Capstone Copper Reports Results of Phase 1 Drill Program at Mantoverde

Capstone Copper Corp. (“Capstone” or the “Company”) (TSX:CS) (ASX:CSC) is pleased to report initial exploration results from its Phase 1 drill program at Mantoverde in the Atacama region of Chile. Phase 1 included 30,000-metres of drilling focused on areas adjacent to the Mantoverde Optimized (“MV-O”) Pit Reserves, as well as priority targets located just north of the current operation. Assay results for the Phase 1 drill program have been received for approximately 24,700-metres of the 30,000-metre drill program.

Figure 1: Mantoverde Site Map, including location of current pits, Mantoverde Optimize Pit Reserves and Phase 1 drill locations

To view an interactive 3D presentation, please visit: https://vrify.com/decks/19778

Highlights are listed below, with corresponding images in Figures 1-5 and detailed results in Tables 1-2, including:

• Higher than expected grades in the Brecha Flores sector, where drill intercepts returned copper grades above those predicted by the current block model, including:
  • DDH25DS16: 176m of 0.77% copper from 654m, including 24m of 1.50% copper
  • DDH25DS28: 162m of 0.73% copper from 660m, including 18m of 1.07% copper
  • DDH25DS01: 144m of 0.65% copper from 528m, including 18m of 1.88% copper
• Results consistent with the current block model at Mantoverde Sur (“MVS”) and Mantoverde Norte (“MVN”), enhancing confidence and supporting the potential upgrade of the resource categorization, including:
  • DDH25DS24: 146m of 0.52% copper from 314m, including 34m of 1.07% copper
  • DDH25DS26: 274m of 0.39% copper from 318m, including 20m of 1.30% copper
  • DDH25DS09: 62m of 0.23% copper from 178m, including 64m of 0.62% copper
• Strong results along the Santa Clara Corridor confirming the presence of higher grades than the current block model with the potential for resource growth in between active pits, including:
  • DDH25DS08: step-out drilling returned 376m of 0.43% copper from 674m, including 64m of 0.98% copper
  • DDH25DS32: 100m of 0.43% copper from 656m, including 42m of 0.62% copper
  • DDH25DS27: 82m of 0.77% copper from 740m, including 30m of 1.04% copper
• Results from step-out drilling continue to demonstrate extension of the mineralization to the north of the current Mantoverde pit into the Animas area, confirming continuity along strike, including:
  • DDH25DS21: 102m of 0.41% copper from 96m, 26m of 0.46% copper from 248m, and 46m of 0.49% copper from 316m
  • DDH25DS25: 112m of 0.45% copper from 126m, including 28m of 0.67% copper
• District-scale exploration potential with the completion of a 10-kilometre Induced Polarization (IP) geophysical survey along the northern corridor, which has informed the location of high-priority targets that will be tested in Phase 2 of the drill program

Cashel Meagher, Capstone’s President and Chief Executive Officer, commented, “We are excited by the initial results from the Phase 1 drill program at Mantoverde, which we envision will improve our grade profile in the near-to-medium term highlighted by the results in the Brecha Flores sector. The results from step-out drilling at Animas and the Santa Clara Corridor are also very encouraging, highlighting the potential for future expansion projects such as Mantoverde Phase II. This early success supports our commitment to building a world-class, long-life copper district in the Tier 1 jurisdiction of Atacama, Chile. We look forward to advancing Phase 2 of the exploration program, which focuses on the highly prospective northern corridor of our Mantoverde concession and will continue to inform further opportunities for growth within our Mantoverde-Santo Domingo district.”

The Phase 1 drill program represents a portion of the ongoing two-year exploration program at Mantoverde, which is expected to total approximately $25 million and include 61,500-metres of drilling. There are currently up to seven drill rigs operating on site at Mantoverde.

Phase 1 consisted of 30,000-metres of drilling focused on areas adjacent to the Mantoverde Optimized Pit Reserves, including MVS, Brecha Flores, and MVN, aiming to improve copper grades and mineralization continuity within and near the pit boundaries. Phase 1 also included testing of priority targets located just north of the current Mantoverde pit at the Santa Clara Corridor and Animas. The initial results support the potential for resource growth and reserve conversion. Drilling has also intersected mineralization in areas assumed to be waste in the current life of mine plan and may have favourable implications on future stripping ratios. The results also confirm our understanding of the geological model and provide additional confidence in potential future expansion plans.

Phase 2 will include two main areas of focus and is expected to commence in Q4 2025. ~20,000 metres will be follow-up drilling at the targets adjacent to the northern portion of the pit, with the goal of improving grades and adding mineralization. The remaining ~11,500 metres of drilling will include testing of high-priority targets along the 10-kilometre-long northern corridor, which were defined based on the results of the induced polarization (“IP”) geophysical survey completed in Q1 2025.

Table 1 - DRILL RESULTS

1. Copper equivalent (“CuEq”) in the above table and this press release has been calculated using the following formula: Cu grade + [Au grade in g/t x (67.87% Au metallurgical recovery / 90.44% Cu metallurgical recovery) x ($2,600/oz Au price / 31.1035) / ($4.25/lb Cu price x 2204.623)] + [Co grade in ppm x (60% Co metallurgical recovery / 90.77% Cu metallurgical recovery) / ($15.00/lb Co price / $4.25/lb Cu price)]. Hole DDH25DS32 with “No data” for Co assumed a 0 value for Co.
2. Values over limits in Co (2,000 ppm).

Table 2 - DRILL HOLE LOCATION

MANTOVERDE OPERATION SUMMARY

Mantoverde (70%-owned by Capstone Copper and 30%-owned by Mitsubishi Materials Corporation) is an open-pit copper-gold mine located in the Atacama region of Chile. Since the 1990s, Mantoverde operated as an oxide mine producing copper cathodes from its 60,000 tonnes per annum capacity SX-EW plant. In 2023, Capstone Copper completed construction of the Mantoverde Development Project (“MVDP”) that enabled the mine to process its copper sulphide reserves, in addition to existing oxide reserves. The MVDP involved the addition of a sulphide concentrator and tailings storage facility, and the expansion of the existing desalination plant and other minor infrastructure. First saleable copper concentrate at MVDP was produced in June 2024 and commercial production was achieved in September 2024. In Q3 2025, Capstone Copper began development of the Mantoverde Optimized (“MV-O”) brownfield expansion, which is expected to increase total copper production at Mantoverde by approximately 20,000 tonnes per annum.

For further details, please see the press release dated October 1, 2024 announcing the results of the Mantoverde Optimized Feasibility Study and the updated Mineral Reserve and Resource estimate as at December 31, 2024 per the 2024 Annual Information Form.

QA/QC PROGAM

At Mantoverde, drill core is logged, photographed and cut in half with a hydraulic splitter at the Company’s on-site facilities. Half of the core is retained for reference, and the other half is sampled at regular 2.0-metre intervals. Sample preparation and analysis are performed by Geolaquim and GeoAssay, both certified independent laboratories. Copper, cobalt and other elements are determined by four-acid digestion with atomic absorption spectroscopy (AAS). Gold assays are performed by fire assay with atomic absorption spectroscopy (AAS). Drill samples from the Phase 1 drill program have been monitored through Capstone quality assurance and quality control (“QA/QC”) program, which follows internal operational procedures and industry best practices. The QA/QC program includes the routine insertion of certified standards (5%), coarse blanks (5%), fine blanks (5%), coarse duplicates (5%) and pulp duplicates (5%), yielding a blended QC insertion rate of approximately 25%.

QA/QC VALIDATION

The QA/QC validation process undertaken for the Phase 1 drill program of the Project is consistent with the process set out in the NI 43-101 technical report with respect to Mantoverde operation, titled “Mantoverde Mine, NI 43-101 Technical Report and Feasibility Study, Atacama Region, Chile”, dated November 14, 2024 with an effective date of July 1, 2024 and Capstone internal guidelines and best practices.

NOTE ON NI 43-101 COMPLIANT TECHNICAL REPORT

The conversion of drill results in this press release into NI 43-101 compliant mineral resources or mineral reserves required additional work and analysis that remains ongoing.

QUALIFIED PERSONS

Peter Amelunxen, P.Eng., Senior Vice President, Technical Services of Capstone Copper, a Qualified Person (“QP”), as defined by NI 43-101 reviewed and approved the content of this news release including the scientific and technical information.

About Capstone Copper Corp.

Capstone Copper Corp. is an Americas-focused copper mining company headquartered in Vancouver, Canada. Capstone’s operating portfolio of assets includes the Pinto Valley copper mine located in Arizona, USA, the Cozamin copper-silver mine located in Zacatecas, Mexico, the Mantos Blancos copper-silver mine located in the Antofagasta region, Chile, and the Mantoverde copper-gold mine, located in the Atacama region, Chile. Capstone’s growth pipeline includes the fully permitted Santo Domingo copper-iron-gold project, located approximately 35 kilometres northeast of Mantoverde in the Atacama region, Chile, as well as a portfolio of exploration properties in the Americas.

Capstone Copper’s strategy is to unlock transformational copper production growth while executing on cost and operational improvements through innovation, optimization and safe and responsible production throughout our portfolio of assets. We focus on profitability and disciplined capital allocation to surface stakeholder value. We are committed to creating a positive impact in the lives of our people and local communities, while delivering compelling returns to investors by responsibly producing copper to meet the world’s growing needs.

Further information is available at www.capstonecopper.com

Non-GAAP and Other Performance Measures

“Expansion capital” and “sustaining capital” are Alternative Performance Measures. Alternative performance measures are furnished to provide additional information. These non-GAAP performance measures are included in this presentation because these statistics are key performance measures that management uses to monitor performance, to assess how the Company is performing, to plan and to assess the overall effectiveness and efficiency of mining operations. These performance measures do not have a standard meaning within IFRS and, therefore, amounts presented may not be comparable to similar data presented by other mining companies. These performance measures should not be considered in isolation as a substitute for measures of performance in accordance with IFRS. For full information, please refer to the Company’s latest Management Discussion and Analysis published on its Financial Reporting webpage or on SEDAR+.