opportunities and keeping employees engaged by offering variety in their work. Additionally, our administration offices will be in Centro, making these jobs more accessible to the local community and reducing commuting challenges.” The mine itself will incorporate autonomous and semiautonomous machinery, reducing human exposure to hazardous environments. Equipment such as automated loaders, haul trucks and drill rigs will be operated remotely, allowing for safer and more precise execution of tasks. While some employees will still be needed underground for tasks like ground control, drilling and equipment maintenance, much of the heavy machinery will be monitored and controlled from Centro. Employees of the Hermosa project will be divided into different subsets, one of which will work both at Centro and at the mine site. The facility’s design incorporates accessibility and inclusivity, offering job opportunities for those historically underrepresented in the mining industry. Regarding the location of Centro, Estep said, “This was an intentional decision made by the organization to ensure that people in the local community have accessibility to really good paying jobs. So, it allows us to design our work a bit different.” In addition to Hermosa’s sustainability aspects, the project also strives to empower its surrounding community. Through certain development approaches, South32 aims to grow the local economy and improve lives in a region with higher-than-average rates of poverty and unemployment. Santa Cruz County, where the project is located, has an unemployment rate of more than 9 percent, with nearly 25 percent of residents living below the poverty line. South32’s Workforce Development Taskforce is creating pathways for local residents to access well-paying jobs, including partnerships with local schools and Santa Cruz Center Provisional College District to offer specialized training programs. “Our purpose really is to help communities realize the full potential of the resources that are in existence in their community,” said Estep. Hermosa has already created 2,381 indirect and induced jobs in Santa Cruz County and 3,465 across Arizona. The average annual earnings for these jobs are $90,000, double the county’s average household income. South32 aims for an 80 percent local workforce goal at peak operations, ensuring downstream economic benefits for the region. The initial zinc-lead-silver construction phase is projected to contribute nearly $1.5 billion to Arizona’s economy and $700 million to Santa Cruz County, generating $32.2 million in local taxes and $61 million in state taxes. The operations phase is expected to add $936 million annually to Arizona’s economy and $709 million to Santa Cruz County, along with $14.9 million in local taxes and $19.3 million in state taxes each year. “We have a really unique opportunity to deliver on every sense of our purpose. And our employees come here because they know that they can do that,” said Estep, regarding South32’s community impact. “When you give someone purpose and connect them to that purpose, I think it sparks excitement. It ties them to their work. It adds to their ‘why’. And feedback that we get consistently is, no matter who you talk to, there is a common thread through everyone’s connection to the purpose.” In just over two years, South32 will begin to extract zinc and silver from the project site. Until then, in terms of getting the equipment ready for production, the organization will continue sinking shafts, completing the zinc concentrator facility and executing lateral development for the underground infrastructure. This includes completing the loading stations, the underground autonomous loop station and the underground crushing and conveyance projects. Concurrently, South32 will continue the development of its workforce programs in partnership with local schools and will continue to staff and train its workforce. By prioritizing sustainability, workforce development and domestic supply-chain resilience, South32’s Hermosa project represents a significant step forward for the U.S. in achieving its domestic mineral supply goals while revitalizing local communities and strengthening the nation’s economy. Through its strong investment in workforce training initiatives, specialized practices and damage reduction, South32 continues to strengthen the future of society through a modern tailored mining industry.

South32’s Hermosa Project sets the bar high for new mining developments

Authored by: Carrie Smith

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