Name of the Mine
Terronera mine.

Location  
Near Santiago de los Pinos, within the municipality of San Sebastián del Oeste, in Jalisco state, Mexico.

Mine Owner/s  
Midtier precious metals mining company Endeavour Silver Corporation (EDR).

Brief Description  
Terronera is set to become EDR’s flagship operation.

The underground mine consists of the Terronera and La Luz deposits, which feed a centralised processing plant.

Developed with mechanised underground ramp access, the mine has an expected ten-year mine life.

Brief History  
EDR acquired the Terronera property in 2010 to build a high-grade, silver/gold underground mining operation.

After more than a decade of planning, including exploratory drilling, technical reports, environmental assessments and the evaluation of multiple operating scenarios, construction started in 2023 and was completed in the first quarter of 2025. The operation achieved commercial production in October 2025.

Primary Metals/Minerals  
Silver and gold.

Secondary Metals/Minerals  
None stated.

Geology/Mineralisation  
The San Sebastián del Oeste mining district is situated at the southern end of the Sierra Madre Occidental metallogenic province, a major north-northwest-trending volcanic belt formed mainly during the Tertiary period. This belt is more than 1 200 km long, and 200 km to 300 km wide, and contains most of Mexico’s gold and silver deposits. It is also recognised as one of the largest epithermal precious-metal systems in the world.

Within this district, mineralisation occurs as high-grade silver-gold epithermal veins. These are low-sulphidation deposits with typical adularia-sericite alteration, which is the standard alteration style seen in many Mexican epithermal vein systems. The veins are mainly hosted in volcanic rocks, including lava flows and fragmental volcanic units, and in some areas they also occur within shale-rich sedimentary rocks and their metamorphosed equivalents.

The Terronera project is located in the geologically complex Jalisco Block, at the western end of the younger Trans-Mexican Volcanic Belt, which developed from the early Miocene to late Pliocene. In the San Sebastián del Oeste district, the most important mineralised veins are controlled by west-northwest- to north-west-striking structures linked to a strike-slip fault system.

At Terronera, the host geology comprises a volcano-sedimentary sequence consisting of shale, sandstone and narrow calcareous-clayey layers, overlain by tuffs, volcanic breccias and mainly andesitic lava flows. These units are exposed mostly in the north-central part of the district, while granitic to granodioritic intrusive rocks occur farther north.

Drilling has traced the main Terronera vein for about 1.5 km along strike, from surface to a maximum drilled depth of 546 m, with an average true width of 3.9 m. Additional hanging-wall and footwall veins are also present. Overall, mineralisation is hosted mainly in volcanic flow rocks, pyroclastic and epiclastic units, associated shale horizons and their metamorphic equivalents.

Reserves  
The mine had total probable reserves of 7.38-million tonnes grading 197 g/t silver and 2.18 g/t gold, equating to 374 g/t of silver equivalent as at December 31, 2024.

Resources  
Total inferred resources as at December 31, 2024, were estimated at 997 000 t grading 509 g/t silver and 0.95 g/t gold, equating to 590 g/t silver equivalent.

Total inferred resources for the La Luz deposit as at December 31, 2024, were estimated 61 000 t grading 150 g/t silver and 11.35 g/t gold, equating to 1 000 g/t of silver equivalent.
 
Type of Mine
Underground.

Mining Method  
Sublevel stoping in the form of longhole drill-and-blast, with backfill.

Major Infrastructure/Equipment  
Terronera has extensive on site infrastructure and services to support the mining operation, which includes a 2 000 t/d flotation plant, three mine portals, a truck shop and a wash bay; a maintenance workshop and a warehouse; road and helipad access routes; on-site power generation and distribution; wash and tailings storage facilities; sewage and potable water treatment facilities; employee accommodations and a dining hall; an administration building and a laboratory; mine emergency services; and a plant nursery.

Prospects  
Operations are scheduled to shift into higher-grade areas by the second half of 2026, which is expected to significantly improve grade averages. 

Contact Details 
Endeavour Silver 
Tel +1 604 685 9775
Email info@edrsilver.com
Website https://edrsilver.com/