Mantoverde

Mantoverde is an open-pit copper-gold mine located in the province of Chañaral, Atacama Region, 56 kilometers southeast of the city of Chañaral and 100 kilometers north of the city of Copiapó, at an altitude of approximately 900 masl.

Mantoverde is located in close proximity to Capstone’s Santo Domingo project, as well as the recently acquired Sierra Norte deposit.

Operation

Mantoverde is a conventional open pit mining operation using truck-and-shovel technology. The mine currently operates a sulphide concentrator and a heap and dump run of mine (“ROM”) leaching and conventional SX-EW to produce copper in concentrate with gold as a by-product credit and high-purity LME Grade “A” copper cathodes. The mine consists of four pits situated along the Mantoverde fault, each of which contains both sulphide and oxide ores.

The mine owns a state-of-the-art desalination plant, located approximately 40 kilometers west of the mine that supplies all the water required by the operation.

Mantoverde operations commenced in 1995 with material treated through an SX-EW plant. In 2023, Capstone completed construction of the Mantoverde Development Project (“MVDP”). MVDP involved the addition of a sulphide concentrator (nominal 32,000 ore tonnes per day (“tpd”)) and tailings storage facility, and the expansion of the existing desalination plant and other minor infrastructure, in order to process sulphide ore. The final total project capital spend was $870 million, which was in line with the revised budget. After producing first copper concentrate in June 2024, the MVDP achieved commercial production in September 2024, and the mill ramped up to full nominal rates by year end.

The Copper Mark

The Copper Mark was awarded to our Mantoverde site in September 2023. The Copper Mark is the leading assurance framework for copper, created to demonstrate responsible production practices and the industry’s contribution to the United Nations Sustainable Development Goals. The Copper Mark uses a rigorous site-level assessment process to independently verify whether individual copper producing sites have responsible production practices using 33 criteria across three areas: Environmental, Social, and Governance.

Growth – MV Optimized and Mantoverde Phase II, and Cobalt

Capstone is currently progressing the next expansion of the sulphide concentrator. The Company has identified that the desalination plant capacity and major components of the comminution and flotation circuits of the Mantoverde Development Project are capable of sustaining average annual throughput of up to 45,000 tonnes per day with no major capital equipment upgrades. As per the 2024 Mantoverde Optimized (“MV Optimized”) Feasibility Study, this capital-efficient expansion extends throughput from 32,000 to 45,000 ore tonnes per day and extends the mine life from 19 to 25 years. The $176M project was sanctioned for development in Q3 2025 and is currently in the construction phase.

The Company is in the early stages of evaluating the next major phase of growth for Mantoverde, which could include the addition of an entire second processing line (“Mantoverde Phase II”). There are 0.2 billion tonnes of Measured & Indicated Mineral Resources adn 0.6 billion tonnes of Inferred sulphide Mineral Resources in addition to the reserves that are currently being considered as part of MV Optimized. In addition, exploration targets include the northern portion of the current Mantoverde pit and the northern extension (~10km long) of the projection of the prospective Atacama fault system, which are planned to assist in determining the lcoation of key infrastructure and the economic viability of the project.

The Company is also evaluating the potential to unlock cobalt production from the Mantoverde-Santo Domingo district. The cobalt recovery process comprises a pyrite flotation step to recover cobaltiferous pyrite from the tailings streams at Mantoverde and Santo Domingo and redirect it to the dynamic heap leach pads, which will be upgraded to a bioleach configuration through the addition of an aeration system as part of MV Optimized. The pyrite oxidizes in the leach pads and the solubilized cobalt is recovered via an ion exchange plant treating a bleed stream from the copper solvent extraction plant. The approach has been successfully demonstrated at the bench and pilot scales. An initial cobalt assay of expected quality has been sent to potential customers for feedback, which has been overall positive.

Geology and Exploration

The Mantoverde deposit is a typical iron oxide–copper–gold (IOCG) deposit located within the Atacama Fault System. It is located in an ancient mining district with numerous Fe, Fe-Cu-Au, Au and Mn deposits in the southern sector of the Atacama Fault System within the Cretaceous iron belt. Copper mineralization is oxidized down to approximately 200 m depth and two types of oxidized copper ores are recognized. The breccias in the sloping fault block contain abundant haematite with brochantite, minor antlerite, chrysocolla, malachite and atacamite, which occur in veinlets, patches and disseminated in the specularite matrix.

Mantoverde District and Near-Mine Exploration – Oxides and Sulphides

Mantoverde has a history of Mineral Reserves and Resources growth through successful exploration. The current Mineral Resource is open at depth in multiple locations along the main Mantoverde fault, and also north of the pit in the underexplored Animas and Santa Clara Corridor. Current exploration drilling programs are focusing on deeper high-grade zones and on sulphide and oxide areas in the northern portion of the deposit, which has potential to expand the current Mineral Resource and support conversion into Mineral Reserves.

Mantoverde also has significant potential to develop a larger mining district. Several oxide and sulphide opportunities exist within the mine’s 23 km land package along the Atacama Fault System. District targets identified to date include the Las Animas, Paloma, Las Juntas, San Manuel and La Reina, which are located between 4 and 8 km north of the current pit design. Recently Capstone completed pole-dipole ground geophysical survey together with a surface rock geochem and mapping program and is planning for an initial drill testing stage of those targets.

2025 Guidance

*Key Assumptions: CLP/USD: 900:1, Gold: $2,350/oz. Figures shown on a 100% basis. All figures in USD.

Virtual Tour

Use your mouse in the app window below for a virtual site tour of the Mantoverde Development Project.