Pinto Valley is currently the only operating mill located in the historic Globe-Miami mining district of Arizona, one of the oldest and most productive mining districts in the US. Since its first recorded production in 1975, Pinto Valley has produced more than 4 billion pounds of copper, including 0.5 billion pounds of copper cathode.
and copper cathode,
*aims to maximize conversion of Mineral Resources to Mineral Reserves
Pinto Valley is an open-pit mine located at the west end of the historic Globe-Miami mining district of central Arizona, one of the oldest and most productive districts in the US, approximately 80 miles east of Phoenix via Highway 60. Several mines and numerous prospects have been developed in the area. Larger mines in the district are porphyry copper deposits associated with Paleocene granodiorite to Granite Porphyry stocks.
Pinto Valley has been in operation since 1972 and has produced more than four billion pounds of copper since then. Capstone acquired it from BHP in October 2013. The operation consists of an open-pit mine, a 60,000 tonnes per day (“tpd”) concentrator plant and a 25,000 tpd SX-EW plant. Pinto Valley is currently the only operating mill and the second-largest employer in the Globe-Miami district, supporting ~2,250 direct and secondary jobs each year.
The mine uses conventional open-pit hard rock mining methods (drilling, blasting, loading and hauling) to move copper-bearing sulphide ore to the primary crusher. The processing plant is a conventional porphyry copper concentrator that produces a primary copper sulphide concentrate and a by-product molybdenum concentrate. The plant flowsheet is typical of its era with primary through tertiary crushing, ball milling and conventional flotation. The mill has undergone several optimizations during its life. The most recent upgrade, the $31 million PV3 Optimization, was completed in 2021 and focused on innovation and a series of low-capital, quick payback projects to debottleneck operational performance. This included investments in the fine crushing plant and two new ball mill shells, as well as upgrades to the tailings thickeners and tailings pumping stations. The project improved productivity and increased recoveries and mill throughput to approximately 60,000 tpd during peaks.
The mine received a new US Forest Service Mine Plan of Operations in November 2021 and is fully permitted to operate for the duration of the current life of mine plan, which extends to 2039.
Growth – Pinto Valley 4 Study
The PV4 Study is expected in H1 2023 and is evaluating the mine’s long-term growth potential of existing mineral. Measured and Indicated Mineral Resources (inclusive of Mineral Reserves) of over 1.36 billion tonnes at 0.30% copper. The study includes a series of technological innovations including:
- Expansion of the use of Jetti Catalytic Leach Technology which has the potential to increase mill cut-off grades and increase tonnage available for leaching. Column leach testing is ongoing through 2022 and results will be included in the PV4 Study.
- Pyrite Agglomeration would have strong positive environmental, social and governance (“ESG”) implications as it would divert acid-generating minerals including pyrite and chalcopyrite from tailings to the dump leach operation. Additional copper recovery and lower costs via self–generation of free acid would also be key economic drivers for this project. Based on preliminary study results, the project is expected to require a low capex with a short payback period.
Higher mill throughput will be considered targeting up to 65,000-70,000 tpd. Key areas of investment include upgrades to ball mill motors, grinding circuit cyclones, and to the rougher flotation circuit and evaluation of coarse particle flotation. A low capital strategy is currently under review to improve coarse particle recovery with some modest investment in the current conventional flotation circuit. An expanded dump leach strategy would translate to higher grades sent to the mill for processing and increased copper cathode production by expanding dump leach tonnage.
Pinto Valley is also evaluating other new technologies such as Autonomous Trucking.
Geology and exploration
Pinto Valley is a copper porphyry deposit. The primary host rock is the Precambrian-age Lost Gulch Quartz Monzonite (equivalent to the Oracle Granite or Ruin Granite). The deposit’s economic mineralization is a hypogene ore body with chalcopyrite, pyrite, and minor molybdenite as the only significant primary sulfide minerals.
Copper Cities (BHP Copper Inc.) – The Globe-Miami mining district is host to several deposits and past-producing mining operations. In 2022 Capstone completed a two-phase exploration program under an 18-month access agreement to conduct drill and metallurgical test work at BHP Copper Inc’s Copper Cities project, located approximately 10 km east of the Pinto Valley Mine.
Phase I, comprised approximately 5,500 meters in 19 twin holes and was completed in April 2022. Phase II, comprising approximately 3,514 meters in eight geology model confirmation holes, was completed in May 2022. Assaying and metallurgical studies are underway pointing to a Mineral Resource estimate in 2023. To date, the Company has spent approximately $4.3 million USD of the $6.7 million USD programmed.
April 1 – December 31, 2022 Guidance
|Cu Production||41.0 – 45.0 thousand tonnes|
|C1 Cash Costs*||$2.45 – $2.60/lb Cu|
|Sustaining Capital||$55 million|
|Expansionary Capital||$15 million|
*Key Assumptions: Sulphuric Acid $280/tonne, WTI oil $100/barrel. All figures in USD.
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