Fuerte Metals' 2026 preliminary economic assessment for the Coffee Gold Project crushes ore in two stages to 50 mm, leaches it year-round on a ridge-top pad and recovers gold in a six-column ADR plant, for 77.5% overall recovery.
The NI 43-101 Technical Report for the 2026 Preliminary Economic Assessment on the Coffee Gold Project, Yukon, Canada, was prepared for Fuerte Metals Corp. with an effective date of March 27, 2026 and a report date of April 8, 2026. The recovery methods section, reviewed by a WSP qualified person, describes crushing, heap leaching and an adsorption, desorption and recovery (ADR) plant designed to treat 7.4 Mt/a at an average head grade of 1.25 g/t Au, with an overall gold recovery of 77.5%.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Report effective date | March 27, 2026 | Not applicable | Report date April 8, 2026; Fuerte Metals Corp. |
| Annual throughput | 7,400,000 | t/a | Nominal 26,909 t/d |
| Average feed grade | 1.25 | g/t Au | Life-of-mine resource |
| Overall gold recovery | 77.5 | % | Not applicable |
| Crushing rate | 1,495 | t/h | 18 h/d, 275 d/a, 75% availability |
| Crushing stages | Gyratory, then cone crusher | Not applicable | Superior MK-III 50-65 and MP800, or equivalent |
| Crushed product | P80 about 50 | mm | Primary product P90 about 145 mm |
| Heap leach pad capacity | About 91 | Mt | Multi-lift ridge-top pad in five stages |
| Leach solution | About 200 ppm NaCN, pH 10.5 to 11.5 | Not applicable | Lime for pH control |
| Pregnant solution flow | 1,100 | m³/h | Two-hour PLS tank storage |
| Carbon columns | 6 in series | Not applicable | 6 t of loaded carbon withdrawn daily |
| Elution | Modified Zadra | Not applicable | 130 to 150°C, 400 to 600 kPag |
| Peak summer power demand | About 9,500 | kVA | Four on-site generators, N+2 |
Overview
The design history reaches back to Goldcorp. Hatch provided engineering and procurement services in 2018. A 2019 update raised plant feed from a nominal 5 Mt/a to 7.4 Mt/a, and in 2024 JDS revised pricing and engineering in an internal study at a similar capacity. The WSP qualified person reviewed the JDS design for the 2026 PEA and states that it is developed enough to meet or exceed PEA requirements, with capacity aligned to the mine plan.
Run-of-mine ore is crushed in two stages to a P80 of about 50 mm and conveyed to a lined heap leach pad. Dilute cyanide is applied by drip emitters, and the pregnant solution drains to tanks in the insulated ADR building, which sits next to and downslope of the heap to minimize pumping. Gold is adsorbed in carbon-in-column (CIC) units, stripped, electrowon and smelted to doré.
Key Process Stages
Crushing. Haul trucks tip into the dump pocket of a gyratory crusher, which reduces ore to a P90 of about 145 mm. A coarse stockpile feeds a cone crusher closed with a sizing screen, giving a P80 of about 50 mm. Lime is added on a transfer conveyor for pH control, and a 10,000 t fine stockpile provides temporary storage if stacking is interrupted. The QP considers the gyratory and cone crusher combination more reliable for this duty than mineral sizers.
Stacking. Transfer and overland conveyors carry the crushed ore to the toe of the pad, where grasshopper conveyors, a bridge conveyor and a radial stacker place it. A dozer spreads each lift.
Heap leaching. The free-draining, ridge-top pad will be developed in five stages to hold about 91 Mt. Its liner is a 2.0 mm LLDPE geomembrane over a geosynthetic clay liner, protected by crushed overliner drain fill. Barren solution at about 200 ppm cyanide travels through two insulated, heat-traced pipelines to the active cell. Pregnant solution flows by gravity through collection pipes and perimeter channels to two pregnant solution tanks.
Carbon adsorption. A trash screen protects six cascading CIC columns. On average, 6 t of loaded carbon is withdrawn daily from the first column, carbon advances forward, and reactivated carbon tops up the sixth column. Final column overflow passes a carbon recovery screen to the barren tank, where cyanide, caustic, antiscalant and make-up water are added.
Acid wash and elution. Loaded carbon is washed with 3% hydrochloric acid, then stripped in a modified Zadra circuit with about 1% sodium hydroxide and 0.1% sodium cyanide at 130 to 150°C and 400 to 600 kPag. One acid wash and elution cycle normally runs each day.
Carbon regeneration. Stripped carbon is dewatered and screened for fines, reactivated in a kiln at 650 to 750°C, quenched and returned to the CIC circuit. New carbon offsets attrition losses.
Refining. Two electrowinning cells deposit gold onto steel wool cathodes in a secure gold room. The sludge is filtered, retorted to remove mercury, fluxed with borax, silica and soda ash, and smelted in an induction furnace to doré, which is flown off site.
Additional Interesting Data and Summary
Several design measures address Yukon winters. No ore is stacked during the coldest period, typically January to March, when the crushing plant shuts down and run-of-mine ore is stockpiled. Leach irrigation continues year-round. A boiler heats the barren solution so that it stays well above freezing as it percolates through the heap, drip lines are buried in winter for insulation, dedicated standby generators back up the barren solution pumps, and the process plant is housed in a heated, insulated building.
Event ponds collect precipitation and freshet water, which is used as process make-up, with any excess sent to water treatment. Raw water comes from a well field next to the Yukon River. Reagents are delivered as sodium cyanide briquettes handled under the International Cyanide Management Code, caustic and hydrochloric acid in 1 t totes, and hydrated lime stored in a 200 t silo.
In summary, the 2026 Coffee PEA is a cold-climate heap leach design. Crushing and stacking run for about nine months of the year, leaching runs continuously with heated solution, and a compact ADR plant recovers gold from 7.4 Mt/a of ore at a design recovery of 77.5%.
Key Processes
- Gyratory primary and cone secondary crushing to P80 50 mm
- Conveyor stacking on a multi-lift, ridge-top heap leach pad
- Drip-irrigated cyanide heap leaching with heated barren solution
- Six-column carbon-in-column adsorption
- Acid wash and modified Zadra elution
- Kiln carbon regeneration
- Electrowinning, mercury retorting and induction smelting to doré
Source: NI 43-101 Technical Report for the 2026 Preliminary Economic Assessment on the Coffee Gold Project, Yukon, Canada, Fuerte Metals Corp., effective date March 27, 2026.
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.
Coffee Gold Project — 2016 Feasibility Study Technical Report
This report presents the feasibility study for the Coffee Gold Project, detailing the proposed open pit mining and heap leach processing operation in west-central Yukon, Canada.
Report context
The Coffee Gold Project is located in west-central Yukon, within the Whitehorse Mining District, Canada, 130 kilometres south of Dawson. The project comprises 3,021 contiguous claims covering an aggregate area of approximately 60,502 hectares. The effective date of this feasibility study technical report is January 6, 2016. The mineral resource estimate was updated sequentially following completion of drilling on the various deposits, with effective dates of March 15, 2015 for Latte, Double Double and Kona, and September 22, 2015 for Supremo. The mineral reserve estimate is based on the mineral resource estimate completed by SIM Geological Inc.
Processing route
Metallurgical Testing Program
Metallurgical testing for the Coffee deposits began in 2011 and continued through 2015. Initial testing was conducted by Inspectorate Exploration & Mining Services Ltd. of Richmond, British Columbia. Since 2013, almost all metallurgical testing for flowsheet development has been performed by Kappes Cassiday and Associates (KCA) of Reno, Nevada. In 2015, comminution test work was completed by ALS Metallurgy of Kamloops, British Columbia.
Ore samples for metallurgical testing have been taken from both bulk surface samples and drill core composites. Testing included column leaching, bottle roll leaching, flotation, column percolation and drain down, multi-element head assay analyses, column leach head and tail assay screen analyses, ball mill work indices, crushing impact, and abrasion indices. In addition to fire assays for gold and silver, analyses for carbon, sulphur, mercury and copper, semi-quantitative analyses for a series of individual elements and whole rock constituents were conducted. No problematic elements were encountered during the head analyses. Silver concentrations are low and any possible silver production will not be economically significant.
The drill core sample collection and compositing was developed to construct samples from multiple drill holes and intervals to fully represent the known areas of the different deposits and facies.
Comminution Testwork Results
Four Bond low impact crusher tests were conducted on the Kona, Double Double, Supremo and Latte composites. The highest value achieved was 11.5 kWh/t from the Latte composite. This is considered soft with respect to impact breakage. Bond abrasion index (AI) tests were conducted on eight samples from all mine areas and the values ranged from 0.029 to 0.097. Samples with an AI of 0.1 or less may be considered mildly abrasive. Bond Rod Mill and Ball Mill Work indices were 12.73 and 15.06 kWh/t respectively for a Latte sulphide composite sample.
Major Test Program Conclusions
Major conclusions from the test program include: Coffee ores generally leach very rapidly with low reagent consumption; ore agglomeration is not required; a trade-off study to evaluate the incremental economics of crushing to a size of 80% passing a 150 mm screen size (P80 of 150 mm) as compared to a P80 of 50 mm determined the P80 of 50 mm to be the optimal option; and cyanide soluble assays from over 14,000 samples confirmed that cyanide soluble recovery is a reliable method to map gold recovery in all known ore zones of the Coffee Gold Project deposit.
To project actual plant operating conditions, laboratory test work gold recoveries were reduced 3% and sodium cyanide consumptions were factored by 25%. However, for the Kona Middle and Lower Transition samples (which represent less than 0.05% of the mineable reserve and where there were not enough drill intervals to assemble a composite), recoveries from the cyanide soluble test work were discounted by 11% and 12% respectively.
The leach profile shows an initial rapid recovery of gold, followed by a slower leaching period to achieve ultimate gold extraction. From KCA test results, a standardized leach profile for all Project ore types were developed based on the solution to solids ratio. The actual period of leaching was adjusted to fit the solution to solids ratio and will be considerably longer than indicated by laboratory columns.
Proposed Crushing and Ore Handling
The process flowsheet includes a two-stage crushing plant followed by a heap leach operation. Run-of-mine ore with an approximate top size of 750 mm will be trucked from the pits and normally dumped directly into the primary jaw crusher at a rate of about 18,000 t/d. A ROM stockpile area with a capacity of approximately 1.5 Mt will allow the stockpiling of ore when the crusher is not running, particularly during the winter months of January through March. The jaw and secondary cone crusher will discharge feed onto the secondary crusher screen. The oversize will return to the secondary cone crusher and the undersize is conveyed to the crushed-ore stockpile. The final target product size is a P80 of 50 mm. Lime will be added to the stockpile feed conveyor for pH control on the heap leach.
Crushed ore will be reclaimed by a front-end loader from a 3,000 t crushed ore stockpile and a fleet of haul trucks will transport the material to the heap leach facility. The crushing plant and haul trucks will operate 275 days per year with no heap leach loading during the coldest period of the year.
Proposed Heap Leach Facility
The heap leach facility consists of a conventional, multi-lift, free-draining ridge-top leach pad, ponds, access roads, and leachate solution distribution and collection piping. Ore will be stacked with trucks on a lined leach pad in nominal 10 m thick lifts. Barren solution will be irrigated onto the heap using drip irrigation. Pregnant (gold-bearing) solution will be collected at the base of the heap leach pad by impermeable membranes and piping. The pregnant solution will flow to the process plant by gravity for gold recovery. The heap is stacked to the ultimate design height of about 80 m (vertically over the leach pad).
The leach pad will be constructed on a graded area along the ridgeline to the west of the process plant and pits. The leach pad will be constructed in stages, with each stage large enough to provide ore capacity for one and a half to three years of operation. The pad will be lined with two liners: a geosynthetic clay liner (GCL) at the base directly overlain by an impermeable collection geomembrane. A network of drainage pipes within a 500-mm thick layer of permeable gravel at the base of the pad will collect and direct the pregnant solution into trunk lines on each flank of the pad and transport it by gravity to the process plant. A series of horizontal trenches or wick drains will be installed beneath the liner system to detect leakage.
Design criteria for the heap leach facility include: nominal design capacity of 47 Mt with expansion capacity to at least 61 Mt; the heap leach pad construction will be phased to optimize capital expenditure, with Stage 1 having a capacity of 7.2 Mt constructed in Year -1, and Stage 2 and beyond having incremental capacities of 8 to 20 Mt each (1.5 to 4 years of operating capacity). The heap leach pad is designed with a base composite liner system and graded to promote free-draining of the pregnant solution to the flanks of the leach pad and then via a pipeline to the plant.
Mitigations to the extreme climate are incorporated to ensure that the heap leach pad does not freeze, including: loading a minimum of 3.5 Mt of ore to the pad, with 30 m of ore depth, in Year -1 in order to maintain thermal integrity; no ore crushing or heap stacking during January through March of each year; barren solution heating November through March of each year with the heating plant designed for 50% surplus capacity; temporary geomembrane covers (thermal covers) will be used beginning in Year 3 to maintain ore and solution temperatures and reduce or eliminate the need for barren solution heating during winter, with the thermal covers also minimizing precipitation infiltration during spring and summer and maximizing runoff for storage or discharge depending on operational water needs; and drip lines will be buried to a depth of at least 1 m before winter, and after Year -1, a backup irrigation area equal to 100% of the primary area will be provided in the event the primary lines freeze.
Solution ponds will not be used in the winter except in upset conditions. Pregnant, barren and wash water will be stored in tanks at the plant (rather than ponds), processed, heated and recirculated back to the heap during the winter period. The heap water balance is designed to minimize make-up water demand from external sources and avoid the need to treat surplus water until near the end of the mine life.
Proposed Processing Plant
The pregnant solution from the heap leach pad will flow by gravity from the heap at a nominal rate of 455 m³/h (design 600 m³/h) by pipe to the pregnant solution tank located in the process plant building. The solution will then be pumped to the carbon adsorption circuit. The carbon adsorption circuit consists of a series of six cascading carbon columns. The barren solution that will discharge from the final carbon column is pumped to the barren solution tank. Cyanide solution, caustic solution and anti-scalant are added to the barren solution as needed. During the colder months, November to the end of March, a boiler will be used to heat the barren solution before it is pumped back to the leach pad.
The loaded carbon from the first carbon column is advanced to the desorption circuit. The loaded carbon, 5 t/d, will be acid washed and gold recovered from the carbon in the strip vessel. The pregnant solution from the strip vessel will flow to the electrowinning circuit. At the conclusion of the strip cycle, the stripped carbon will be thermally regenerated in the 5 t carbon reactivation kiln.
Gold will be plated onto knitted-mesh steel wool cathodes in the electrowinning cells. The gold-bearing sludge and steel wool will be dried in an oven, mixed with fluxes and then smelted to produce gold doré and slag. The doré will be stored in a vault while waiting for transport off site to a refinery for further purification. Slag is processed to remove prills for re-melting in the furnace.
A laboratory facility will be equipped to perform sample preparation and assays by atomic absorption, fire assay, and cyanide (CN) soluble analyses. A metallurgical test work area for process optimization is also included.
Proposed Gold Production Model
The gold production model was developed from a combination of metallurgical testing data, the mine production schedule, the heap leach facility construction sequence (or stacking plan), and the leaching plan for the application of barren solution to the heaps. The gold production model was developed on a quarterly basis for Years -1 through Year 3. At the end of each year when the heaps are no longer loaded with ore there will be an in-process inventory of recoverable gold remaining from two general areas: the recoverable gold in the ore in the heaps that has not been leached to completion and the recoverable gold contained in solution inventories, carbon, and the electrowinning/refining area that has not yet been processed into doré.
At the end of Year 3 the recoverable gold added to the heap and the gold actually produced reach equilibrium and the in-process inventory has stabilized. From Year 4 through to Year 8, the gold produced is the recoverable gold added to the heap with the inventory of gold to be recovered remaining constant. In the third quarter of Year 9 the mined ore and ROM stockpile are depleted. At that time the recovery of the in-process inventory will begin and will continue through Year 10 to completion. It is assumed that 50% of the in-process inventory will be recovered in Year 9 and the remainder in Year 10.
Summary of Gold Recovery by Ore Type
A summary of the distribution of ore types and gold recovery from the proposed mining plan shows that oxide ore represents 82.2% of ore tonnes (38,105 kt), 80.3% of contained gold (1,731 koz) and 84.3% of recoverable gold (1,569 koz). Upper Transition ore represents 11.5% of ore tonnes, 12.5% of contained gold and 11.5% of recoverable gold. Middle Transition ore represents 4.7% of ore tonnes, 5.2% of contained gold and 3.5% of recoverable gold. Lower Transition ore represents 1.6% of ore tonnes, 2.1% of contained gold and 0.6% of recoverable gold.
Key reported parameters
| Parameter | Unit | Design / Proposed Value | Testwork / Historical Basis |
|---|---|---|---|
| Crush product size (P80) | mm | 50 | Trade-off study selected over P80 of 150 mm |
| Heap leach processing rate | Mt/a | 5.0 | Proposed design rate |
| Average feed grade | g/t Au | 1.45 | Proposed mine plan diluted head grade |
| Anticipated overall gold recovery | % | 86.3 | Based on gold production model over LOM |
| Laboratory gold recoveries (Oxide) | % | 88 to 95 (by deposit) | Column leach test results from KCA |
| Feasibility study gold recoveries (Oxide) | % | 85 to 92 (by deposit) | Lab recoveries reduced by 3% |
| Laboratory NaCN consumption (Oxide) | kg/t | 0.6 to 0.87 (by deposit) | Column leach test results |
| Feasibility study NaCN consumption | kg/t | 0.2 (all ore types) | Lab consumption factored by 25% |
| Laboratory lime addition (Oxide) | kg/t | 1.27 to 1.56 (by deposit) | Column leach test results |
| Feasibility study lime addition | kg/t | 1.5 (all ore types) | Testwork basis |
| Nominal pregnant solution flow | m³/h | 455 (design 600) | Proposed design |
| Loaded carbon advance rate | t/d | 5 | Proposed design |
| Bond low impact crush index (Latte) | kWh/t | 11.5 | Testwork (highest of 4 composites) |
| Bond abrasion index range | AI | 0.029 to 0.097 | Testwork on 8 samples (all areas) |
| Bond Rod Mill Work index (Latte sulphide) | kWh/t | 12.73 | Testwork |
| Bond Ball Mill Work index (Latte sulphide) | kWh/t | 15.06 | Testwork |
| Crushing plant operating days | d/a | 275 | Proposed (no heap loading Jan-Mar) |
| ROM stockpile capacity | Mt | ~1.5 | Proposed |
| Crushed ore stockpile capacity | t | 3,000 | Proposed |
| Heap leach pad design capacity | Mt | 47 (expansion to 61) | Proposed design |
| Heap leach pad stage 1 capacity | Mt | 7.2 | Proposed design (Year -1 construction) |
| Heap leach ultimate lift height | m | ~80 | Proposed design |
| Nominal ore lift thickness | m | 10 | Proposed design |
| Instaled power generating capacity | MW | 9 | Proposed design (bi-fuel LNG/diesel capability) |
Project website: https://fuertemetals.com/news/fuerte-completes-acquisition-of-coffee-project/
Technical qualifications
The qualified persons preparing this report are specialists in the fields of geology, exploration, mineral resource and mineral reserve estimation and classification, geotechnical, environmental, permitting, metallurgical testing, mineral processing, processing design, capital and operating cost estimation, and mineral economics. None of the qualified persons or any associates employed in the preparation of this report has any beneficial interest in Kaminak and neither are they insiders, associates, or affiliates. The results of this report are not dependent upon any prior agreements concerning the conclusions to be reached, nor are there any undisclosed understandings concerning any future business dealings between Kaminak and the qualified persons. The qualified persons are being paid a fee for their work in accordance with normal professional consulting practice.
The qualified persons opinions contained herein are based on information provided by Kaminak and others throughout the course of the study. The qualified persons have taken reasonable measures to confirm information provided by others and take responsibility for the information.
Non-qualified person specialists relied upon for specific advice include: Fred Lightner, Kaminak Gold Corp. provided oversight and review of metallurgical testwork, crusing, heap leach facility, the ADR process and gold recovery model; Anthony Crews, P.E. designed the heap leach facility; David Flather, Lorax Environmental Services Ltd. advised on geochemistry and water balance; Jeremy Araki, Onsite Engineering Ltd.; Kevin Jones, Tetra Tech EBA (Tetra) for advice relating to permafrost; and Ernst and Young advised on the tax model.
The gold price and exchange rate used in this study are only estimates based on recent historical performance and there is absolutely no guarantee that they will be realized if the Project is taken into production. The gold price is based on many complex factors and there is no reliable method of predicting long term gold price.
The depth extents of the generated pits were compared to the proportion of resources located within incremental depths of 50 m below surface. The results show that essentially all Indicated Resources and the majority of the Inferred Resources occur at depths where it is considered reasonable that present and future economic conditions would support open pit extraction. As a result, the mineral resources for the Coffee Gold Project are not constrained within a pit shell or a maximum depth below surface because, in the author's opinion, any or all of the Coffee Gold Project resource shows reasonable prospects for eventual economic extraction.
There are no known factors related to environmental, permitting, legal, title, taxation, socio-economic, marketing, or political issues which could materially affect the extraction of the mineral resource.
The most significant potential risks associated with the Project are metallurgical recovery, climatic influences, uncontrolled dilution, operating and capital cost escalation, permitting and environmental compliance, unforeseen schedule delays, changes in regulatory requirements, ability to raise financing and metal price. These risks are common to most mining projects, many of which can be mitigated with adequate engineering, planning and pro-active management.
Source: Coffee Gold Project , 2016 Feasibility Study Technical Report, effective date January 6, 2016, relevant sections including 1.5 Mineral Processing and Metallurgical Testing, 1.6 Mineral Resource Estimate, 1.7 Mineral Reserve Estimate, 1.8 Mining, 1.9 Recovery Methods, 1.10 Project Infrastructure, 1.15 Economic Analysis, 1.16 Conclusions, 2.1 Basis of Feasibility Study, 2.2 Scope of Work, 2.3 Qualified Person Responsibilities and Site Inspections, 3 Reliance on Other Experts, and 4 Property Description and Location.
Coffee Gold Project Gold Recovery: Crushing, Heap Leach & ADR
Coffee Gold Project Gold Recovery: Crushing, Heap Leach & ADR
Source: Unnamed_Company_48 (2026)
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Throughput | 1,495 | t/h | Average hourly crushing rate at 75% availability |
| Mill Power | 9,500 | KVA | Estimated peak summer demand for crushing, conveying, and processing plant |
| Target Grind Size | 50 | mm (P80) | Secondary crushing product size |
| Head Grade | 1.25 | g/t | Average LOM feed grade of gold |
| Recovery % | 77.5 | % | Overall gold recovery |
| Processing Capacity | 7,400,000 | t/a | Annual nominal throughput |
| Energy Consumption | kWh/t | Not specified in source | |
| Water Consumption | m³/t | Not specified; raw water from Yukon River well field | |
| Operating Hours | 18 | hours/day | Crushing plant operating hours, 275 d/a |
Overview
The Coffee Gold Project, located in the Yukon, Canada, employs a robust gold recovery process designed to treat 7.4 million tonnes per annum (Mt/a) with an average head grade of 1.25 g/t gold and an overall recovery rate of 77.5%. The project, supported by engineering firms including Hatch, JDS, and WSP, has undergone multiple design updates since 2018, with the latest internal study in 2024 refining the process for a nominal throughput of 26,909 tonnes per day. The recovery methods center on a two-stage crushing circuit feeding a conventional heap leach operation, followed by an Adsorption, Desorption, and Recovery (ADR) plant to produce gold doré. Crushing utilizes a primary gyratory crusher and secondary cone crusher to achieve a product size P80 of 50 mm. The crushed ore is stacked on a multi-lift heap leach pad where a dilute cyanide solution is applied via drip emitters. Pregnant leach solution (PLS) is collected and processed through a six-stage carbon-in-column (CIC) circuit. Loaded carbon undergoes acid washing, modified Zadra elution, and electrowinning to recover gold. A mercury retort and induction furnace produce doré bars. Winter conditions are mitigated by suspending stacking from January to March, heating barren solution, burying drip emitters, and housing the ADR plant in a heated facility. The process design meets Preliminary Economic Assessment (PEA) requirements and is recommended to advance to the next development phase.
Key Process Stages
- Stage 1: Two-Stage Crushing — ROM material at F80 of 619 mm is fed into a primary gyratory crusher (Superior MK-III 50-65 or equivalent) to achieve a P90 of ~145 mm. The product is conveyed to a coarse stockpile, then reclaimed and fed to a secondary cone crusher (MP800 or equivalent) closed with a sizing screen to produce a final product with P80 of 50 mm. Lime is added on a transfer conveyor to maintain pH. Crushing operates at 1,495 t/h average throughput, 18 h/d, 275 d/a, with a fine stockpile of 10,000 t capacity for temporary storage.
- Stage 2: Heap Leaching and Solution Handling — Crushed ore is conveyed via overland and grasshopper conveyors to a ridge-top heap leach pad with a capacity of 91.5+ million tonnes, stacked in five stages. Drip emitters apply barren solution containing ~200 ppm cyanide at pH 10.5–11.5. Solution percolates by gravity, dissolving gold. A boiler heats barren solution during winter; drip emitters are buried to maintain thermal integrity. PLS flows by gravity through a lined perimeter channel to two pregnant solution tanks in the ADR plant. Meteoric water is managed by lined event ponds with double LLDPE liners and leak detection.
- Stage 3: Carbon-in-Column (CIC) Adsorption — PLS from the storage tank (2-hour holding capacity) is pumped through a single train of six cascading carbon columns, each with 6.0 tonnes of activated carbon. A trash screen protects the columns. Gold is adsorbed onto carbon in counter-current flow. Overflow passes through a recovery screen to capture fines, then gravitates to the barren solution tank where NaCN, NaOH, antiscalant, and make-up water are added. Loaded carbon is withdrawn daily from the first column (6 t/day) and transferred to acid wash and stripping.
- Stage 4: Desorption and Elution — Loaded carbon undergoes acid washing with 3% HCl to remove inorganic foulants. Gold is then stripped using a modified Zadra elution process at 130–150°C and 400–600 kPag with a solution of ~1% NaOH and 0.1% NaCN. The pregnant eluate is cooled and gravity-fed to electrowinning. Stripped carbon is regenerated in a kiln at 650–750°C, quenched, and returned to the CIC circuit. Attritional losses are offset by fresh carbon addition.
- Stage 5: Gold Refining and Doré Production — Pregnant solution from elution flows to two electrowinning cells where gold is deposited on knitted-mesh steel wool cathodes. Loaded cathodes are power-washed to collect gold-bearing sludge, filtered to reduce moisture, and retorted to remove mercury. Retort residue is mixed with fluxes (borax, silica, soda ash) and smelted in an induction furnace to produce doré bullion and slag. Doré bars are stored securely and shipped off-site for final refining.
Additional Interesting Data and Summary
The Coffee Gold Project’s recovery methods are designed for robust performance in Yukon’s extreme climate. The heap leach pad, with a capacity of 91.5+ million tonnes, uses a composite liner system: a 2.0 mm LLDPE geomembrane over a geosynthetic clay liner (GCL) with an objective permeability of 5×10⁻⁹ cm/s. Event ponds employ double LLDPE liners with leak detection and recovery systems (LDRS) to contain meteoric water and prevent environmental release. The ADR plant processes PLS at 1,100 m³/h with a six-stage CIC circuit using 6-tonne carbon columns. Elution follows the modified Zadra process at 130–150°C and 400–600 kPag. Carbon regeneration operates at 650–750°C to maintain activity. Gold refining includes electrowinning with two cells, a mercury retort, and induction furnace smelting to produce doré bars. Reagent handling adheres to the International Cyanide Management Code (ICMC). Sodium cyanide briquettes, sodium hydroxide, hydrochloric acid, antiscalant, and hydrated lime are delivered and stored on-site. Power is supplied by four on-site generators in an N+2 configuration, with a peak summer demand of 9,500 KVA for the processing plant. Water is sourced from a well field near the Yukon River. The design, reviewed by WSP as the Qualified Person, is considered sufficiently developed for PEA level, with crushing equipment (gyratory and cone crushers) selected for reliability over mineral sizers. Winter mitigation strategies—including suspending stacking from January to March, heating barren solution, burying drip emitters, and housing the ADR plant in a heated, insulated facility—ensure year-round operation. The project’s economic significance is underscored by a 77.5% gold recovery rate from a 1.25 g/t head grade at a 7.4 Mt/a throughput. Future development phases will further refine the design to meet Yukon regulatory guidelines for mine waste management. Overall, the Coffee Gold Project’s recovery methods represent a conventional yet climate-adapted approach to gold extraction, with a clear pathway to advancing toward construction.
Key Processes: Heap Leaching, Cyanidation, Gravity Separation, Crushing
Target Commodities: Gold
