Converse Project Heap Leach Gold Recovery Methods

Source: Unnamed_Company_17 (2026)
Website: https://roxmoreresources.com/projects/converse-project

Critical Data

Overview

Roxmore Resources Inc. is advancing the Converse Project, a large-scale gold and silver heap leach operation located in Nevada, USA. The Preliminary Economic Assessment (PEA) effective May 2026, prepared by SLR Consulting, outlines a robust recovery process designed to treat 61,644 tonnes per day of mineralized material from an open pit mine. The project, with a minable resource of 299.8 million tonnes and an estimated 14.5-year mine life, employs cyanide heap leaching as the primary recovery method. The process begins with three-stage crushing to achieve a product size of 80% passing 6.3 mm, followed by agglomeration with cement to enhance heap permeability. The agglomerated ore is stacked in 10-meter lifts on a multi-lift leach pad and irrigated with dilute sodium cyanide solution. Gold and silver values are dissolved in the heap, collected as pregnant leach solution, and recovered via a carbon-in-column adsorption circuit. Loaded carbon is stripped in a high-temperature elution process, and precious metals are electrowon, retorted to remove mercury, and smelted into doré bars. The entire facility is designed for zero-discharge, with comprehensive pond storage and a water balance that accounts for variable precipitation and evaporation. This integrated heap leach recovery system is central to the project’s economic viability and environmental stewardship.

Key Process Stages

• Stage 1: Crushing – Run-of-mine material is fed into a primary gyratory crusher with a 165 mm discharge setting, then conveyed to a coarse ore stockpile. Secondary and tertiary crushing uses screens, standard cone crushers, and two HPGR crushers in open circuit to produce a final product 80% passing 6.3 mm. The circuit operates 365 days per year, 24 hours per day, at an average throughput of 61,644 tpd with 75% availability. Water sprays and metal detectors ensure dust control and equipment protection.
• Stage 2: Reclamation and Conveyor Stacking – Crushed material is stockpiled and reclaimed via three belt feeders, each feeding an agglomeration drum. Cement from silos is metered onto the feed conveyors for binding fine particles. Three parallel agglomeration drums mix crushed ore, cement, and barren process solution to produce stable agglomerates. The agglomerated material is conveyed via an overland conveyor to a mobile stacking system consisting of up to 28 grasshopper conveyors, a horizontal index conveyor, and a radial stacker for placement in 10 m lifts. Each lift is cross-ripped before stacking the next to maintain permeability.
• Stage 3: Leach Pad Design – The single-use, multi-lift leach pad has a total capacity of 310 Mt across eight lifts with a maximum height of 80 m. The liner system from top to bottom comprises 600 mm of overliner gravel, a 2 mm LLDPE geomembrane, 600 mm of compacted soil liner (1×10⁻⁷ cm/s permeability), and prepared subgrade. Perforated solution collection pipes are installed on the geomembrane and covered with overliner. Pad construction is phased, with an initial lined area of 1.1 Mm² and a LOM area of 3.4 Mm². The design meets International Cyanide Code and NDEP standards.
• Stage 4: Solution Application and Storage – Barren solution containing 200–300 ppm NaCN is applied to the heap via buried drip emitters at a rate of 10 L/h/m². The leach cycle is 120 days. Pregnant solution drains by gravity to a lined pregnant solution pond. Process solution storage includes pregnant (210,500 m³), barren (78,600 m³), and event/overflow (444,250 m³) ponds, each with composite HDPE liners and leak detection. The system is designed for a 100-year, 24-hour storm event (64 mm) plus highest recorded snowfall (838 mm). Water balance modeling shows a net annual deficit requiring make-up water of 177–219 m³/h, with zero discharge.
• Stage 5: Recovery Plant (ADR) – Pregnant leach solution from the heap is pumped to a carbon adsorption circuit comprising four trains of five cascade-type open-top columns. Gold is adsorbed onto activated carbon. Loaded carbon is acid washed to remove scale, then desorbed in a high-temperature elution circuit coupled to electrowinning. The resulting precious metal sludge is retorted to recover mercury and smelted to produce doré bars. All carbon is thermally reactivated in a rotary kiln after each elution. The recovery plant is semi-automatic with local HMI panels and a main PLC for monitoring.

Additional Interesting Data and Summary

The Converse Project’s recovery methods are supported by extensive metallurgical test work reviewed by KCA and detailed process design criteria. The process plant is designed to handle 22.5 Mtpa (61,644 tpd) with a three-stage crushing circuit operating at 75% availability, producing a final crush size of 80% passing 6.3 mm. Cement consumption averages 6 kg/t for agglomeration, while sodium cyanide consumption averages 0.64 kg/t over the mine life. The heap leach pad spans eight lifts with a total capacity of 310 Mt, a maximum stacking height of 80 m, and a leaching cycle of 120 days. Solution is applied at 10 L/h/m² via buried drip emitters, totaling a nominal irrigation rate of 4,020 m³/h. The pad and pond liner systems are designed to meet International Cyanide Code and NDEP standards, with double HDPE geomembrane liners and leak detection beneath ponds. Storm event storage accommodates a 100-year, 24-hour event (64 mm) plus 838 mm of snowfall water equivalent. Water balance modeling for average, wet, and dry years indicates a net annual deficit, requiring make-up water of 177–219 m³/h (max monthly 305 m³/h). The carbon adsorption circuit uses four trains of five cascade columns; loaded carbon is desorbed via high-temperature elution and electrowinning. Mercury is recovered in a retort, and the final product is doré bars. The recovery plant operates semi-automatically with PLC control. Environmental considerations include zero-discharge design, storm event ponds, and protective liners to prevent groundwater impact. Economically, the 70.9% gold recovery rate is key to project viability. Sustainability initiatives include grid power supply and heat-traced piping for winter operations. The future outlook is positive, with the PEA demonstrating a 14.5-year mine life and potential for optimization. Overall, the Converse Project’s recovery methods are technically robust and environmentally responsible, positioning Roxmore Resources Inc. for successful gold and silver production in Nevada.

Key Processes: Heap Leaching, Cyanidation, Gravity Separation, Crushing

Target Commodities: Gold, Silver