Kinsley Project Recovery Methods: Heap Leach and Carbon-in-Columns Design for Oxidized Gold Ore

A look at the proposed processing approach for the Kinsley Project in northeastern Nevada, which would rely on a conventional heap leach operation with a carbon-in-columns recovery plant.

The Kinsley Project is located in the Kinsley Mountains in Elko and White Pine counties, northeastern Nevada, roughly 150 kilometers north-northeast of Ely and 83 kilometers south-southwest of West Wendover. The project is 100% owned by CopAur Minerals Inc., with Kinsley Gold LLC serving as the wholly owned holding entity, and it is currently an advanced exploration and development project with a Preliminary Economic Assessment completed. It would target gold and silver from oxidized material. The project has a history of past production under Alta Gold Co. from 1994 to 1999, and it is envisioned as a restart operation, referred to in the technical report as the KMG Restart. The technical report identifies that the project would employ open pit mining with a conventional heap leach system operating on a 365-day per year, 24-hour per day basis.

Critical Data

Overview

The Kinsley Project recovery approach centers on a conventional heap leach operation treating oxidized material. High grade ore would report to the crushing circuit, while low grade ore would go directly to the heap as run-of-mine feed. The design does not include agglomeration. Lime would be added directly to haul trucks from a silo at the load out area before material is trucked to a prepared permanent leach pad.

The heap leach facility would be constructed in two phases, with the pad foundation preparation, liner installation, and collection piping advanced as the pad expands. The design intent is to minimize capital expenditure by phasing development. The initial phase would include full development of the solution handling system, storm pond, and perimeter diversion ditches prior to commencing ore stacking and leaching. Each stacking stage includes an initial two-year capacity period and one additional two-year period.

Leach solution would be collected from each heap cell through drainpipes under the heap, transported to perimeter piping, and then directed to the pregnant leach solution pond by gravity. From there, solution would be pumped to the carbon recovery circuit.

Key Process Stages

The process flow begins with crushing. Run-of-mine feed passes over a vibrating grizzly with a 3-inch opening. Undersize reports directly to the jaw crusher discharge conveyor. Oversize feeds a jaw crusher set to produce a nominal 7-inch product, which reports to a surge bin. A vibrating feeder beneath the bin feeds a secondary cone crusher with a closed side setting of 2 inches. The secondary circuit runs in open circuit, and the total crushing circuit would achieve a P80 of 2 inches.

Crushed ore and ROM material are stacked on the lined pad by truck dumping in lifts targeted at 6 meters in height. Stacking would be conducted in retreat mode during creation of each leach cell. Each new lift goes on top of the previous lift until the heap reaches its ultimate height of 60 meters, which corresponds to up to 10 lifts.

Once a suitable area has been stacked, the cell would be irrigated with dilute cyanide solution through an emitter-type irrigation system delivering 0.005 gallons per minute per square foot. The primary leach cycle lasts approximately 60 days. After primary leaching, irrigation would be discontinued and advanced to the next cell. No rinse phase is included because of the multiple lift system. Rinsing would be conducted as part of final closure.

The pregnant leach solution flows by gravity from the pad to the PLS pond. From there it is pumped to the recovery plant. The recovery plant uses carbon-in-columns technology. The CIC circuit consists of one train of five vessels, each containing one tonne of carbon. Carbon is advanced counter current to the PLS flow as the first tank in the series reaches its loading limit. The target carbon loading is 3,000 grams per tonne of gold.

Loaded carbon from the first tank is pumped across a loaded carbon screen to a load out system consisting of 1-tonne bulk bags. The screen underflow returns to the PLS flow. Carbon would be stripped by a third party at an external location, and the barren carbon would be returned to the site. The off-site carbon treatment does not include acid washing or thermal carbon regeneration.

Barren solution from the last CIC vessel passes through a carbon safety screen before returning to the heap leach barren solution tank and then being recirculated to the heap with reagent levels adjusted for pH and cyanide. Fine carbon from the screen underflow is stockpiled and sent for separate off-site recovery. Fresh makeup carbon goes to an attrition tank for fines removal before being pumped to a carbon sizing screen. Fine carbon from that screen is captured in a plate and frame filter.

Gold recovery from the loaded carbon takes place through stripping using a process such as ZADRA or the Anglo American Research Laboratory method. The gold is stripped into an enriched solution that reports to an electrowinning circuit, where gold is recovered as sludge and ultimately smelted into doré bars containing gold and silver.

Additional Interesting Data and Summary

The heap leach pad would have a final footprint of approximately 2,388,000 square feet. The design operates as a fully drained system with no leachate storage within the facility. A minimum pad grade of 1 to 2 percent would promote leachate flow toward the collection piping and sump.

The liner system uses an engineered composite double liner design. The components include a 1.6-foot-thick over liner using ore as the material with 2-inch minus and less than 10 percent fines content, an 80-mil LLDPE geomembrane, a 1-foot-thick compacted low permeability soil liner, a leak detection and recovery system, and a 60-mil LLDPE geomembrane. LLDPE was selected for the pad because of its interface friction values, ease of installation in cold climates, performance under high confining stresses, and higher allowable strain where settlement may be an issue. A protective layer of approximately 3 feet of coarse crushed ore or waste would be placed over the liner system to protect it during initial ore placement, and this layer also serves as the drainage layer.

The solution collection system is built from perforated corrugated plastic tubing embedded within the over liner. Lateral collection pipes spaced approximately 16 feet apart feed into collection header pipes, which flow into a main header positioned along the centerline of each pad cell. The main headers terminate at the upstream toe of the perimeter berm at leachate collection ditches. Gate valves on the collection pipes allow solution to be directed to one of three perimeter collection ditches for PLS, barren solution, or storm water.

The leak detection and recovery system captures any solution leaking through the primary geomembrane. It consists of a 1-foot-thick sand layer embedded with 4-inch perforated CPT collection pipes. Recovered leakage conveys into an LDRS sump at the downstream toe. A level-switch controlled submersible pump transfers the recovered solution into the main solution recovery line. The system is subdivided into independently monitored cells separated by small berms, with dedicated collection pipes flowing by gravity at a minimum 0.5 percent slope. Flow rates are continuously monitored before discharge into the sump. Leakage recovery monitoring is done by recording pump operating hours.

Solution storage is provided by three ponds. The event pond handles excess leachate and runoff during rainfall events. Its design capacity of 1,017,757 cubic feet contains the entire estimated surface runoff from the heap leach facility during a 1 in 100-year, 24-hour storm, including a 10 percent additional factor of safety. Overflow is designed to discharge the 1 in 200-year, 24-hour storm event. A pump station would drain the storm volume over approximately ten days.

The pregnant pond would contain up to 7 days of solution at the maximum irrigation rate, with a capacity of about 2,291,572 cubic feet. The barren pond holds 8 hours of solution at 168,790 cubic feet. Excess solution from any of the ponds diverts to the event pond for recycle back to the heap.

The pond liner system uses a double liner design with 60-mil HDPE geomembranes, a 1-foot-thick low permeability soil liner, and a geosynthetic geonet drainage layer. HDPE is specified for the ponds rather than LLDPE because the pond liner would not face high confining stresses from ore stacking, and HDPE offers higher ultraviolet resistance for exposed surfaces. The upslope of the pond embankment would have an additional 1-foot-thick bedding sand layer. No LDRS is required for the storm pond since it operates as a dry facility. If leakage occurs through the pond double liner, water would be conveyed through the geonet layer to a 3-foot-thick drainage blanket underlying the event pond embankment, discharging to a sump.

A surface water management system consisting of perimeter ditches around the heap leach facility would intercept overland runoff and convey surface water away from the active site.

The heap leach configuration depends on the permeability characteristics of the material, the terrain available, and geotechnical site conditions.

Key Processes

• Crushing: single-stage jaw crusher followed by open-circuit secondary cone crusher, achieving P80 of 2 inches
• Agglomeration: not included; lime added directly to haul trucks
• Heap leaching: 6-meter lifts stacked in retreat mode, up to 10 lifts total, 60-day primary leach cycle with dilute cyanide irrigation
• Recovery: carbon-in-columns circuit with five vessels, counter-current carbon advancement, target loading of 3,000 g/t gold
• Carbon regeneration: external stripping by third party; no acid washing or thermal regeneration on site
• Electrowinning and smelting: gold recovered from strip solution as sludge, smelted to doré
• Solution management: pregnant, barren, and event ponds with double liner systems and leak detection
• Liner system: composite double liner with LLDPE geomembranes for pad, HDPE for ponds
• Leak detection: LDRS with sand layer, perforated pipes, and monitored collection cells

Source: Kinsley Project Preliminary Economic Assessment NI 43-101 Technical Report, July 10, 2026. Project website: Kinsley Project