Guanajuato Silver's April 2026 updated resource and reserve report on the Bolañitos project in Guanajuato State, Mexico, records 1,068,000 oz of silver and 39,939 oz of gold produced in 2024 and 2025.
The NI 43-101 Technical Report: Updated Mineral Resource and Reserve Estimates for the Bolañitos Project, Guanajuato State, Mexico, was prepared by Hard Rock Consulting for Guanajuato Silver Company, Ltd. with an effective date of March 19, 2026 and a report date of April 23, 2026. The Bolañitos plant was commissioned in 2006. A second ball mill and flotation circuit added in 2011 raised capacity to 1,200 t/d, and 2012 additions of a screen, flotation and cleaner cells and conveyors raised it to 1,600 t/d. The mill now treats ore from the Bolañitos and San Ignacio mines at close to 1,100 t/d.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | March 19, 2026 | Not applicable | Hard Rock Consulting for Guanajuato Silver Company, Ltd. |
| Installed capacity | 1,600 | t/d | Since 2012 expansion |
| Throughput, 2024 to 2025 average | 1,124 | t/d | Not applicable |
| Head grade, 2024 to 2025 average | 47.9 g/t Ag, 1.69 g/t Au | Not applicable | Not applicable |
| Production, 2024 and 2025 | 1,068,000 oz Ag, 39,939 oz Au | Not applicable | Not applicable |
| Silver recovery | 84.4 average (monthly 80 to 95) | % | Not applicable |
| Gold recovery | 89.5 average (monthly 85.8 to 92.5) | % | Not applicable |
| Crushed product | 85 to 90% passing 9.5 mm | Not applicable | Three-stage crushing |
| Ball mills | 9.5 x 14 ft (450 kW) and 11 x 18.6 ft (750 kW) | Not applicable | Cyclone overflow P80 74 µm |
| Concentrate target | 3 to 4 kg/t Ag, below 1.0% As | Not applicable | Column cell not used since 2020 |
| Concentrate moisture | 13 to 17 | % | Filter press; shipped in 35 t trucks |
Overview
Ore from the two mines is campaigned so that the metallurgical balances stay separate. Because an ore switch takes about six hours, all San Ignacio ore, about 10% of feed, is treated in one campaign each month, and Bolañitos ore fills the rest of the month. In 2024 and 2025 the mill averaged 1,124 t/d at 47.9 g/t silver and 1.69 g/t gold, producing 1,068,000 oz of silver and 39,939 oz of gold over the two years.
Key Process Stages
Crushing. Haul trucks of 10 and 20 t deliver ore to a patio, and a front-end loader feeds a grizzly with 35.5 cm openings, with a hydraulic hammer for oversize. A 61 by 91 cm (24 by 36 inch) jaw crusher feeds two coarse ore bins. A 6 by 14 ft screen with 9.5 mm openings sends oversize to a 4.25 ft standard-head Symons cone crusher. A second 5 by 10 ft screen sends its oversize to a Metso HP200 tertiary cone crusher. Product at 85 to 90% passing 9.5 mm is stored in fine ore bins of 250 t and 350 t.
Grinding. Two ball mills are fed independently from their own bins: No. 1 is 9.5 by 14 ft with a 450 kW (600 hp) motor, and No. 2 is 11 by 18.6 ft with a 750 kW (1,000 hp) motor. Each has its own cyclone cluster, and both produce flotation feed at P80 74 µm.
Flotation. The Ball Mill No. 1 circuit has four 500 ft³ cells: two roughers that send high-grade concentrate straight to the cleaners, and two scavengers whose concentrate returns to the roughers. The Ball Mill No. 2 circuit has nine 300 ft³ cells fed with cyclone overflow and cleaner tails. Its first two rougher concentrates go directly to dewatering, and its other rougher and scavenger concentrates feed the cleaners. Six 100 ft³ primary cleaner cells take concentrate from both circuits. Reagents are Aerophine 3416 collector, Aerophine 7310 promoter, Orion A99 activator and promoter, and PQM CC-1065 frother.
Concentrate handling. Final concentrate is thickened to 60% solids and filter pressed to 13 to 17% moisture, then shipped in 35 t trucks to concentrate traders.
Additional Interesting Data and Summary
A column cell for second-stage cleaning was installed in 2012 and discontinued in December 2013. It reached the target silver grade of 7 to 9 kg/t but also concentrated arsenic, which drew heavy penalty charges from concentrate refiners. It has not been used since 2020, and the target concentrate is now 3 to 4 kg/t silver with arsenic below 1.0%. Guanajuato Silver is building a tailings thickener to improve water management and tailings deposition. The report states no major changes to the mill or flowsheet are planned.
In summary, Bolañitos is a long-running two-line flotation mill working below its 1,600 t/d capacity, campaigning two ores, and trading concentrate grade for lower arsenic, at recoveries of about 89.5% for gold and 84.4% for silver.
Key Processes
- Jaw crushing and two-stage cone crushing to 9.5 mm
- Two independent ball mill and cyclone circuits to P80 74 µm
- Rougher and scavenger flotation in two lines
- Primary cleaner flotation
- Concentrate thickening and filter pressing
- Campaign processing of two ore sources
Source: NI 43-101 Technical Report: Updated Mineral Resource and Reserve Estimates for the Bolañitos Project, Guanajuato State, Mexico, prepared by Hard Rock Consulting for Guanajuato Silver Company, Ltd., effective date March 19, 2026.
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Bolañitos Project — 2021 Technical Report (Recovery Methods)
Bolañitos Project — 2021 Technical Report (Recovery Methods)
| Company | Endeavour Silver Corp. |
| Date | 2021 |
| Region | Guanajuato, Mexico |
| Commodities | Silver, Gold |
Executive Summary
The 2021 production data for the Bolañitos plant indicates a throughput of 418,514 tonnes of ore, grading 42 g/t silver and 2.02 g/t gold. Recoveries averaged 87% for silver and 90.7% for gold, resulting in 483,507 oz of silver and 24,730 oz of gold recovered. The plant operated at an average throughput of 1,163 tonnes per operating day, slightly exceeding the planned rate of 1,100 t/d, with only 4 days of maintenance downtime recorded.
The processing circuit has undergone upgrades since 2012, including the addition of a vibration screen and additional flotation cells. The current layout involves run-of-mine ore being crushed through a primary jaw crusher, secondary and tertiary cone crushers, and then ground in two ball mills. The ground pulp is processed through a flotation circuit consisting of rougher, scavenger, and cleaner cells, with the column flotation cell discontinued in 2020 due to arsenic recovery issues.
Final concentrate is dewatered using a thickener and filter press to 13-17% moisture before shipment. Target concentrate grades are maintained between 3 to 4 kg/t silver while keeping arsenic grades below 1.0%. The plant infrastructure supports the continuous operation of the Bolañitos project, demonstrating stable recovery performance in 2021 compared to previous years.
Processing Details
Website: https://edrsilver.com/portfolio/reserves-resources/reserves-resources/
Report Date: 2021
Region: Guanajuato, Mexico
Commodity: Silver, Gold
Bolañitos Project — 2020 Technical Report
Bolañitos Project — 2020 Technical Report
| Company | Endeavour Silver Corp. |
| Date | 2020 |
| Region | Mexico |
| Commodities | Silver, Gold |
| Status | Operating |
Executive Summary
The 2020 Technical Report details the operational performance of the Bolañitos plant, which processed 331,175 tonnes of ore grading 40 g/t silver and 2.02 g/t gold. The plant achieved recoveries of 84.8% for silver and 89.5% for gold, resulting in the production of 358,181 oz of silver and 19,249 oz of gold. These recoveries represented improvements of 5% for silver and 8% for gold compared to previous operations at higher throughput rates.
The processing plant is designed for a planned rate of 1,100 tonnes per day, with an average throughput of 1,078 tonnes per day recorded in 2020. This managed throughput rate was implemented to maximize recoveries, moving away from the previous operation of 1,600 tonnes per day. The facility includes significant infrastructure upgrades from 2012, including vibration screens, additional flotation cells, and a flocculent mixing system.
The recovery circuit begins with run-of-mine ore hauled by dump trucks and loaded onto a grizzly. The ore undergoes primary crushing via a jaw crusher, followed by secondary and tertiary cone crushing. The ground ore is then processed through a grinding circuit consisting of two ball mills before entering the flotation circuit. The final concentrate is thickened and filtered before shipment to traders.
Processing Profile
Website: https://edrsilver.com/news-media/news/endeavour-silver-completes-sale-of-bolanitos-mine-13329/
Report Date: 2020
Region: Mexico
Project Status: Operating
Commodity: Silver, Gold
Throughput:
Mine Life:
Mine Type:
Ore type:
Consolidated report summaries
The following former standalone pages about this operation were consolidated here on October 25, 2026. They are retained for source traceability; dates and figures reflect each report’s own effective date and may be superseded by the current information above.
Bolañitos Plant — 2011 Technical Report
This profile describes the Bolañitos flotation plant as it operated in 2011, based on the December 31, 2011 effective-date Technical Report for the Guanajuato Mines Project. The plant processed ore from the Cebada and Bolañitos-Lucero mines on a campaign basis, producing a single concentrate trucked to Guanaceví for doré production.
Report context
The Bolañitos plant is one of two processing facilities described in the 2011 Technical Report for Endeavour Silver Corp.’s Guanajuato Mines Project, Guanajuato State, Mexico. The report was signed March 30, 2012 with an effective date of December 31, 2011. The processing description draws on Sections 13.0 (Mineral Processing and Metallurgical Testing) and 17.0 (Recovery Methods) of that report. All data show 2011 operating performance and 2011 metallurgical testing. The plant is not a stand-alone doré producer; its concentrate is shipped to the Guanaceví plant for final smelting.
Processing route
Ore receiving and crushing
Run-of-mine ore from the Cebada and Bolañitos-Lucero mines arrives at the plant in the size range of 250 to 375 mm. A primary jaw crusher receives the ore, after which two ore bins, each with a 450 t capacity, allow different ore types to be crushed and stored independently. This bin arrangement optimises plant availability and reduces change-over time when switching between ore sources.
Secondary cone crushing reduces ore to 50 mm, followed by tertiary crushing to 9–10 mm. After tertiary crushing, a second set of two ore bins, each with a 120 t capacity, provides additional plant flexibility. A conveyor belt beneath the tertiary crusher bins is fitted with a weightometer that is regularly checked and re-calibrated by plant operators. Manual samples are taken at this point to determine the plant head grade.
Grinding and flotation
Two ball mills grind the crushed material to 65% passing 74 microns. The grinding product is then subjected to conventional flotation in both column and tank cells. Automatic samplers collect samples of tailings and concentrate. A single concentrate is produced, grading approximately 11.61 kg/t silver and 169 g/t gold.
Dewatering and product dispatch
The flotation concentrate is dewatered in a conventional thickener, followed by filtration and drying in a warm air drier (gas drier). At the maximum processing rate of 1,200 t/d, the plant produces between 5 and 13 t/d of concentrate. The dried concentrate is stored and sampled for grade and moisture content before being trucked to Endeavour Silver’s Guanaceví plant, where it is added to the mill stream for doré production. The Bolañitos plant does not produce doré directly.
Tailings and water management
Tailings are sampled automatically from the pulp sent to the tailings facility. The report does not provide details on tailings disposal method, water recovery circuits, or reagent addition systems. Reagent dosages are varied per ore type during campaign milling, but specific reagent types and consumption rates are not given for the production circuit.
Metallurgical balance and sampling
Key points in the process circuit are sampled to generate a monthly metallurgical balance and for quality control:
- Head grade from the conveyor feeding the milling circuit
- Wet head grade from the pulp feeding the flotation circuit
- Concentrate grade from the pulp of the final product going to thickening
- Tails grade from the pulp sent to the tailings facility
Samples are prepared and analyzed at the Bolañitos mine laboratory, which produces a daily report containing gold and silver grades for each of three 8-hour shifts. The laboratory also measures sample moisture content for dry tonnage calculations. A metallurgical balance for the concentrates is generated each shift using gold grade, silver grade, percent moisture, and tonnage from the weightometer on the grinding circuit feed belt. After filtering and drying, concentrate samples are taken for grade and moisture content, and the daily calculated balance is checked against the mass of concentrate produced. The daily balance forms the basis of the monthly reconciliation report, which is reviewed by senior staff and cross-checked against the mass and grade of dried concentrate samples.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Plant throughput (2011) | 238,797 t | Actual annual production |
| Feed grade – silver | 183 g/t | Actual annual average |
| Feed grade – gold | 2.51 g/t | Actual annual average |
| Silver recovery | 84.9% | Actual annual average |
| Gold recovery | 86.2% | Actual annual average |
| Gold production | 16,608 oz | Actual annual total |
| Silver production | 1,192,335 oz | Actual annual total |
| Concentrate grade – silver | ~11.61 kg/t | Reported typical |
| Concentrate grade – gold | ~169 g/t | Reported typical |
| Concentrate production rate | 5–13 t/d | At 1,200 t/d processing rate |
| Maximum processing rate | 1,200 t/d | Design capacity |
| Grind size | 65% passing 74 microns | Operating target |
| Primary crusher feed size | 250–375 mm | Operating range |
| Secondary crusher product | 50 mm | Operating target |
| Tertiary crusher product | 9–10 mm | Operating target |
| Ore bin capacity (primary) | 2 × 450 t | Design |
| Ore bin capacity (secondary) | 2 × 120 t | Design |
Project website: https://www.mining.com/endeavour-silver-sells-bolanitos-mine-to-guanajuato-in-50m-deal/
Metallurgical testwork results (2011)
| Parameter | Value | Basis |
|---|---|---|
| Cebada concentrate – Ag extraction (24 hr, bottle roll) | 87% average | Testwork result |
| Cebada concentrate – Au extraction (24 hr, bottle roll) | 55% average | Testwork result |
| Cebada concentrate – Au extraction (CIL) | ~80% | Testwork result |
| Bolañitos concentrate – Ag extraction | 73% average | Testwork result |
| Bolañitos concentrate – Au extraction | 93% average | Testwork result |
| Blend composite – Ag extraction (72 hr, bottle roll) | 90–98% range | Testwork result |
| Blend composite – Au extraction (72 hr, bottle roll) | 83–96% range | Testwork result |
| Lime consumption (blend composite) | ~0.5 kg/t | Testwork average |
| Sodium cyanide consumption (blend composite) | ~32 kg/t | Testwork average |
Technical qualifications
The processing descriptions in Sections 13.0 and 17.0 of the Technical Report are based on 2011 operating data and 2011 metallurgical testing. The report explicitly states that metallurgical testwork results for improved extractions were not easily duplicated and that several leaching variables required optimisation. Endeavour Silver planned continued testing in 2012 at both the Guanaceví and G&T Metallurgical laboratories. The concentrate is trucked to Guanaceví for doré production, not smelted at Bolañitos. The flowsheet (Figure 17.1) is supplied by Endeavour Silver and dated January 2012. All recovery figures are actual 2011 operating averages, not design targets or testwork projections. The report does not describe tailings dam specifications, water balances, reagent consumption in the production circuit, or equipment sizing details. No resource or reserve figures are included in this profile.
Source: Endeavour Silver Corp., Technical Report on the Resource and Reserve Estimates for the Guanajuato Mines Project, Guanajuato State, Mexico, Effective Date December 31, 2011, Signing Date March 30, 2012. Sections 13.0 (Mineral Processing and Metallurgical Testing) and 17.0 (Recovery Methods). No original page numbers cited.
