Guanajuato Silver's 2025 report for the El Cubo and El Pingüico silver-gold complex in Guanajuato, Mexico, recorded 81.3% silver and 86.9% gold recovery from January to July 2024. It identifies changes that could raise plant capacity to 1,584 t/d.
The NI 43-101 Technical Report on the El Cubo and El Pingüico Silver Gold Complex, Guanajuato, Mexico, was prepared by APEX Geoscience for Guanajuato Silver Company Ltd. (GSilver), with an effective date of August 1, 2024 and a signing date of January 16, 2025. The El Cubo plant was built in 2013 and run by Endeavour Silver until 2019, at 1,500 to 2,000 t/d in 2017 and 2018. GSilver refurbished it and modified the secondary crushing area and the grinding discharge grates, and it now runs at 1,350 t/d. Capacity could rise to 1,584 t/d by reconfiguring crushing, installing larger pumps in grinding, clarification and filtration, and adjusting the tailings dam. A gravity circuit was recently added to recover native silver, gold and electrum.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | August 1, 2024 | Not applicable | APEX Geoscience for Guanajuato Silver Company Ltd. |
| Current capacity | 1,350 t/d | Not applicable | Potential 1,584 t/d |
| Feed storage | Up to 3,000 t | Not applicable | El Cubo underground and El Pingüico stockpiles |
| Primary crusher | Jaw (150 hp), 40 t/h | Not applicable | Fed by front-end loader over a grizzly |
| Secondary crushing | Screen and cone crusher | Not applicable | Minus 5/8 inch product |
| Mill feed bin | 650 t | Not applicable | Slot feeder at 37.5 t/h |
| Ball mill | 12 ft x 14 ft EGL, single stage | Not applicable | Closed with cyclones to 75 µm (200 mesh) |
| Gravity | Falcon concentrator | Not applicable | Native silver, gold and electrum |
| Flotation | Five 30 m³ rougher cells, two Denver cleaner stages | Not applicable | 50 ft³ cleaner cells |
| Concentrate | 8 m thickener, Diemme filter press | Not applicable | About 12 t/d shipped |
| Tailings | 21 m Outotec thickener to about 60% solids | Not applicable | Filtered and dry stacked |
| Recovery (Jan to Jul 2024) | Ag 81.3, Au 86.9 | % | 48.05 g/t Ag, 0.92 g/t Au head |
| Power | 6.5 MW contracted | Not applicable | About 1,420,000 kWh a month |
Overview
Mill feed from El Cubo underground and other sources is reclaimed by front-end loader to a primary jaw crusher. It is conveyed to a rail car dump hopper, then screened and crushed in a secondary cone crusher to minus 5/8 inch. A single-stage ball mill closed with hydrocyclones grinds to 75 µm, and a Falcon gravity circuit recovers coarse precious metals. The slurry is conditioned and floated in a rougher bank and two cleaner stages. The concentrate is thickened, filter pressed and trucked to a refinery. Rougher tails are thickened, filtered and dry stacked.
Key Process Stages
Crushing. The crusher discharges into the rail car dump hopper at a single point, which limits storage when only the primary crusher runs. Clamshell feeders deliver the crushed ore to a vibrating screen. Screen oversize goes to the cone crusher, and the combined product goes to the 650 t mill feed bin. The crushing and screening circuits run at about 100 t/h until the bin is full and then stop.
Grinding and gravity. The ball mill is 12 by 14 ft, and the plant also lists 9 by 9 ft and 9 by 10 ft ball mills. The report describes the Falcon gravity circuit as treating the hydrocyclone stream and returning its tails to the mills.
Flotation. Cyclone overflow is conditioned with reagents and fed to five 30 m³ tank cells. Rougher concentrate is cleaned in four first cleaner cells and two second cleaner cells, all 50 ft³ Denver cells.
Concentrate handling. Concentrate is thickened in an 8 m high-rate thickener to about 55% solids. It is dewatered in a 1.5 m by 1.5 m Diemme plate-and-frame press holding 6 to 8 t per cycle. The filtered concentrate drops to the floor and is loaded into trucks by front-end loader.
Tailings. Rougher tails go to a 21 m high-rate Outotec thickener at about 60% solids and are then filtered for a dry stack tailings facility. Process water comes from underground workings and recycled water from the tailings basins.
Additional Interesting Data and Summary
From October 2021 to the effective date, the plant processed 862,979 dry tonnes from the complex, producing 1,437,248 oz of silver and 21,008 oz of gold. The plant is at about 2,200 m elevation, which was taken into account in sizing equipment and motors.
In summary, the 2025 El Cubo report describes a refurbished 1,350 t/d silver-gold plant. Two-stage crushing, ball milling, gravity and flotation produce a single precious metal concentrate, and tailings are filtered and dry stacked.
Key Processes
- Jaw and cone crushing to minus 5/8 inch
- Single-stage ball milling to 75 µm
- Falcon gravity concentration
- Rougher and two-stage cleaner flotation
- Concentrate thickening and filter pressing
- Tailings thickening, filtration and dry stacking
Source: NI 43-101 Technical Report on the El Cubo and El Pingüico Silver Gold Complex, Guanajuato, Mexico, prepared by APEX Geoscience Ltd. for Guanajuato Silver Company Ltd., effective date August 1, 2024.
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.
Preliminary Economic Assessment – El Cubo
This Preliminary Economic Assessment describes the processing plan for the El Cubo project, which will use the existing El Cubo Mill at a design rate of 750 tonnes per day to produce gold-silver concentrate from underground mine feed and surface stockpiles.
The El Cubo Mill was constructed as a conventional crushing, grinding, and flotation plant. It includes two-stage crushing, ball mill grinding, reagent storage, flotation, flotation concentrate filtration for product shipment, and tailings disposal. The plant will treat precious metals bearing ore using conventional methods. The mill will be operated at 750 tonnes per day to produce approximately 12 tonnes of gold-silver concentrate. That rate will be achieved by a combination of feed from the El Cubo underground mine and the El Pinguico above-ground and underground stockpiles.
Historical recoveries from the El Cubo Mine for ore processed through this mill averaged 87% for silver and 86.5% for gold. However, a 1,000-tonne bulk sample taken from the stockpile located above ground at the El Pinguico shaft and processed through a neighboring mill of approximately the same configuration averaged 60% for silver and 75% for gold. These results suggest a notable difference in recovery between the two feed sources.
Water supply for the El Cubo Mill will be from the existing underground workings, which currently make sufficient water for the plant requirements. Power supply will be from an existing 13 kV overhead transmission line. The El Cubo site is located at an elevation of approximately 2,200 meters above sea level, which was considered in equipment and motor design.
The plant design is based on a throughput rate of 750 tonnes per day or 34 tonnes per hour. Considering mine availability and plant maintenance downtime, the annual rate is estimated to be 273,750 tonnes per year. Mining rates have tentatively been set at 250 tonnes per day for initial operation and would ramp up to 750 tonnes per day during the first year of operation.
The El Cubo Mill has a minimum rate that it must be operated at to keep tanks and lines clear and operational. The crushing circuit is designed to process 100 tonnes per hour, which requires that the plant only be operated approximately 8 hours per day to provide the required tonnage to fill the ball mill feed bin for several days of operation. Likewise, the plant would only need to operate approximately 8 hours per day at 30 tonnes per hour to process the initial feed rate of 250 tonnes per day. Hence, the plant would likely campaign ore through the crushing and milling circuit once sufficient ore has been stockpiled by the mine.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Plant throughput rate | 750 | tonnes per day | Design rate |
| Plant throughput rate | 34 | tonnes per hour | Design rate |
| Annual throughput | 273,750 | tonnes per year | Considering mine availability and maintenance downtime |
| Concentrate production | 12 | tonnes per day | Gold-silver concentrate |
| Initial mining rate | 250 | tonnes per day | Tentatively set for initial operation |
| Crushing circuit rate | 100 | tonnes per hour | Design rate |
| Ball mill feed rate | 37.5 | tonnes per hour | Regulates single stage ball mill |
| Bond Work Index | 16-21 | kWh/t | |
| Ball Mill Feed (F80) | 16,000 | microns | |
| Product Size (P80) | 74 | microns | 200 mesh |
| Historical silver recovery | 87 | % | El Cubo Mine average |
| Historical gold recovery | 86.5 | % | El Cubo Mine average |
| Bulk sample silver recovery | 60 | % | El Pinguico stockpile sample |
| Bulk sample gold recovery | 75 | % | El Pinguico stockpile sample |
| Water supply | Not stated | Not applicable | Existing underground workings |
| Power supply | 13 | kV | Existing overhead transmission line |
| Elevation | 2,200 | meters | Above sea level |
| Product size | 14,000 | microns | Primary crusher product |
Overview
The El Cubo project involves reactivation of the existing El Cubo Mill to process ore from the El Cubo underground mine and stockpiles at El Pinguico. The processing facility uses conventional crushing, grinding, and flotation technology to produce a gold-silver concentrate. The operation is designed around a 750 tonne per day throughput rate, with initial operation at a lower rate expected during ramp-up.
Key Process Stages
The processing flowsheet consists of several integrated stages. Rail cars from the El Cubo underground mine discharge primary crushed ore into a 650-tonne rail dump storage hopper at a rate of 30 tonnes in 10 minutes. The rail cars may discharge along the entire length of the rail dump storage hopper. Trucks haul ore from El Pinguico and place material in a storage area that can contain up to 3,000 tonnes. Ore trucks from El Cubo will also place material in the same storage area.
Primary crushed ore is discharged from the rail dump hopper via a series of clam shell feeders onto a series of belts that carry the material to a vibrating screen. The crushing circuit processes ore at approximately 40 tonnes per hour for the primary crusher. Crusher product falls onto a conveyor that transports the material to the rail car dump hopper. This configuration limits the storage bin storage capacity if only the primary crusher is operated as a source of crushed ore feed.
Secondary crusher product is discharged onto the vibrating screen product conveyor and the combined stream is conveyed to a 650-tonne mill storage feed bin. The minus 5/8-inch material is reclaimed from the 650-tonne mill storage feed bin with a slot feeder and fed to a single stage ball mill at the rate of 37.5 tonnes per hour. The 12 foot diameter by 14 foot EGL ball mill operates in closed circuit with hydro-cyclones and grinds the material to a 200 mesh (75 micron) product size.
Cyclone overflow flows by gravity to a conditioning tank where flotation reagents are added. Conditioned slurry is fed to a 5-stage 30 cubic meter tank cell rougher flotation circuit. Flotation concentrate is filtered for product shipment. Tailings are thickened to approximately 55% solids and pumped to a conventional tailing pond for final disposal.
Additional Interesting Data and Summary
The El Cubo Mill was recently operated at 1,500 tonnes per day of ore to produce approximately 25 tonnes of gold-silver concentrate. Due to restrictions in the mine, mill feed was curtailed to approximately 700 tonnes per day at the end of 2019. This historical operating data provides context for the current design rate of 750 tonnes per day.
The crushing circuit is designed to process 100 tonnes per hour, which requires that the plant only be operated approximately 8 hours per day to provide the required tonnage to fill the ball mill feed bin for several days of operation. The intermittent nature of the crushing operation means that plant operators will need to campaign ore through the circuit once sufficient ore has been stockpiled.
The design parameters include a Bond Work Index range of 16-21 kWh/t, a ball mill feed size of 16,000 microns, and a product size of 74 microns. The primary crusher has a product size of 14,000 microns. These process design criteria show the ore characteristics expected from the combined feed sources.
Key Processes
- Two-stage crushing with vibrating screen
- Single-stage ball mill grinding in closed circuit with hydro-cyclones
- Reagent addition in conditioning tank
- 5-stage tank cell rougher flotation circuit
- Concentrate filtration for product shipment
- Tailings thickening to approximately 55% solids and disposal to conventional tailing pond
- Ore reclaim from 650-tonne mill storage feed bin with slot feeder
Source: Preliminary Economic Assessment – El Cubo, 2021.
Project website: Preliminary Economic Assessment – El Cubo
El Cubo/El Pingüico Silver Gold Complex — 2024 Technical Report
The El Cubo processing plant, constructed in 2013, applies a two-stage crushing, ball mill grinding, gravity, and flotation flowsheet to treat feed from the El Cubo/El Pingüico Silver Gold Complex.
Report context
This technical report is dated August 1, 2024. The mineralized material produced from El Cubo and from surface stockpiles at El Pingüico is processed at the El Cubo processing plant, located within the El Cubo/El Pingüico Silver Gold Complex. The plant was constructed in 2013 and operated by Endeavour Silver from 2013 to 2019.
Processing route
Plant capacity and historical operations
Historical operating records from 2017 to 2018 indicate a processing rate of 1,500 to 2,000 tonnes per day during that period. Since refurbishment of the plant by GSilver and modifications to the secondary crushing area and grinding discharge crates, the plant operates at a capacity of 1,350 tonnes per day. The report states there is potential to increase capacity to 1,584 tonnes per day by reconfiguring the crushing area, installing pumping equipment with higher capacity in the grinding, clarification, and filtration areas, and making tailings dam adjustments.
Crushing and grinding
Feed material from the El Cubo underground operations and mineralized material from other sources is placed in a storage area with capacity of up to 3,000 tonnes. Mill feed is reclaimed using a front-end loader and fed to a primary crusher grizzly, which feeds a primary crusher at 40 tonnes per hour. Crusher product moves by conveyor to a rail car dump hopper, discharging at a single point. Material is withdrawn via clam shell feeders onto belts to a vibrating screen. Screen oversize goes to a secondary cone crusher; screen undersize at minus 5/8-inch joins secondary crusher product on a conveyor to a 650-tonne mill feed storage bin.
Minus 5/8-inch material is fed from the storage bin by slot feeder to a single-stage ball mill at 37.5 tonnes per hour. The 12-foot diameter by 14-foot EGL ball mill operates in closed circuit with hydro-cyclones, grinding to a 200 mesh (75 μm) product size. Cyclone overflow passes through a Falcon gravity circuit before returning to the ball mills. Gravity recovery targets native silver, gold, and electrum from the hydrocyclone underflow stream.
Flotation and concentrate handling
Cyclone overflow flows by gravity to a conditioning tank where flotation reagents are added. Conditioned slurry feeds a 5-stage, 30 m³ tank cell rougher flotation circuit. Rougher concentrate advances to a two-stage cleaner circuit; rougher tails discharge to a tailings thickener circuit.
The first cleaner stage consists of a 4-stage, 50 ft³ Denver flotation cell circuit. First cleaner concentrate advances to the second cleaner circuit, which consists of a 2-stage, 50 ft³ Denver flotation cell circuit. Concentrate from the second cleaner circuit is pumped to an 8-metre diameter high rate thickener.
Concentrate thickener underflow at approximately 55% solids is pumped to a 1.5 m × 1.5 m Diemme plate and frame filter press for dewatering. The filter press has 3.4 m³ of filtration volume, equivalent to approximately 6 to 8 tonnes of concentrate. Filtered concentrate is dumped to the cement floor below, reclaimed with a front-end loader, and loaded into trucks for shipment to a refinery. Flotation concentrate is filtered for shipment at approximately 12 tonnes per day.
Tailings
Rougher flotation tails are pumped to a 21-metre diameter high rate Outotec thickener. Tailings are thickened to approximately 60% solids, filtered, and stored in a dry tailings stack facility.
Crushing circuit operation mode
The crusher and screening circuits are designed to run at approximately 100 tonnes per hour until the fine feed bin that feeds the ball mill is full, then shut down.
Major equipment
Major crushing equipment includes a primary jaw crusher (150 horsepower), a grizzly vibratory feeder measuring 46 inches by 16 feet (30 hp), a secondary crusher feed screen (150 hp), and a tertiary crusher (200 hp). Major grinding equipment includes three ball mills: Mill 1 measures 9 by 9 feet; Mill 2 measures 9 by 10 feet; and Mill 3 measures 12 by 14 feet. Major flotation equipment includes 5 rougher circuit 30 ft³ Outotec cells (60 hp), 6 Tipo Wemco 11 ft³ cells (15 hp; 20 hp), and 2 kaiser blowers (100 hp). The plant is located at an elevation of approximately 2,200 metres above sea level, which was considered in equipment and motor design.
Utilities
Electricity is sourced from Distribution Line No. 60 of the Federal Electricity Commission (CFE) supplying 13.8 kV, covering a contracted power of 6.5 MW. On average the plant uses approximately 1,420,000 kilowatt-hours per month. Water is sourced from existing underground workings and recirculated water from the tailings basins; as of the effective date of the report, sufficient water is available for the processing plant and other requirements.
Key reported parameters
| Parameter | Value | Basis |
|---|---|---|
| Historical processing rate (2017 to 2018 records) | 1,500 to 2,000 t/d | Historical operating data |
| Current plant capacity | 1,350 t/d | Reported post-refurbishment capacity |
| Potential increased capacity | 1,584 t/d | Proposed, subject to modifications |
| Primary crusher feed rate | 40 t/h | Design |
| Ball mill feed rate | 37.5 t/h | Design |
| Grind size | 200 mesh (75 μm) | Design |
| Crushing product size | 14,000 microns | Key process design criteria |
| Ball mill feed F80 | 16,000 microns | Key process design criteria |
| Product size P80 | 74 microns | Key process design criteria |
| Bond Work Index (BWi) | 16–21 kWh/t | Key process design criteria |
| Bulk density | 1,800 kg/m³ | Key process design criteria |
| Specific gravity | 2.8 kg/m³ | Key process design criteria |
| Moisture content | 7% | Key process design criteria |
| Flotation slurry density | 33% | Key process design criteria |
| Rougher retention time | 40 minutes | Key process design criteria |
| First cleaner retention time | 21 minutes | Key process design criteria |
| Second cleaner retention time | 17.5 minutes | Key process design criteria |
| Flotation pH | 7.2 | Key process design criteria |
| Concentrate thickener underflow solids | ~55% | Design |
| Tailings thickener underflow solids | ~60% | Design |
| Concentrate filtration rate | ~12 t/d | Design |
| 2024 throughput (January to July) | 220,636 DMT | Actual |
| 2024 average Ag head grade | 48.05 g/t | Actual |
| 2024 average Au head grade | 0.92 g/t | Actual |
| 2024 Ag recovery | 81.3% | Actual |
| 2024 Au recovery | 86.9% | Actual |
| 2024 silver ounces produced | 277,189 oz | Actual |
| 2024 gold ounces produced | 5,736 oz | Actual |
| Contracted power | 6.5 MW | Reported |
| Average monthly electricity use | ~1,420,000 kWh | Reported |
Project website: https://www.gsilver.com/mines/cubo-mines-complex
Technical qualifications
The report notes that the crusher product discharges into the rail car dump hopper at a single point, which limits storage capacity if only the primary crusher is operated as a source of crushed mill feed. The plant capacity of 1,350 tonnes per day is reported as the operational figure following refurbishment; the 1,584 tonnes per day figure is presented as potential and is dependent on implementing specified modifications. The 2024 throughput summary includes material from the El Cubo/El Pingüico Silver Gold Complex and material from other sources.
Source: El Cubo/El Pingüico Silver Gold Complex , 2024 Technical Report, Section 17 Recovery Methods, dated August 1, 2024.
