Del Toro Project

Overview

• Closed the acquisition of a 100% interest in the Del Toro mine from First Majestic Silver for up to US$60 million, in June 2026.
• Past-producing underground silver‑lead‑zinc mining complex in the Chalchihuites district, Zacatecas, with three mines and a 3,000 tpd processing facility
• Operated by First Majestic from 2013 to 2019 with significant historical production and established infrastructure
• Extensive exploration database including 631 drill holes totaling over 137,000 metres
• District-scale land package comprising 67 concessions covering ~2,095 hectares in a prolific mining region
• Fully permitted operation with access to power, water, roads, and experienced local workforce
• Significant exploration upside with multiple targets and mineralized zones open at depth and along strike

Geology and Mineralization

• The property hosts polymetallic silver‑lead‑zinc mineralization associated with carbonate replacement deposits (CRD), skarn, vein, and chimney systems
• Located within the Chalchihuites district of the Mesa Central province, near the Sierra Madre Occidental, a prolific metallogenic belt in Mexico
• Mineralization is hosted in Cretaceous limestone, shale, and skarn units, with intrusions of quartz monzonite–granodiorite controlling fluid flow and deposition
• Deposits occur as chimneys, mantos, breccias, and structurally controlled veins, with mineralized bodies extending over 300 m vertically and up to 750 m along strike
• Primary minerals include galena, sphalerite, pyrite, and silver sulphosalts, with oxidation products near surface
• Multiple mineralized zones across key mines (Perseverancia, San Juan, Dolores) with several areas open at depth and along strike

Extensive exploration database includes 631 drill holes totaling over 137,000 metres, supporting geological continuity and resource potential

Exploration Potential

• Post-acquisition (June 2026), Sierra Madre Gold and Silver gains a large historical exploration database and past-producing polymetallic district
• Del Toro hosts a magmatic-hydrothermal system with veins, chimneys, mantos, and skarn mineralization — historical work focused on veins, leaving carbonate replacement and skarn targets largely untested
• Geological mapping covers ~750 ha, plus 544 ha of drone surveys; multiple structural corridors and target areas defined
• 5,000+ soil, rock, and trench samples show strong Pb-Zn anomalies along the Carmen–Consuelo corridor and areas to the north-northeast; alteration mapping indicates high-temperature assemblages
• TITAN 24 DC/IP geophysical survey (~34.8 line-km) outlined 11+ anomalous zones with sulphide mineralization signatures
• Key target areas include Santa Teresa, Zaragoza, Cotorras, Carmen–Consuelo, Fanny–Lupita, and areas around the Perseverancia and San Juan mines
• 631 drill holes (~137,800 m) completed to date; many geophysical anomalies and favorable geology zones remain underexplored, with known zones open along strike and at depth
• District-scale opportunity with multiple untested targets and meaningful upside through systematic modern exploration

Historic Del Toro Mineral Resource Estimate (2020)

Notes for Historic Mineral Resource Estimates

Resources as disclosed in the Annual Information Form of First Majestic for the year ended December 31, 2024, dated March 31, 2025, available for review under First Majestic's SEDAR+ profile at www.sedarplus.ca. Notes for Historical Mineral Resource Estimates: Reported by First Majestic in a technical report titled "Technical Report for the Del Toro Silver Mine, Chalchihuites, and Zacatecas, Mexico" with an effective date of December 31, 2016 prepared by Ramon Mendoza Reyes, P.Eng., Jesus M. Velador Beltran, MMSA and Andrew Hamilton, P.Geo. and last updated in First Majestic's Annual Information Form with an effective date of December 31, 2020. The latest historical estimates were prepared by First Majestic internal "Qualified Persons" (as defined in NI 43-101) who have the appropriate relevant qualifications and experience in geology and resource estimation. The Mineral Resource estimates were prepared under the supervision of, or were reviewed by, David Rowe, CPG, Internal QP for First Majestic, a Qualified Person, as that term is defined in NI 43-101. Sample data was collected through a cutoff date of December 31, 2020. Metal prices considered for Mineral Resources estimates on December 31, 2020, were $22.50/oz Ag, $1,850/oz Au, $0.90/lb Pb and $1.05/lb Zn. Mineral Resource estimates have been classified in accordance with the CIM Definition Standards on Mineral Resources and Mineral Reserves, whose definitions are incorporated by reference into NI 43-101. In accordance with NI 43-101, the Del Toro Historical Mineral Resource Estimates use the terms "mineral resource", "measured mineral resource", "indicated mineral resource" and "inferred mineral resource", having the same meanings ascribed to those terms as in the CIM Standards. As these mineral resource estimates pre-date the Company's agreement to acquire Del Toro, the Company is treating them as "historical estimates" under NI 43-101, but they remain relevant as the most recent mineral resource estimates for Del Toro. No more recent estimates or data are available to Sierra Madre. Further drilling and resource modelling would be required to upgrade or verify these historical estimates as current Mineral Resources for the respective assets and accordingly, they should be relied upon only as a historical resource estimate of First Majestic, which pre-dates the Company's agreement to acquire Del Toro. Mr. Gregory Smith, P. Geo., a director of Sierra Madre, is a "Qualified Person" as defined by NI 43-101 and has reviewed and approved the technical data and information contained in this news release. However, a "Qualified Person" under NI 43-101 has not done sufficient work to classify the historical estimates as current Mineral Resources. Accordingly, a Qualified Person of the Company has not independently verified the Mineral Resources nor the other information contained herein, and the Company is not treating the historical estimates as current Mineral Resources. Although the Company is not treating this information as a current estimate, the Company believes David Rowe's work is reliable. Historical information may not be representative of expected results. Mineral Resources that are not mineral reserves do not have economic viability. Totals may not add up due to rounding.

Del Toro Mine

• Fully permitted past-producing underground Ag-Pb-Zn mine in the Chalchihuites district, Zacatecas, Mexico; previously operated by First Majestic Silver (2013–2019), currently on care and maintenance
• Three primary underground mining centres: Dolores, Perseverancia, and San Juan
• On-site flotation plant (~2,000–3,000 tpd capacity) producing Ag-Pb and Ag-Zn concentrates during operation
• Extensive existing infrastructure: underground mine development, flotation plant, tailings facilities (including new permitted area), power, water, and all-weather road access
• Historical mineral resources exist but are not NI 43-101 compliant — require data validation, re-assaying, and additional drilling before conversion

Dolores

• Hosts the Dolores, Purisima, and Santa Teresa (Alto & Bajo) vein systems; Ag-Pb-Zn mineralization in veins associated with intrusives and carbonate units
• ~57 m average drill spacing; mineralization open along strike and at depth

Perseverancia

• Chimney and replacement mineralization in altered limestone and shale; principal zones include San Nicolas and Escondida veins
• High-grade Ag with significant Pb-Zn; mineralized bodies extend vertically hundreds of metres with depth extension potential
• ~60 m average drill spacing

San Juan

• Largest and most complex centre; hosts vein-stockwork, breccia pipes, chimneys, and CRD zones
• Key zones: Lupita, San Jose, and Cuerpo 3 (most developed); Ag-Pb-Zn with minor Au
• Drill spacing ranges from ~25 m (Cuerpo 3) to ~50 m (Lupita, San Jose); deeper and peripheral zones remain open and underexplored

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