The Wind Mountain gold-silver project in Nevada would use run-of-mine cyanide heap leaching followed by Merrill-Crowe precipitation, a flow sheet familiar to the site from historical operations between 1989 and 1999.
Wind Mountain is a gold-silver project in Nevada owned by Bravada Gold Corporation through its wholly owned subsidiary Rio Fortuna Exploration (U.S.), Inc. The project is at the preliminary economic assessment stage, with recovery methods described for a processing rate of 25,000 tons per day. The site previously operated from 1989 to 1999 using the same process concept now proposed. The technical report carrying this information carries an effective date of October 15, 2026. Construction timing is not stated in the recovery methods section of the report.
Critical Data
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Daily processing rate | 25,000 | tpd | Design value from mine plan |
| Operating days per year | 360 | days | Design value |
| Annual processing rate | 9,000,000 | tpa | Calculated from daily rate and operating days |
| Operating hours per day | 24 | hours | Design value |
| Heap stacking rate | 1,042 | tph | Calculated from daily rate and operating hours |
| Au grade, life of mine average | 0.011 | oz/ton | From mine plan |
| Ag grade, life of mine average | 0.263 | oz/ton | From mine plan |
| Au recovery, oxide | 62.0 | % | Historical operations and test work |
| Ag recovery, oxide | 15.0 | % | Test work |
| Au/Ag recovery, mixed (transition) | 20.0 / 0.0 | % | From previous PEA, to be evaluated |
| Cyanide consumption | 1.0 | lb/ton | Test work |
| Lime addition to ore | 3.0 | lb/ton | Test work |
| Stacking height per lift | 27 | ft | Design value |
| Application rate | 0.004 | gpm/ft² | Design value |
| Leach cycle | 90 | days | Design value |
| Total heap cycle | 150 | days | Design value |
| Nominal solution flow to Merrill-Crowe plant | 6,070 | gpm | Calculated |
| Nominal area under leach | 1.5 | million ft² | Approximately 35 acres |
| Installed process power | 7,500 | horsepower | Estimate |
| Operating load | 4,800 | kW | Estimate |
| Annual power consumption | 41.9 | million kWh | Estimate |
| Power consumption per ton | 4.7 | kWh/ton | Estimate |
| Power cost | 0.0864 | USD/kWh | Estimate |
| Process operations and maintenance personnel | 41 | persons | Estimate |
| Total tons placed, life of mine | 100.2 | million tons | From production schedule |
| Au placed, life of mine | 738,000 | oz | From production schedule |
| Ag placed, life of mine | 21,066,000 | oz | From production schedule |
| Au recovered, life of mine | 457,000 | oz | From production schedule |
| Ag recovered, life of mine | 3,151,000 | oz | From production schedule |
| Cumulative Au recovery | 61.9 | % | shows oxide, mixed, and unoxidized blend |
| Cumulative Ag recovery | 15.0 | % | From production schedule |
| Average silver-to-gold grade ratio | 24:1 | ratio | From mine schedule |
| Recovered silver relative to gold | 5.6 | times | Ratio of recovered metals |
| Lime silo capacity | 120 | tons | 3 days storage |
| Cyanide storage tank | 9 ft × 24 ft | ft | With mixer |
| Body feed tank | 9 ft × 24 | ft | With mixer |
| Precoat tank | 10 ft × 24 | ft | With mixer |
| Deaeration tower capacity | 7,000 | gpm | Estimated |
| Precipitate filter press rating | 2,500 | gpm | Each of three |
| Clarifier leaf filter area | 2,000 | ft² | Each of three |
| Barren solution pump rating | 6,250 | gpm at 200 ft | Vertical turbine, 316 SS |
| PLS transfer pump rating | 8,000 | gpm | Two units |
| Clarified solution pump rating | 8,000 | gpm | Two units |
| Filter press feed pump rating | 8,000 | gpm | Two units |
| Fresh water pump rating | 1,000 | gpm | Two units |
| Fire water pumps | 1,000 | gpm | Three units, electric and diesel |
| Mercury retort volume | 13 | ft³ | Each of two |
| Induction furnace power | 216 | kW | One unit |
| Barren solution pump head | 200 | ft | Includes 58 ft for drip emitters, 100 ft static, 36 ft friction |
| PLS transfer pump head | 60 | ft | Lift from pond to plant |
| Clarified solution pump head | 150 | ft | Set by 40 psi end-of-cycle filter pressure |
| Filter press feed pump head | 160 | ft | Set by 50 psi end-of-cycle pressure and vacuum |
Overview
The recovery method for Wind Mountain is conventional run-of-mine cyanide heap leaching followed by Merrill-Crowe solution processing for gold and silver recovery. The same process was used at the site during historical production, with the difference that all leach material will be placed as run-of-mine ore. Merrill-Crowe was selected over carbon adsorption because of the silver content in the leach solutions. The mine schedule carries an average silver-to-gold grade ratio around 24 to 1, and recovered silver runs approximately 5.6 times recovered gold.
The process design is built around a production rate of 25,000 tons per day with metal recoveries of 65% for gold and 15% for silver for oxide material. The actual cumulative recovery in the production schedule lands at 61.9% for gold and 15.0% for silver once the blend of oxide, mixed, and unoxidized material is accounted for.
Process hydrology has not been completed. For the PEA, sufficient water for processing is assumed to be available. A site water balance covering make-up water requirements and pond sizing for storm events and drain-down is required at the next study stage.
Key Process Stages
The leach pad is built with suitable linings and a solution collection network of perforated piping. Over-liner material protects the liner and collection pipes while allowing solution flow to the collection system. Mine haul trucks dump run-of-mine leach material directly in place. Before placement, each truck drives under the lime silo for lime addition to maintain a protective pH. A dozer maintains the surface gradient of each lift, and ore is stacked in 27-foot lifts. The stacked material is ripped by dozer to minimize compaction and promote solution percolation. Clay-rich material identified during mining is segregated and sent to waste dumps.
After pad preparation, the irrigation system is placed on the ore. Dilute sodium cyanide solution called barren solution is applied to the surface through header pipes and drip irrigation lines at 0.004 gpm per square foot. Barren solution is pumped from two 17,000-gallon tanks by vertical turbine pumps rated at 6,250 gpm at 200 feet of head. The solution percolates through the stacked ore, leaching gold and silver, and is collected through the collection system and sent to the pregnant leach solution pond. Leaching works most efficiently when solution pH sits between 10 and 10.5.
Pregnant leach solution transfers from the pond to the Merrill-Crowe plant by two 8,000-gpm pumps. At the plant, clarified solution pumps move the solution from the PLS tanks through three pressure leaf clarifier filters that remove suspended solids. Two operating filters handle 100% of process throughput while the third filter is being cleaned. Diatomaceous earth pre-coats the clarifiers. Clarified PLS flows to the deaeration tower where dissolved oxygen is removed under vacuum.
Zinc dust is added to the deaerated solution by the zinc feeder. The zinc reacts with gold and silver cyanide complexes to precipitate the precious metals. Pre-coated plate and frame filter presses separate the precipitate from solution. After metal removal, the solution returns to the barren solution tanks where sodium cyanide is added to maintain cyanide concentration before recycling to the heap. Fresh water replaces solution lost to ore wetting and evaporation.
Precipitate removed from the filter presses goes into trays and then into mercury retorts to remove moisture and mercury. A mercury condenser captures mercury vapors for collection and off-site shipment. Vapors not condensed pass through a scrubber filled with sulfur-impregnated carbon. Retorting is followed by batch flux smelting in an induction furnace to produce doré bars for shipment to a refinery.
The process production schedule applies no recovery in the month material is placed, which allows time for placement and preparation before leaching. The following months allow for 85%, 7%, 5%, and 3% of total recoverable ounces. That lag spreads recovery over approximately 150 days when placement time is included. The lag is consistent with column test kinetics and with historical operations, which recovered roughly 14% of gold after ore placement ended. WMMI monthly reports show drain-down and rinsing contributed approximately 12% of total gold production.
Additional Interesting Data and Summary
The process facilities include a single large leach pad, pregnant and event ponds, the Merrill-Crowe plant and refinery, reagent storage, and fresh water and fire water systems. Facility design has not been completed and is shown conceptually in the report. Pump heads, motor sizes, and the number of operating pumps will be confirmed with vendors at the next study stage.
Reagent consumptions in the model are 0.5 kg/t sodium cyanide, 1.5 kg/t lime, 0.002 kg/t zinc dust, and 0.01 kg/t anti-scalant. Diatomaceous earth and refinery fluxes are carried as an allowance. Consumptions are based on test work data and industry norms.
The qualified person for this section considers the recovery methods appropriate for the project at a PEA level of study. ROM cyanide heap leaching followed by Merrill-Crowe precipitation is a conventional and well-established process for low-grade oxide gold-silver deposits in Nevada. Historical production records, WMMI monthly operating reports, and column test work support the process selection, reagent consumptions, and recovery lag used in the production schedule.
Risks identified by the qualified person include recoveries for mixed and unoxidized material carried forward from the previous PEA without supporting test work. Unoxidized material is placed on the lined pad because it may be potentially acid generating. Size-dependent recovery is another risk, with 2012 column tests showing North Wind pit material sensitive to particle size while Breeze pit material is not. Run-of-mine recovery from the Wind pit may run lower than the deposit average, and crushing will be evaluated at sizes no finer than a P80 of 3/8 inch. Heap permeability risk comes from clay, particularly in the Breeze area, requiring segregation of clay-rich material during mining and load-permeability testing. Process water has not been confirmed through a site water balance. Mercury leaches with gold and silver and reports to the precipitate, with retorting, mercury collection, and emission controls included in the design and subject to air-quality permitting. Spent ore will require geochemical characterization and rinsing or neutralization at closure.
Key Processes
- Run-of-mine cyanide heap leaching for gold and silver recovery
- Lime addition to ore before placement for pH protection
- Drip irrigation application of barren solution at 0.004 gpm/ft²
- Solution collection through perforated piping to pregnant leach solution pond
- Pressure leaf clarification with diatomaceous earth pre-coat
- Vacuum deaeration to remove dissolved oxygen
- Zinc dust precipitation of gold and silver
- Plate and frame filter press separation of precipitate
- Mercury retorting with condenser and sulfur-impregnated carbon scrubber
- Batch flux smelting in induction furnace to produce doré
- Barren solution recycling with sodium cyanide replenishment
Source: 2026 PRELIMINARY ECONOMIC ASSESSMENT WIND MOUNTAIN GOLD-SILVER PROJECT, NEVADA, October 15, 2026. Project website: Wind Mountain Gold-Silver Project
