Garson is a deformed Contact-style deposit. Contact-style mineralized zones are remobilized into a series of near-parallel ductile shear zones. Shear-hosted copper–nickel sulphides are offset by later stage dykes and possible late-stage shearing. The 1 Shear and 4 Shear are the primary mineralized zones.

The 1 Shear extends from surface to below 6500 Level, a distance of approximately 1,980 m. It has a strike length of 120–600 m, with strike length decreasing with depth. Hanging wall to footwall widths along the orebody vary between 3–60 m, with an average width of 10 m.

The 4 Shear extends from the 2800 Level to a currently known limit of 6700 Level, a distance of approximately 1,200 m. It has a strike extent of 685 m and an average width of 7 m. It strikes east– west and generally dips 70° south. The 4 Shear orebody runs parallel to the 1 Shear orebody, lying approximately 45 m to 60 m to the northwest.

Both shears dip at a slightly shallower angles than the SIC contact, which means that above the 4000 Level the shears are mostly hosted in the SIC with the dominant lithology being Sublayer Norite and below the 4000 Level the shears cut the metasedimentary and metavolcanic Huronian footwall rocks.

The deposit is crosscut by two separate olivine diabase dykes. These dykes are sub-parallel to each other and range in width from 15–60 m.

The Garson region was subjected to significantly more structural activity than the rest of the Sudbury Basin. This structural activity caused the Huronian footwall rocks to overturn and form the hanging wall. This overturning caused a significant amount of shearing sub-parallel to the strike of the Garson Contact-style deposits producing a series of near-parallel shears.

Major geological structures include the Garson Fault, the 2500 Shear, and the 3500 Shear. The 2500 shear and the 3500 structures and are roughly 12–23 m wide, strike north–northwest and dip steeply to the east. Fractures are commonly filled with calcite, galena, marcasite and sphalerite. Late-stage faults and fractures also deform the orebodies.

There are a number of “cross-over” sulphide zones that connect the 1 Shear and 4 Shear Orebodies. These cross-over zones are near vertical and <3 m wide.

The mineralization is dominated by inclusion massive sulphide and massive sulphide lenses and stringers, contorted schist inclusion sulphide, ragged disseminated and sulphide breccia. Pyrrhotite is the most common sulphide mineral. Pentlandite is the main nickel-bearing mineral. Chalcopyrite is the main copper-bearing mineral, and is locally associated with elevated precious metals. Trace to minor amounts of cobaltite–gersdorffite, niccolite (NiAs), nickeliferous pyrite, marcasite, sphalerite, galena and argentopentlandite (Ag(Fe, Ni)8S8) are distributed throughout the 4 Shear.

Platinum-group minerals include michenerite, hollingworthite, irarsite, froodite, Pd-melonite and sperrylite. The oxide mineral assemblage is composed of magnetite, with magnetite content varying from 0.5–2%. Rare and local clustering of lead and zinc mineralization occurs as veinlets associated with late fracture zones and within major structures. The hydrothermal alteration assemblage consists of marcasite (FeS2) and violarite (FeNi2S4).

Arsenic-bearing mineral assemblages occur primarily along the strongly sheared hanging wall and footwall-sulphide contacts. Arsenic also occurs within the main sulphide zones associated with latestage structural/schistose zones. Commonly, occurrences can be found associated with shear planes in the halo of the main mineral zone associated with low-grade disseminated and copper rich veinlets. The dominant As-bearing minerals are niccolite and cobaltite–gersdorffite. Maucherite (Ni11As8) has been reported but is relatively rare. Other arsenide and sulpharsenide minerals are present in trace amounts including sperrylite. Stockpiling and re-handling of high arsenic content ore is done to ensure processing requirements are achieved.

The Garson Mine is located immediately northeast of the town of Garson. Garson mine is a part of Vale integrated Ontario Operations which also includes (Coleman, Copper Cliff, Creighton and Totten mines), processing and refining facilities (Clarabelle Mill, Copper Cliff Smelter and Nickel Refinery, Port Colborne refining complex), supported by the Clydach Refinery in Wales, and non-operating mines, and non-producing properties.

The Garson deposit includes the actively mined Garson Surface Ramp (13 and 360), and Garson Mine #1 Shear, #4 Shear deposits. Inactive deposits include the McConnell, and Garson Ramp (600) zones.

The Garson Main Mine is accessed via the 1,293 m (4,240 ft) deep Garson #2 Shaft while the Surface Ramp is accessed through a portal from surface, situated about 400 m west of the shaft collar. The main Level accesses from #2 Shaft are 3800 and 4000. The secondary means of egress for the Main Mine is through is a ladder system in the power raise from surface to 3400 Level. Access. Primary and secondary egresses from the bottom of the Main Mine on 5200 Level to 3400 Level are a combination of haulage declines and relatively short ladderway systems.

The Garson Main Mine and Garson Surface Ramp operations are physically connected on the 200, 400 and 600 Levels. The 200 Level has an escapeway to surface and serves as a secondary means of egress for the Surface Ramp operation. On the 400 Level of the Surface Ramp, access to the Main Mine is via the 400 Level Track Drift. The 400 Level has a escapeway to the 200 Level. This level also serves as a secondary means of egress for the Surface Ramp. A third location as secondary means of egress between the Surface Ramp and the Main Mine is 660L and 790L escapeway drift. The 790 Escapeway drift is accessed from the 660 Level access drift on the Surface Ramp side and connects to the 600 Level main sill drift on the Main Mine side.

Slot–slash and Uppers retreat mining methods are employed for ore extraction.

Ore and waste rock is mucked using LHDs to re-muck storages on each level and loaded into 45 t or 27 t diesel trucks. Ore is hauled up the ramp and dumped into a storage bin from where it is loaded through a chute into rail cars. The ore is then trammed by rail along the 4,000 Level and into another chute feeding a crusher. Crushed ore is hoisted to surface via No. 2 Shaft in 10 t skips that have a capacity of 231 t/hr.

The majority of waste rock is used underground as fill, though some hoisting of rock does take place. Waste rock is loaded into 45 t diesel trucks by LHD and hauled up the ramp for hoisting to surface through the #2 Shaft in 9 t (10 ton) skips or disposed as fill into nearby open stopes.

The Garson Ramp mining zone hauls ore and waste from underground in 36 t (40 ton) trucks via ramp to surface for shipment to the mill or disposal. Production capacity is approximately 454 t/day.

Alluvial sands are used for backfilling. High-density (paste) backfill is used at the Main zone of the Garson Mine.

Ventilation System consist of One major fresh air system; four return air systems and has 1,050 kcfm capacity.

The area below shaft bottom (4,000 Level) is dewatered by a series of intermediate sumps and pumping stations located on the 4,270, 4,600, 4,900 and 5,100 Levels. These pumps feed the main pump station located on the 4,000 Level at the shaft. Waste water is pumped from the 4,000 Level to the 3,000
and 1,000 Levels, and ultimately to surface. Approximately 750–1,000 k gallons of water are pumped out daily. Water is treated before being released into the environment.