Lalor and Snow Lake Operations — 2021 Technical Report

This technical report describes the mineral processing and metallurgical testing approaches for the Lalor mine and associated Snow Lake satellite deposits, with ore processed at the Stall and New Britannia concentrators.

Report context

This Form 43-101F1 Technical Report, dated 2021, covers the Lalor Mine and nearby Snow Lake satellite deposits in Manitoba, Canada. The report presents a mine plan that contemplates 5,300 tonnes per day of base metal, gold and copper-gold ore feed to the Stall and New Britannia concentrators, with the New Britannia mill under refurbishment and planned start-up in spring 2021.

Processing route

Existing processing infrastructure

Hudbay operates two ore concentrators: the Stall mill located approximately 16 km from Lalor and the Flin Flon mill located in Flin Flon. The Stall mill is currently operating seven days per week, producing at or above 3,800 tpd. The Stall mill has two circuits with design capacities of 900 tpd and 2,180 tpd.

Both concentrators have two flotation circuits producing a zinc concentrate and a copper concentrate. The zinc concentrate produced at Stall is hauled by truck to Hudbay metallurgical facilities in Flin Flon. The copper concentrates are sold to market. The tailings from the Stall mill are deposited in the Anderson Tailings Impoundment Area or used at the paste plant.

During the 2021-2022 period, although 100% of Lalor's production will be processed at the Stall or New Britannia mills, any additional production could be trucked to the Flin Flon mill until this facility shuts down at the same time as the zinc plant closes.

New Britannia mill

The New Britannia mill is located approximately 16 km north of the Lalor mine and was under construction (refurbishment) with a planned start-up of operations in the spring of 2021. Historical production at the New Britannia mill saw throughput rates of up to 2,000 tpd based on the availability of ore from the underground operation. The mill infrastructure consists mainly of three buildings and houses the crusher and mill/gold circuits. There are two existing crusher buildings: primary and secondary. The primary building houses the jaw crusher, and the secondary building houses the cone crusher and screen deck, each building with associated conveyors. The existing mill building contains the grinding and gold circuits, elution, EW and refining. The outside equipment includes thickener and leach tanks.

Proposed processing configuration

Once the New Britannia mill becomes fully operational in the second half of 2021, the mine plan will target a production of 1,500 tonnes per day of gold ore, supplemented by 3,800 tonnes per day of base metal ore. The total production rate of Lalor is maintained at 5,300 t/d from the second half of 2022 until 2026.

The strategy for the 2021 mine plan at Lalor is to mine base metals of higher grade zinc while at the same time advancing the development required to start mining the gold and copper gold zones.

Stall mill configuration

The Stall mill processes base metal ore from Lalor. A traditional sequential Cu-Pb-Zn flotation circuit is used at Stall. Several metallurgical projects are being advanced to match the configuration of the mill to the requirement of the ore, including addressing the increasing Pb:Cu ratio, increasing gold recovery at Stall, and improving flotation recoveries through reduction of the feed size.

Paste plant

The Lalor paste plant was commissioned in the third quarter of 2018, is located northeast of the existing head frame complex, and is capable of delivering 165 tph solids (tails) or 93 m³/hr of paste. The paste plant is capable of varying the binder content in the paste to provide flexibility in the strength gained from the paste where higher and early strength may be required depending on mining method.

Tails are currently pumped from the Stall concentrator to the Anderson TIA and diverted, as needed, to the Anderson booster station. Two pipelines are installed between the Anderson booster pump station and the paste plant located at Lalor mine site, which are situated approximately 13 km apart.

Proposed upgrades

With the increase in the mineral reserves of the Lalor gold zones alongside additional satellite deposits, an opportunity exists to increase the throughput rate in the future. The study to date has identified that the tailings pipeline, pre-leach thickener and various minor pumping systems would require upgrade to accommodate the increased tonnage rate. In addition to the processing equipment upgrades, the study includes the upgrade of the pipeline corridor road to accommodate ore haulage from Stall to New Britannia to remove traffic from the public access road.

Metallurgical testwork

Several metallurgical projects are being advanced, including: confirming the amenability of the 1901 gold lenses to processing at the New Britannia mill, increasing gold recovery at Stall, and improving flotation recoveries through reduction of the feed size.

For the WIM deposit, seven metallurgical holes were completed for a total of 2,533 metres in 2019. Mineralization from these holes was sent off for metallurgical testwork. Results have confirmed that the mineralization at Wim could attain processing recoveries in copper, silver and gold similar to the ones estimated for the Lalor copper-gold zones.

For the 1901 deposit, in 2020 Hudbay completed a pre-feasibility study on the engineering and mineral processing of the 1901 measured and indicated mineral resources.

Processing satellite deposits

The 1901 deposit would be accessed by lateral development from the ramp and would use the existing surface infrastructures. The Pen II deposit, WIM deposit, and Watts deposit are within trucking distance to either Stall or New Britannia mill. The Watts deposit located within 200 km of the Snow Lake processing facilities offers additional opportunities to maximise the use of the Stall and New Britannia mills and/or extend their operating life.

Future operations timeline

While the Stall mill closes in 2031 based on mineral reserve estimates only, the New Britannia mill remains in operation for an additional six years until 2038 supported by the WIM and 3 zone mining production.

Key reported parameters

Technical qualifications

The author considers that the mineral resources and reserves as classified and reported comply with all disclosure in accordance with requirements and CIM Definitions. The author is not aware of any mining, metallurgical, infrastructure, permitting or other relevant factors that could materially affect the mineral reserve estimate.

Standard professional procedures were followed when preparing the contents of this Technical Report. Data used in this Technical Report has been verified where possible and the QP has no reason to believe that the data was not collected in a professional manner and no information has been withheld that would affect the conclusions made herein.

The information, conclusions, opinions, and estimates contained herein are based on: information available to Hudbay at the time of preparation of this Technical Report, and assumptions, conditions, and qualifications as set forth in this Technical Report.

All the relevant capital and operating expenditures required to execute the life of mine plan of the Snow Lake operations have been accounted for in the demonstration of economic viability of the mineral reserve estimates including growth and sustaining capital costs and operating costs for the mining, milling and refining activities as well as the attributable general and administrative costs.

Source: Lalor and Snow Lake Operations, Manitoba, Canada, Form 43-101F1 Technical Report, Section 17 – Recovery Methods, and relevant processing sections.