Source: Mineros S.A (2026)
Website: https://www.mineros.com.co/operations/nicaragua
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Throughput | 1,957 | tpd | Average daily production in 2025 across all three plants; Hemco Plant alone targets 2,200 tpd post-upgrade. |
| Mill Power | 750 | kW | Dominion 11 ft x 14 ft ball mill installed in 2014 as primary mill. |
| Target Grind Size | 75 | μm | P80 of cyclone overflow from grinding circuit. |
| Head Grade | Not specified in Section 17 of the report. | ||
| Recovery % | 89.4 | % | Overall gold recovery for the Hemco Plant in 2025. Combined three-plant recovery was 88.3%. |
| Processing Capacity | 2,200 | tpd | Target grinding capacity after planned modifications to mill configuration and thickener replacements. |
| Energy Consumption | kWh/t | Not provided in the source document. | |
| Water Consumption | m³/t | Not provided in the source document; water is recycled from tailings pond and used in process. | |
| Operating Hours | hours/day | Not specified; continuous operation assumed. |
Overview
Mineros S.A. operates the Hemco Property in Nicaragua’s Región Autónoma de la Costa Caribe Norte, a gold mining complex with three processing plants: the Hemco Plant, La Curva Plant, and Vesmisa Plant. The flagship Hemco Plant processes underground and artisanal feeds and reprocesses tailings from La Curva, using a comprehensive gold recovery flowsheet that includes three-stage crushing, two-stage grinding, agitated cyanide leaching, counter current decantation (CCD), and Merrill-Crowe precipitation. Established historically and continuously upgraded—most notably with a US$1.7 million crusher upgrade in 2019 and a new primary ball mill in 2014—the plant achieved an overall gold recovery of 89.4% in 2025. The significance of the Hemco Plant lies in its ability to handle up to 2,200 tpd after planned grinding circuit modifications, stabilizing throughput that averaged 1,957 tpd in 2025. Key process steps integrate cyanide addition during grinding to initiate leaching early, followed by a nine-tank agitated leach circuit, an eight-thickener CCD system, and a Merrill-Crowe precipitation stage that produces doré bars. These gold recovery methods are optimized for variable feed grades and artisanal sources, making the Hemco Property a benchmark for mid-scale gold processing in Central America.
Key Process Stages
- Stage 1: Crushing – Ore from underground and artisanal miners passes a 14 in. grizzly and a double-deck scalping grizzly producing three size fractions. The +3 in. and +3/8 in. × 3 in. materials feed a primary jaw crusher, followed by secondary and tertiary cone crushers in closed circuit with vibrating screens. The upgraded crushing circuit (2019, US$1.7 million) increased capacity from 100 to 150 tons/hr and includes a new dust collection system.
- Stage 2: Grinding – The grinding circuit consists of one primary ball mill (Dominion 11 ft × 14 ft, 750 kW) and five secondary ball mills configured in parallel. Hydrocyclone classification achieves a cyclone overflow P80 of approximately 75 µm. Cyanide solution is added to the hydrocyclone underflow to initiate gold dissolution. Planned changes will designate Dominion 1 and 2 as primary mills, with Sepro and M5 as regrind mills, achieving a total grinding capacity of 2,200 tpd.
- Stage 3: Leaching – Slurry from grinding is thickened to 45%–50% solids in a primary thickener before entering a series of nine agitated leach tanks (tanks No. 0 through 8). Cyanide and lime maintain pH between 11.0 and 11.5. The first stage (tanks 0–4) is followed by an intermediate thickening step; the underflow enters a second stage (tanks 5–8). Total retention time ensures maximum gold dissolution.
- Stage 4: Counter Current Decantation (CCD) – The CCD circuit comprises eight 50 ft diameter Denver thickeners arranged in two parallel trains of four each. Solution flows counter current to the slurry, washing gold-bearing solution from the solids. Fresh barren solution (from Merrill-Crowe and tailings pond reclaim) is added to the last thickener; overflow moves upstream, while underflow (final tailings) is pumped to the San José tailings facility via two 100 m³/h positive displacement pumps.
- Stage 5: Merrill-Crowe and Refining – Clarified pregnant solution is deoxygenated in a vacuum tower, then mixed with zinc powder to precipitate gold and silver. The precipitate is collected in filter presses, mixed with flux (sodium carbonate, borax, silica sand, fluorspar), and smelted at ~1,350°C in tilting furnaces. The resulting doré bars contain 18%–30% gold and 43%–72% silver, with a silver-to-gold ratio of 3.11 for 2025.
Additional Interesting Data and Summary
Beyond the core recovery circuit, the Hemco Plant includes a dedicated sand washing screen, a laboratory constructed at a cost of US$2.7 million (2020–2021) that processes 800 samples per day using three atomic absorption spectrometers, and a modern tailings disposal system. The San José tailings facility, commissioned in 2017, is fully lined with HDPE, has a design capacity of 27.5 Mt, and a planned life of over 50 years. By 2025, the third expansion lift to 250 MASL was 90% complete, with completion expected by mid-2026. Water is reclaimed from the tailings pond and recycled to the mill or used in a cyanide destruction circuit during the rainy season. The older Aguas Claras facility now serves as a rainwater reservoir, while the Concha Urrutia area (≈2 Mt of tailings) is undergoing closure. Economic investments include US$1.2 million for a new primary ball mill in 2014 and continuous optimization projects. The two satellite plants—La Curva (producing gravity/flotation concentrates sent to Hemco) and Vesmisa (batch processing of high-grade artisanal ore >30 g/t Au at ~250 tonnes/week)—complement Hemco’s throughput. A proposed Porvenir Plant (2,000 tpd) will incorporate Cu-Pb flotation, cyanidation, and zinc flotation with cyanide destruction, targeting a grind size of P80 73 µm. Mineros S.A. has demonstrated a commitment to increasing throughput and recovery through equipment upgrades and process modifications while maintaining environmental compliance with lined tailings storage and water management systems. The Qualified Persons (QPs) from SLR Consulting consider the processing plants to be operating well given the age of the equipment, with no anticipated issues regarding energy, water, or process materials. Future outlook includes the Porvenir plant (subject to feasibility) and continued tailings lift construction, ensuring the Hemco Property remains a significant gold producer in Nicaragua.
Key Processes: Flotation, Cyanidation, Gravity Separation, SAG Mill, Ball Mill, Crushing
Target Commodities: Gold, Silver, Copper, Zinc, Lead
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Hemco Property — 2026 Technical Report
Hemco Property — 2026 Technical Report
| Company | Mineros S.A. |
| Date | 2026 |
| Region | Nicaragua |
| Commodities | Gold, Silver, Copper, Lead, Zinc |
| Mine Type | Underground/Artisanal |
| Throughput | 2,200 tpd (Hemco Plant) |
| Mine Life | 50+ years (TSF Design) |
| Status | Operating |
Executive Summary
This NI 43-101 Technical Report details the processing methods and operational status of the Hemco Property, operated by Mineros S.A. in Nicaragua. The property comprises three active processing plants: the Hemco Plant, the La Curva Plant, and the Vesmisa Plant. The Hemco Plant treats underground and artisanal feeds, as well as reprocessed tailings, with a design throughput of 2,200 tpd. The Vesmisa Plant focuses on artisanal material, while the La Curva Plant produces concentrates for treatment at Hemco. A proposed Porvenir Plant is also outlined, designed for 2,000 tpd with a focus on base metal flotation alongside precious metal recovery.
The primary recovery method for gold and silver at the Hemco and Vesmisa plants involves agitated cyanide leaching followed by the Merrill-Crowe process to produce doré bars. The Porvenir Plant proposal includes a more complex flowsheet incorporating copper-lead and zinc flotation circuits prior to cyanidation and Merrill-Crowe recovery. The report highlights ongoing optimization projects, including crushing and grinding upgrades, and the construction of the San José tailings facility, which has a design life exceeding 50 years.
Overall gold recovery for the Hemco Plant in 2025 was reported at 89.4%, with total recovery across all three plants at 88.3%. The facility utilizes a combination of jaw and cone crushers, ball mills, and SAG mills (for Porvenir), supported by thickening, counter-current decantation, and smelting operations. The report confirms that energy, water, and process material requirements are currently being met without anticipated future issues.
Website: https://www.mineros.com.co/operations/nicaragua
Report Date: 2026
Region: Nicaragua
Project Status: Operating
Commodity: Gold, Silver, Copper, Lead, Zinc
Throughput: 2,200 tpd (Hemco Plant)
Mine Life: 50+ years (TSF Design)
Mine Type: Underground/Artisanal
Ore type:
Hemco Property — 2023 Technical Report
Hemco Property — 2023 Technical Report
| Company | Mineros S.A. |
| Date | 2023 |
| Region | Colombia |
| Commodities | Gold, Silver, Zinc |
| Mine Type | Underground |
| Throughput | 1,750 tpd (Hemco), 140 tpd (Vesmisa) |
| Status | Operating |
Executive Summary
The Hemco Property, operated by Mineros S.A., features multiple processing facilities including the Hemco Plant, Vesmisa Plant, and La Curva Plant, with a proposed Porvenir Plant. The Hemco Plant currently operates at 1,750 tpd with plans to increase to 2,200 tpd by 2026. The processing circuit involves crushing, grinding, agitated cyanide leaching, and Merrill-Crowe precipitation for gold and silver recovery. The Porvenir Plant is proposed for future development with a capacity of 2,000 tpd, incorporating zinc flotation alongside gold and silver recovery.
The operational data indicates consistent throughput between 1,300 and 2,000 tpd from 2016 to 2022. Recovery rates for the Hemco Plant reached 91.1% gold in 2022. The Vesmisa Plant handles artisanal ore at 140 tpd, while La Curva focuses on gravity and flotation concentrates for further processing at Hemco. All plants utilize cyanide-based leaching circuits with Counter Current Decantation (CCD) for solution recovery.
Processing Profile
- Crushing:: Primary Jaw Crusher, Secondary Cone Crusher
- Milling:: Ball Mill (Primary and Secondary)
- Leaching:: Agitated Cyanide Leach
- Recovery:: Merrill-Crowe, Zinc Flotation (Porvenir Phase)
Reports
- entities/Hemco_Mine
- entities/Mineros_SA
Website: https://www.mineros.com.co/operations/nicaragua
Report Date: 2023
Region: Colombia
Project Status: Operating
Commodity: Gold, Silver, Zinc
Throughput: 1,750 tpd (Hemco), 140 tpd (Vesmisa)
Mine Life:
Mine Type: Underground
Ore type:
Hemco Property — 2021 Technical Report
Hemco Property — 2021 Technical Report
| Company | Mineros S.A. |
| Date | 2021 |
| Region | Colombia |
| Commodities | Gold, Silver |
Executive Summary
The Hemco Property, operated by Mineros S.A., features a primary processing facility known as the Hemco Plant. As of the 2021 Technical Report, the plant has achieved a rated capacity of 1,750 tpd, an increase from its 2011 capacity of 750 tpd through various upgrades and operational changes. Average daily production from 2016 to 2021 YTD ranged between 1,319 tpd and 1,710 tpd, demonstrating consistent operational performance.
The processing circuit involves three stages of crushing, two stages of grinding, and a primary thickener. The ore undergoes agitated cyanide leaching in eight tanks followed by Counter Current Decantation (CCD) using eight thickeners. Gold and silver are recovered from the pregnant solution via the Merrill-Crowe process, resulting in doré bars with a silver to gold ratio of 2.75 for 2021 YTD. Overall recovery for the Hemco Plant was 90.6% gold in 2021 YTD.
In addition to the main Hemco Plant, the property includes the Vesmisa Plant, which processes artisanal ore at 140 tpd, and the La Curva Plant, which produces gravity and flotation concentrates for further processing at Hemco. The QP opinion states that the processing plants are operating well despite equipment age, with ongoing optimization projects continuing to meet energy and water requirements.
Reports
- entities/Hemco_Property
Website: https://www.mineros.com.co/operations/nicaragua
Report Date: 2021
Region: Colombia
Project Status:
Commodity: Gold, Silver
Throughput:
Mine Life:
Mine Type:
Ore type:
Hemco Property — 2020 Technical Report
Hemco Property — 2020 Technical Report
Company: Mineros S.A.
Date: 2020
Project: Hemco Property
Region: Not specified
Commodity: Gold, Silver
Executive Summary
This report details the recovery methods employed at the Hemco Plant, operated by Mineros S.A. The Hemco Plant has seen significant upgrades since prior to 2011, increasing its rated capacity from 750 tons per day to the current 1,750 tons per calendar day. The plant utilizes a multi-stage crushing and grinding circuit, followed by agitated cyanide leaching. Gold recovery is further enhanced through a Counter Current Decantation (CCD) process to separate pregnant solutions, which are then treated using the Merrill-Crowe process for gold and silver precipitation.
The milling process includes three crushing stages and two grinding stages, feeding into a primary thickener. The subsequent agitated cyanide leach stage comprises eight tanks, followed by a CCD circuit with eight thickeners. The pregnant solution is then processed using the Merrill-Crowe method to precipitate gold and silver. Smelting of this precipitate yields doré bars. The report also briefly mentions the Vesmisa and La Curva plants, with Vesmisa employing similar processes for artisanal ore, and La Curva producing gravity and flotation concentrates that are then sent to the Hemco Plant for further processing.
Overall gold recovery for the Hemco Plant in 2019 was 89.7%, with an overall recovery of 88.2% across all three processing plants. The report highlights recent upgrades to the crushing area in 2019, which increased capacity. Grinding circuit throughput has also been optimized over the years through various changes in operating procedures and equipment installations. The overall assessment by RPA is that the processing plants are operating well, with throughput increases and ongoing optimization projects contributing to efficient operations.
Website: https://www.mineros.com.co/operations/nicaragua
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