Overview
Nestled in the mineral-rich landscape of Pinal County, Arizona, the Cactus Mine Project stands as a significant development in the North American copper industry. Operated by the Arizona Sonoran Copper Company Inc. (ASCU), this project aims to revitalize a historic mining district near Casa Grande into a major, modern producer of high-purity copper cathode. The project’s significance is underscored by a comprehensive Pre-Feasibility Study (PFS) detailed in an NI 43-101 Technical Report, dated October 2025, which outlines a robust plan for sustainable copper extraction. The Cactus Mine is designed to process a substantial 28 million dry tons of ore annually from two primary open pits—Parks/Salyer and Cactus West—which contain a mix of oxide, enriched, and primary sulfide copper mineralization. Unlike traditional concentrator-based operations, Cactus will employ a large-scale heap leach, solvent extraction, and electrowinning (HL-SX-EW) circuit, a hydrometallurgical method renowned for its lower energy intensity and cost-effectiveness for certain ore types. This strategic choice positions the project to be a competitive supplier of LME Grade A copper cathode, a critical material for the global energy transition, including electric vehicles and renewable infrastructure. The planned phased expansion, doubling cathode production from 70,000 to 140,000 tons per year, highlights the project’s scale and long-term vision within Arizona’s established and geopolitically stable mining jurisdiction.
Key Process Stages
The Cactus Mine mineral processing circuit is a classic example of modern hydrometallurgy applied to copper extraction. The flowsheet is elegantly straightforward yet engineered for high efficiency and reliability, moving from coarse rock to finished cathode through a series of integrated stages. The design prioritizes robust equipment selection and operational flexibility to handle the projected feed over a 20-year mine life.
- Stage 1: Primary & Secondary Crushing: Run-of-Mine (ROM) ore, with a maximum size of 24 inches, is first reduced by a high-capacity primary sizer crusher operating at 4,298 dry tons per hour. The crushed material is then screened. The undersize is conveyed directly to load-out, while the oversize reports to the secondary crushing circuit. This circuit features four standard cone crushers and four double-deck vibrating screens in a closed configuration to ensure a tightly controlled final product size. The target is an 80% passing (P80) size of 3/4 inch (19 mm), which optimizes permeability and leach kinetics in the subsequent heap leach.
- Stage 2: Heap Leaching: The crushed ore is trucked to a lined Heap Leach Pad (HLP). Material is placed in 30-foot lifts, with a maximum ultimate heap height of 250 feet. A raffinate solution—a dilute sulfuric acid—is irrigated over the heap via buried drip emitters to minimize evaporation. As the solution percolates through the ore, it dissolves the copper. Critical to the process is the injection of air via blowers at the base of every second lift to ensure sufficient oxygen is present for the leaching reactions, especially for sulfide minerals. The copper-laden solution, now called Pregnant Leach Solution (PLS), drains by gravity to a collection pond.
- Stage 3: Solvent Extraction (SX): The PLS is pumped to the SX plant at a design flow rate of 21,800 gallons per minute. Here, copper is selectively transferred from the aqueous PLS into an organic extractant solution through a series of mixer-settlers. The plant is designed to operate in a series-parallel configuration with three extraction stages and one stripping stage. This process purifies and concentrates the copper, producing a “loaded organic” stream and a depleted aqueous stream (raffinate). The raffinate is re-acidified and recirculated back to the heap leach, creating a closed-loop solution management system.
- Stage 4: Electrowinning (EW): In the electrowinning tankhouse, copper is plated onto stainless steel cathode blanks from the rich electrolyte derived from the SX strip stage. The initial circuit comprises 102 cells, each containing 85 cathodes and 84 lead-alloy anodes, operating at a current density of 29 amps per square foot. A second, identical circuit will be added between years 3 and 4 to double capacity. Additives like cobalt sulfate (to control anode corrosion) and guar (a smoothing agent) are used to ensure the production of high-quality, market-grade cathode. The final product is a 99.99% pure copper cathode, stripped mechanically, bundled, and prepared for shipment.
- Stage 5: Reagent & Utility Systems: This supporting stage is critical for operations. It includes the bulk storage and dosing of concentrated sulfuric acid (average 253 tons/day), management of SX reagents (extractant, diluent), and EW additives. The circuit also integrates comprehensive water management, drawing on a secured supply from existing rights and pit dewatering, and a significant power distribution network to drive the entire 59.7 MW process plant.
Critical Data
The following table summarizes the key technical and operational parameters that define the scale and efficiency of the Cactus Mine processing circuit, as outlined in the 2025 Pre-Feasibility Study.
| Parameter | Value | Unit | Notes |
|---|---|---|---|
| Annual Ore Throughput | 28,000,000 | dry tons/year | Design basis for crushing and heap leach. |
| Daily Ore Throughput | 76,712 | tons/day | Based on 365 operating days per year. |
| Target Crushed Product Size (P80) | 19 | mm (3/4″) | Final product from secondary crushing circuit. |
| LOM Copper Recovery | 75 | % | Life-of-Mine weighted average recovery of total copper. |
| Peak Cathode Production Capacity | 140,000 | tons/year | After expansion in Year 4 (from initial 70,000 t/y). |
| Process Plant Connected Power | 59,654 | kW | Total for crushing, HLP, SX-EW, water, and air systems. |
| Specific Power Consumption | 1.87 | kWh/lb Cu | At full production of 140,000 st/yr cathode. |
| Sulfuric Acid Consumption (Net, LOM Avg) | 7 | lb H2SO4/ton ore | Net acid added to the raffinate circuit. |
| PLS Flow to SX Plant | 21,800 | gallons per minute (gpm) | Design flow rate for solvent extraction. |
Additional Interesting Data and Summary
The Cactus Mine Project is not only defined by its impressive throughput but also by the detailed engineering and sustainability considerations embedded in its design. The metallurgical projection forecasts a variable but strong production profile, reaching the full 140,000-ton-per-year cathode capacity by Year 5 and sustaining it through periods of higher-grade ore. The average feed grade over the first 15 years is a respectable 0.605% CuT, with a life-of-mine average of 0.517% CuT. A key efficiency metric is the net acid consumption, which is projected at a low 0.9 pounds of sulfuric acid per pound of copper produced over the LOM, reflecting favorable ore mineralogy and efficient leaching conditions.
From an environmental and operational standpoint, the project incorporates several notable features. Water consumption is carefully modeled on a monthly basis, with peak usage during the hot summer months (e.g., ~4.1 million gallons per day in July). The use of buried drip irrigation on the heap leach pad is a specific design choice to drastically reduce evaporative losses—a critical consideration in arid Arizona. The connected power demand of nearly 60 MW highlights the scale of the operation, yet the HL-SX-EW process is generally less energy-intensive per pound of copper than conventional milling and smelting. The report also details comprehensive reagent consumption rates, from SX extractant (0.34 gallons per ton of copper) to EW additives like cobalt sulfate.
Economically, the project represents a major investment in Arizona’s copper belt, with the phased expansion providing a pathway to scale production responsibly. The use of the HL-SX-EW method allows for a smaller physical footprint for the processing plant compared to a concentrator and eliminates the need for a tailings storage facility, as the leached ore (spent heap) remains stacked on the lined pad. This technical approach, combined with the project’s location in a mining-friendly jurisdiction with established infrastructure, positions the Cactus Mine as a strategically important, future-ready source of essential copper for the global market.
Source: NI 43-101 Technical Report | Pre-Feasibility Study | Project: Cactus Mine Project | Date: October 2025
Further Reading
Technical report and processing history
The following archived source profiles have been consolidated here to preserve the project’s processing history and study context.
Cactus Mine Project — 2025 Pre-Feasibility Study Technical Report
Cactus Mine Project — 2025 Pre-Feasibility Study Technical Report
| Company | Not Specified |
| Date | 2025 |
| Region | Not Specified |
| Commodities | Copper |
| Mine Type | Open Pit |
| Throughput | 28,000,000 t/y (76,712 t/d) |
| Mine Life | 20 years |
| Annual Production | 70,000 – 140,000 t/y Cu Cathode |
| Status | Development |
Executive Summary
This 2025 Pre-Feasibility Study outlines the recovery methods for the Cactus Mine Project, focusing on a heap leach and solvent extraction-electrowinning (SX-EW) process. The design basis supports an annual operating throughput of 28,000,000 dry tons of ore, with an initial copper cathode production of 70,000 tons per year, expanding to 140,000 tons per year between years three and four. The project targets LME Grade A quality standards for copper cathodes.
Feed material is sourced from the Parks/Salyer and Cactus West open pits, containing oxide, enriched, and primary sulfide material. Metallurgical tests confirm suitability for heap leaching using dilute sulfuric acid. The process involves a two-stage crushing circuit feeding a lined heap leach pad (HLP), followed by solvent extraction and electrowinning to produce pure copper cathodes.
The project operates on a 20-year mine life with a 365-day operating schedule. Key operational parameters include a crushing throughput of 4,298 dry t/h and a heap leach ultimate height of 250 ft. The SX-EW plant is designed with three extraction settlers and a tank house, with power requirements estimated at approximately 59.7 MW at full production capacity.
Processing Profile
- Crushing: Primary Sizer, Secondary Cone Crushers (4 units)
- Milling: N/A
- Flotation: N/A
- Leaching: Heap Leach (HLP) with Sulfuric Acid
- Refining: Solvent Extraction (SX) and Electrowinning (EW)
Website: https://arizonasonoran.com/news-releases/arizona-sonoran-initiates-2026-work-plan-to-advance-cactus-and-2025-recap/
Report Date: 2025
Region: Not Specified
Project Status: Development
Commodity: Copper
Throughput: 28,000,000 t/y (76,712 t/d)
Mine Life: 20 years
Mine Type: Open Pit
Ore type:
Cactus Mine Project — 2025 Pre-Feasibility Study
Cactus Mine Project — 2025 Pre-Feasibility Study
| Company | AGP |
| Mine | Cactus Mine |
| Date | 2025-11-17 |
| Region | Not Specified |
| Commodities | Copper |
| Mine Type | Open Pit |
| Throughput | 28,000,000 t/y |
| Mine Life | 20 years |
| Annual Production | 140,000 t/y |
| Status | Development |
Executive Summary
The 2025 Pre-Feasibility Study (PFS) for the Cactus Mine Project outlines a design basis for material handling and processing equipment targeting an annual operating throughput of 28,000,000 dry tons of ore. The facility is designed to produce 70,000 tons of copper cathode per year initially, with an expansion planned between years three and four to double capacity to 140,000 tons per year. The project utilizes feed material from the Parks/Salyer and Cactus West open pits, which contain oxide, enriched, and primary sulfide material suitable for heap leaching.
The metallurgical testing confirms the materials are suitable for treatment in a heap leach, solvent extraction, and electrowinning (SX-EW) process facility. The design aims to produce copper cathodes meeting LME Grade A quality standards (ASTM B115-10 – Cathode Grade 1). The process plant includes a two-stage crushing and screening plant ahead of the Heap Leach Pad (HLP), followed by a solvent extraction and electrowinning plant.
Operational parameters include a crushing throughput of 4,298 dry t/h and a final product size of 80 percent passing 3/4 inch. The heap leach circuit utilizes dilute sulfuric acid irrigation with air injection to facilitate copper dissolution. The SX-EW plant features a series-parallel configuration with an initial capacity of 70,000 t/y expanding to 140,000 t/y. The overall plant utilization is targeted at 85% for crushing and 96% for SX-EW.
Processing Profile
- Crushing: Primary Sizer, Secondary Cone Crushers
- Milling: N/A
- Flotation: N/A
- Leaching: Heap Leach (HLP) with Sulfuric Acid
- SX-EW: Solvent Extraction and Electrowinning
Website: https://arizonasonoran.com/projects/cactus-mine-project/overview/
Report Date: 2025-11-17
Region: Not Specified
Project Status: Development
Commodity: Copper
Throughput: 28,000,000 t/y
Mine Life: 20 years
Mine Type: Open Pit
Ore type:
Cactus Mine Project — 2025 Technical Report
Cactus Mine Project — 2025 Technical Report
| Company | Cactus Mine Project |
| Date | 2025 |
| Commodities | Copper |
| Mine Type | Open Pit |
| Throughput | 28,000,000 t/y |
| Mine Life | 20 years |
| Annual Production | 140,000 t/y Cu |
| Status | Development |
Executive Summary
This Pre-Feasibility Study (PFS) outlines the recovery methods for the Cactus Mine Project, focusing on a heap leach, solvent extraction, and electrowinning (SX-EW) process to produce copper cathodes. The design basis for the 2025 study assumes an annual operating throughput of 28,000,000 dry tons of ore placed on the Heap Leach Pad (HLP). The initial cathode production capacity is set at 70,000 tons per year, with an expansion planned between years three and four to double capacity to 140,000 tons per year.
Feed material is sourced from the Parks/Salyer and Cactus West open pits, containing oxide, enriched, and primary sulfide material. Metallurgical tests confirm suitability for the proposed SX-EW process to produce LME Grade A quality copper cathodes. The process plant includes a two-stage crushing and screening circuit, followed by the HLP, solvent extraction, and electrowinning facilities. The project operates on a 365-day schedule with two 12-hour shifts per day.
The metallurgical projection indicates a Life of Mine (LOM) weighted average copper grade of 0.517% CuT, with an overall LOM copper recovery of 75%. The process design criteria account for sulfuric acid consumption, power requirements, and reagent usage, ensuring a robust operational framework for the development phase of the mine.
Website: https://arizonasonoran.com/projects/cactus-mine-project/overview/
Report Date: 2025
Region:
Project Status: Development
Commodity: Copper
Throughput: 28,000,000 t/y
Mine Life: 20 years
Mine Type: Open Pit
Ore type:
Cactus Mine Project — 2024 Technical Report
Cactus Mine Project — 2024 Technical Report
| Company | ASCU |
| Date | 2024-03-28 |
| Region | Casa Grande, AZ |
| Commodities | Copper |
| Mine Type | Open Pit, Underground |
| Throughput | 7,870 stph (Crushing Design) |
| Mine Life | 21 years |
| Annual Production | 30,000 t/y (Initial), 60,000 t/y (Expanded) |
| Status | Development |
Executive Summary
The Cactus Mine Project is a copper development initiative located in Casa Grande, Arizona, utilizing a combination of existing stockpiles, open pit mining (Cactus West), and underground resources (Cactus East and Park Salyer). The project is currently in the pre-feasibility study stage as of March 2024. The ore sources include oxide and lower-grade sulphide materials, which are suitable for treatment via a heap leach, solvent extraction, and electrowinning (SX/EW) process to produce LME Grade A copper cathodes.
The proposed processing facility is designed for modular, relocatable equipment supplied by Metalex Technologies to minimize capital costs. The initial production capacity targets 30,000 tons per year of copper cathodes, with an expansion planned for Year 3 to double capacity to 60,000 tons per year. The process involves crushing ore to 3/4-inch, agglomeration, and heap leaching with dilute sulfuric acid, followed by solvent extraction and electrowinning. The project anticipates a mine life of approximately 21 years based on the production plan.
Operational metrics indicate a design throughput capable of handling significant tonnage, with acid consumption managed through regeneration in the SX/EW circuit. The project leverages existing infrastructure assets from the Trekkopje project in Namibia for crushing and conveying, aiming to reduce installation time and costs. Water and power requirements are estimated at 1,867 gpm and 25 MW respectively, with a focus on efficient reagent usage and recovery rates of approximately 76% over the life of mine.
Operational Details
Processing Profile
Reports
Website: https://arizonasonoran.com/projects/cactus-mine-project/overview/
Report Date: 2024-03-28
Region: Casa Grande, AZ
Project Status: Development
Commodity: Copper
Throughput: 7,870 stph (Crushing Design)
Mine Life: 21 years
Mine Type: Open Pit, Underground
Ore type:
Cactus Project — Preliminary Economic Assessment (NI 43-101)
Cactus Project — Preliminary Economic Assessment (NI 43-101)
| Company | Arizona Sonoran Copper Company, Inc. |
| Date | 2023 |
| Region | Arizona, USA |
| Commodities | Copper |
Executive Summary
This Preliminary Economic Assessment (PEA) outlines the potential resources and processing methods for the Cactus Project in Arizona, USA. The project involves the development of an existing open pit mine with an expansion into a new underground mine extension to extract deeper resources. The processing strategy focuses on a conventional run of mine heap leach combined with Solvent Extraction and Electrowinning (SX/EW) to produce LME Grade A copper cathodes.
The ore body consists of oxide and sulfide enriched material. Oxide resources are processed on lined leach pads using sulfuric acid leaching, while enriched materials utilize bio-leaching technology. The initial plant design is modular, capable of producing 22,000 tonnes per annum (tpa) of copper cathodes, with expansion potential to 35,000 tpa. The mine life is estimated at 19 years, with a total mining rate of approximately 178.6 million tonnes per year.
Website: https://arizonasonoran.com/projects/cactus-mine-project/overview/
Report Date: 2023
Region: Arizona, USA
Project Status:
Commodity: Copper
Throughput:
Mine Life:
Mine Type:
Ore type:
