The deposits of interest in this Technical Report are classified as VMS (volcanogenic massive sulphides). VMS deposits are an important source of copper, zinc, lead, gold and silver (Cu, Zn, Pb. Au and Ag) and form at or near the seafloor where circulating hydrothermal fluids driven by magmatic heat that have quenched through mixing with bottom waters or porewaters in near-seafloor lithologies. Massive sulfide lenses vary widely in shape and size and may be podlike or sheetlike. The location of VMS deposits is often controlled by synvolcanic faults and fissures, which permit a focused discharge of hydrothermal fluids. Massive sulphide ore in VMS deposits consists of usually more than 40 percent sulfides, dominated by pyrite, pyrrhotite, chalcopyrite, sphalerite, and galena. Non-sulfide gangue typically consists of quartz, barite, anhydrite, iron (Fe) oxides, chlorite, sericite, talc, and their metamorphosed equivalents. Sulphide ore composition may vary from Pb-Zn- to Cu-Zn-, or Pb-Cu-Zn-dominated, and some deposits are zoned vertically and laterally. VMS deposits have stringer or feeder zones beneath the massive zone that consist of crosscutting veins and veinlets of sulfides in a matrix of pervasively altered host rock.

Lalor Mine and 1901 Deposit
The mineralized envelopes are shallow dipping, with zinc mineralization defined to date beginning at approximately 600 m from surface and extending to a depth of approximately 1,100 m. The mineralization trends about N320° to N340° azimuth and dips between 30° and 45° to the north. It has a lateral extent of about 1,400 m in the north-south direction and 800 m in the east-west direction. Sulphide mineralization is dominated by pyrite and sphalerite. In the near solid (semi-massive) to solid (massive) sulphide sections, pyrite occurs as fine to coarse grained crystals ranging one to six millimetres and averages two to three millimetres in size. Sphalerite occurs interstitial to the pyrite.

The footwall gold mineralization is typical of any VMS footwall feeder zone with copper-rich, disseminated and vein style mineralization overlain by a massive, zinc-rich lens. The fact that the footwall zone is strongly enriched in gold suggests a copper-gold association which is comparable to other gold enriched VMS camps and deposits (Mercier-Langevin, 2009). Some of the footwall zones tend to be associated with silicification and the presence of gahnite.

General observations of the known gold zones indicate areas which are coarse-grained and porphyroblastic in nature are gold poor, while fine grain siliceous (± veins ± sulphide traces) and strained looking stratigraphy tend to be gold rich.

Watts Deposit
The Watts River deposit trends 020° azimuth and dips between 65° and 75° to the east. The sulphide intersections range from less than 0.3m up to 23m in core length, with a lateral extent of approximately 1,200m. Mineralization was intersected and interpreted as three lenses; Main Lens, Main Footwall Lens, and East Lens. The Main lens mineralization is comprised of coarse-grained pyrite, pyrrhotite, chalcopyrite, sphalerite, and minor galena. Mineralization was projected from the surface bedrock contact to a depth of 900m below surface as massive sulphides, fine disseminations and clots. The Main Lens has been divided into Main A, B, and C representing zones along the lens where appreciable copper and zinc grades and widths have been identified. The Main Footwall Lens lies in the immediate footwall of the Main Lens at depths of 600 to 880m below surface and tends to be slightly richer in sphalerite. The East Lens mineralization lies 400m into the hanging wall of the Main lens and extends from the surface bedrock contact to 280m below surface. Mineralization consists of narrow massive sulphides, disseminated, blobs, splashes, stringers of coarsegrained pyrite, pyrrhotite, chalcopyrite and lesser sphalerite. The massive sulphides exhibit a durchbeweget texture, characterized by the presence of rounded clasts of clear cherty quartz and amphibole inclusions within the sulphides. This texture suggests structural milling of the wall rock and the deposition of wall rock fragments within the recrystallized sulphides. The sulphides have generally been recrystallized to a coarse grain size, but sections of finer grained sulphides do occur.

Pen II Deposit
The Pen II deposit comprises a stratabound, semi-massive to massive sulphide lens with an adjacent stringer/disseminated sulphide zone. Mineralization is characterized by disseminated to massive, recrystallized and medium to coarse-grained sphalerite, pyrite, pyrrhotite and minor chalcopyrite. Based on the drilling completed by Hudbay and Callinan Mines Ltd. the mineralization extends from surface to 500 m below surface. The current strike length of the deposit is 400 m with an average thickness of 4 m. The deposit is conformable to stratigraphy, trends to the northeast at a N40º azimuth, a 45-65º dip towards the northwest.

Wim Deposit
The Wim deposit comprises a stratabound, semi-massive to massive sulphide lens with an adjacent stringer/disseminated sulphide zone. Mineralization is characterized by disseminated to massive, recrystallized and medium to coarse grained pyrite, pyrrhotite, chalcopyrite and minor sphalerite. Based on the drilling completed by Murgor, the VMS mineralization extends from surface to 720 m below surface. The current strike length of the deposit is 725 m with an average thickness of 10 m. The Wim deposit is conformable to stratigraphy, trends to the northwest at a N310º azimuth, a 40-45º dip towards the northeast and a plunge of 40º to the north. In addition, disseminated and stringer sulphides occur in the stratigraphic footwall of the Wim sulphide lens and may represent the feeder zone of the stratabound sulphide lens.

SNOW LAKE GOLD PROPERTIES
The Snow Lake Gold Properties (NBM, No. 3 Zone, Boundary Zone, Birch Zone and Squall Lake Area) are considered to belong to the quartz-carbonate vein gold subtype of orogenic lode gold deposits. This subtype of gold deposits consists of simple to complex quartz carbonate vein systems associated with brittle-ductile rock behaviour, corresponding to intermediate depths within the crust, and compressive tectonic settings.

At the regional scale, the quartz-carbonate vein gold deposits occur in two contrasting geological environments: deformed clastic sedimentary terranes and deformed volcano-plutonic terranes containing diverse volcanic assemblages of island-arc and oceanic affinities. Quartz-carbonate vein gold deposits in these environments tend to occur in clusters, or districts.

At the New Britannia mine the mineralization is associated with shear zones, faults, and simple to complex vein systems. The mylonitic zones (quartz-carbonate-mica) are predominantly less than 0.3 m thick but can thicken locally to between 3 m to 6 m. The gold bearing quartz-carbonate rocks are almost always situated next to or astride the fault.

Mineralization in No. 3 Zone, Boundary and Birch Zones is hosted within sheared biotite-quartz and carbonate altered volcanic and volcaniclastic rocks that host quartz-albite-iron carbonate veins with fine to coarse gold, and is associated with acicular arsenopyrite within the veins, wallrock and wallrock fragments.

In the Squall Lake area the gold-arsenopyrite mineralization is directly associated with tabular quartz veins that are rimmed by fine-grained arsenopyrite, sub-parallel to the enclosing stratigraphy, or as tightly folded with a near vertical attitude.

The two mining methods used at Lalor mine, 1901 deposit and the Snow Lake satellite deposits are variations of cut and fill mining or longhole open stope mining. In general, where the dip exceeds 35° and the orebody is of sufficient thickness, longhole open stope mining is preferred, whereas cut and fill mining methods are used in narrower, flatter areas. At Lalor, longhole mining represents 87% of total stope mining, and stope mining accounts for 92% of all mining, with development accounting for the other 8%.

Single pass overhand mechanized cut and fill mining is the preferred method where the ore is flatter than 35° and horizontal widths are less than 10m. The ore is accessed from a footwall drift by a crosscut developed at approximately -15%. Ore is mined in 5m high horizontal cuts. Unconsolidated backfill is placed tight to the back and the entrance crosscut is then back slashed to provide access to the next cut. Where ore widths are greater than 14m wide, mining is conducted by overhand post pillar cut and fill. Post pillars provide ground support to allow for selective mining of wide stopes. Backfill is placed to within 1.8m of the back and the entrance crosscut is back slashed to provide access to the next cut. Drifts and crosscuts in stopes are typically 7m wide x 5m high, with 7m x 7m post pillars. Mining retreats towards the access to reduce risks associated with poor ground conditions.

Benefits of longhole mining over cut and fill methods include reducing exposure to risk as a non-entry method and higher productivity/lower cost than cut and fill methods. The minimum design height of a longhole stope is 17m. In shallower dipping areas of the ore the interval is typically 17 to 20m, and in steeper dipping areas the interval is 20 to 25m. Stope widths assume a minimum mining width of 5m. A 5m rib pillar is added when unconsolidated rock is used as backfill.

Lalor
The hanging wall and footwall rocks at Lalor are generally of good quality, allowing the use of mechanized drilling and blasting techniques. The mineralized lenses dip at an average of 30°, but locally varying from sub-horizontal to 55°. Mining methods currently in use include cut and fill and longhole open stope. Paste backfill is used to increase recovery and accelerate the mining cycle. Low grade areas will be filled with rock from waste development.

Ramps are typically mined at up to +/- 15% grade to provide access between levels. Rounds are 4m long and typical dimensions are 6m wide by 5m high.

At Lalor, main ventilation raises and ore pass raises are developed by a mining contractor using a raisebore and/or Alimak climber. Ground support and ladder ways are installed as required. Longhole slot raises, transfer ore passes, and auxiliary ventilation raises are limited to approximately 35m long and are developed using longhole conventional drop raise techniques. Drain, paste backfill and electrical cable holes are drilled using longhole or raisebore drills and are reamed to designed diameter. Backfill is either unconsolidated waste rock backfill (URF) or consolidated paste backfill.

Lalor Mine uses Epiroc’s Autonomous Mucking System which includes an operator’s station on surface allowing control of up to three LHD’s concurrently.

1901
For 1901, two mining methods will be used. The primary method will be Post-Pillar Mechanized Cut and Fill (PPMCAF) used where the resource has sufficient vertical thickness to mine multiple consecutive cuts. Where there is limited vertical thickness and the resource can be mined in a single cut, Inclined Room and Pillar will be used. The PPMCAF stopes will be backfilled with unconsolidated waste rock.

For 1901, access has been started from the existing Lalor ramp and will approach the deposit from the hangingwall side. The main development profile will be 5 m wide x 5 m high, with dimensions established to allow for the required ventilation flow velocity as well as to meet other criteria like minimum equipment clearances. All ramp and lateral excavations will be developed using traditional drill and blast methods and diesel-powered mobile equipment.

Major vertical development will consist of an existing 3m diameter fresh air raise (FAR) as well as a planned 3.5m diameter return air raise (RAR) that is to be raisebored roughly 500m in length. Additional internal raises will be used for ventilation and egress and they are planned to be developed with an Alimak method.

At 1901, in areas that undulate and are typically narrower, an inclined room and pillar method will be used. This method does not require backfill, as there is only one cut per level.

WIM
At WIM and 3 Zone, longhole retreat mining methods were selected to excavate the orebodies. Utilizing this method will require a bottom-up mining sequence with mining fronts progressing in from the orebody extents towards the center of the orebody.

At WIM and 3 Zone, all lateral ore and waste development is designed to accommodate Sandvik LH514 and LH517 LHDs and Sandvik TH550 trucks (or equipment of equivalent size). Levels generally consist of sills in the ore with level access off the main ramp to the sill.

The requirements for vertical mine development at WIM and 3 Zone include FARs and secondary egresses. The main ventilation raises are sized based on ventilation requirements and will also be used as a second means of egress. It is envisioned that the raises will be developed using an Alimak method and slashed to the appropriate dimensions as the raise is supported and manway installed.

At WIM and 3 Zone, URF backfill material will come from underground development. The waste produced before stoping begins will be stockpiled on surface and hauled underground as required to replace removed ore. Once stoping begins, waste will be stockpiled underground for use as fill.

STALL MILL
Crushing Coarse ore from the mine is transported to a primary crushing plant located at the Chisel mine site and is operated by a third-party contractor. The product from the crushing plant is then trucked to the Stall mill and placed in coarse ore bins or a stockpile. Material from the bins is reclaimed via vibrating feeders and conveyed into a Hewitt Robins 762mm x 1220mm jaw crusher. The discharge is combined with that of the secondary Symons Standard cone crusher to feed a Tyroc 2.4m x 6.1m double deck vibrating screen. The undersize from the bottom deck is conveyed to the fine ore bins (FOB) while the oversize of the two decks is combined to feed the Symons cone crusher and then recirculated to the screen deck in a closed loop.

The described crushing circuit is in the process of being decommissioned and replaced with an external crushing circuit to service both the Stall and New Britannia mills. The new external crushing circuit start-up is aligned with the New Britannia mill commissioning schedule.

Grinding
From the fine ore bins, crushed ore is conveyed to the two independent Stall and Chisel circuits. The Stall circuit, which processes approximately two thirds of the mill feed, includes a 3.2m diameter x 4.9m rod mill and a 3.8m diameter x 5.5m ball mill. The Chisel circuit has a 2.1m diameter x 3.0m rod mill and a 3.2m diameter x 4.0m ball mill.

Each rod mill discharges into a dedicated hydrocyclone feed pump box where it is combined with the ball mill discharge and with dilution water. Each hydrocyclone underflow returns to their respective ball mill. The hydrocyclone overflow from each circuit combines and discharges into the hydrocyclone overflow pump box. The product reports to a flotation feed pump box through a trash screen. Lime is added to each rod mill to control the pH in the flotation feed.


NEW BRITANNIA MILL
Grinding
The crushed material is reclaimed from the FOB via conveyors into the rod mill and then discharged into a hydrocyclone feed pump box, where it is combined with the ball mill discharge and dilution water. A variable speed hydrocyclone feed pump feeds a the hydrocyclones cluster. The hydrocyclone underflow returns to the ball mill while the overflow flows via gravity to a trash screen and then is pumped to the flotation circuit.

PROPERTY DESCRIPTION
Hudbay operates two concentrators in the Snow Lake / Flin Flon area: the Stall mill located approximately 16 km from Lalor and the Flin Flon mill located 200 km to the west. While the Flin Flon mill provides an opportunity to truck additional production from Lalor that the Stall mill cannot accommodate, the recent operating performance of the Stall mill through 2020 has resulted in minimum tonnage being trucked to Flin Flon from Snow Lake over the past year as the Stall mill has been operating close to the 3,900tpd produced by Lalor mine.

Hudbay also operates a zinc metallurgical plant in Flin Flon with a capacity of 115,000 tonnes per annum of refined zinc. However, Hudbay intends to cease operations and put the zinc plant and the Flin Flon mill on care and maintenance at the end of Q2 2022, when Hudbay’s 777 mine closes. After the zinc plant closure, the concentrates produced from the Stall and Flin Flon mills will be sold to market.
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