The Minorca deposits are examples of Superior-type BIF deposits, specifically the Biwabik Iron Formation (Biwabik IF), which is interpreted to have been deposited in a shallow, tidal marine setting and is characterized as having four main members (from bottom to top): Lower Cherty, Lower Slaty, Upper Cherty, and Upper Slaty. Cherty units generally have a sandy granular texture, are thickly bedded, and are composed of silica and iron oxide minerals. Slaty units are fine grained, thinly bedded, and comprised of iron silicates and iron carbonates, with local chert beds, and they are typically uneconomic. The mineral of economic interest at Minorca is magnetite.

The Biwabik IF at Minorca consists primarily of carbonates, iron silicates, fine-grained quartz, and iron oxides. These layers are visually distinct, locally separated into slaty beds and cherty beds. The ratio of slaty to cherty beds and distance between these beds are key indicators used during logging, as well as bedding style, texture, color, and magnetic strength. Slaty beds are dark gray in nature, consisting primarily of magnetite in mineralized zones, and range from one millimeter (0.04 in.) to upwards of two centimeters (0.78 in.) in thickness. Cherty beds range from gray to green in color depending on the ratio of fine-grained quartz (gray color) to iron silicates (green color). These beds vary in thickness to upwards of 10 cm (3.9 in.) and may or may not contain disseminated magnetite. Carbonates typically occur as granular, recrystallized grains of varying size and commonly occur in late-stage, quartz-carbonate-filled fractures, which run variably (orientation, length, width, continuity) throughout the iron formation. The Upper Slaty and Lower Slaty members are visually distinctive as they are dominated by slaty beds; however, these beds rarely contain any notable iron oxide content.

The Lower Cherty and Upper Cherty members of the Biwabik IF host the economic mineralization at Minorca. These members are subdivided into LC1-LC5B and UC1-UC3. Waste rock units (Lower Slaty and Upper Slaty members) cap the Lower Cherty and Upper Cherty members and are distinctively fissile and weakly magnetic as compared to the ore-bearing units.

Glacial Till (OVB): The iron formation is overlain by mostly clayey, reddish-brown glacial till. Thickness in the mining areas varies from 0 ft to 100 ft with an average depth to bedrock of 24 ft.
Upper Slaty (US): The Upper Slaty is weathered and thinly bedded. Average thickness is less than 20 ft where it has been intersected by diamond drilling (19.7 ft).
Upper Cherty (UC): The Upper Cherty zone is generally gray or dark gray to black in color. It is usually a thinly bedded zone interbedded with green, thicker-bedded, cherty intervals containing a high-angle quartz vein. It has an average thickness of 250 ft. In the East Pit deposit area, this subunit is lean to non-magnetic, with very little of the material meeting ore grade thresholds. Unit Text = UC, Code=6 (note: this code is applied in the East model where the Upper Cherty has not been divided). In the Laurentian Pit, the Upper Cherty member is split into three subunits: UC3, UC2, and UC1 from top to bottom.
Upper Cherty 3 (UC3): East of section 7000, in the Laurentian Pit, the UC3 is gray in color, massive, and has a salt-and-pepper to blotchy texture with disseminated magnetite. West of section 7000, it has a reddish color; it is still massive but leaner and less magnetic. Average thickness is 170 ft.
Upper Cherty 2 (UC2): The UC2 is reddish in color, bedded, with scattered white bands of quartz and carbonates and buff- to green-colored silicates. Average thickness is 50 ft.
Upper Cherty 1 (UC1): The UC1 is pinkish-gray in color. It is bedded to massive and contains an abundance of pink carbonates. Average thickness is 30 ft.
Lower Slaty (LS): The Lower Slaty member averages 130 ft in thickness. It is black to green in color, laminated to thinly bedded, and nodular in places.
Lower Cherty 5B (LC5B): Greenish-gray in color, with thin-bedded bands alternating with thick, chert-rich bands. Average thickness is 15 ft.
Lower Cherty 5A (LC5A): Gray in color with a bedded to mottled texture in places. The top of the subunit is rich in pink carbonates. Average thickness is 60 ft.
Lower Cherty 4 (LC4): The LC4 is brownish-gray in color, with wispy bands of magnetite. It has some disseminated magnetite in the chert bands. It contains ovate clasts of carbonate and silicates rimmed with magnetite. Average thickness is 65 ft.
Lower Cherty 3 (LC3): Pinkish- to reddish-gray color, blotchy texture, primary hematite, green silicates, and straight bedding.
Lower Cherty 2 (LC2): Reddish-gray color with green silicate bands, primary hematite.
Lower Cherty 1 (LC1): Reddish-gray color, basal.
Quartzite (QTZ): Green color, conglomeratic at top, and chloritic.

The mineral targeted at Minorca is magnetite, bound in rock regionally referred to as taconite. The recoverable magnetic iron in ore ranges from 16% to 30%. Quartz, carbonates, and iron silicates are the common gangue minerals. The deposit is layered and consistent. The Mine targets taconite of the Upper Cherty and Lower Cherty members in its Laurentian Pit. The Upper Cherty ore is higher in concentrate silica and more difficult to process. It needs to be blended with lower concentrate silica ore to make it economic. In the East Pit, only the Lower Cherty ore is processed; the Upper Cherty lithologic subunits do not contain enough magnetic iron in this area.

Common carbonates include ankerite and siderite, which carry a definitive milky white to slightly red appearance. These carbonates occur variably throughout the iron formation and are most apparent at the base of the LC5A subunit and in the UC1 and UC3 subunits. Kutnohorite is present, but requires Scanning Electron Microscopy (SEM) or X-ray diffraction (XRD) to separate it from ankerite. Iron silicates are visibly distinguishable from carbonates, quartz, and iron oxides; however, SEM or XRD is required to discern specific iron silicate minerals from each other. Talc, stilpnomelane, and minnesotaite are the common iron silicates present in the iron formation (Totenhagen et al., 2011).

In the East Pit area, the formation strikes west and dips to the south at approximately 8°. Ore-grade material is found primarily within the Lower Cherty member of the formation. The iron formation along the north edge of the deposit is overlain to the south by the Virginia Formation. At the Laurentian Pit, the formation strikes west and dips to the south at approximately 18°. Ore-grade material is found in both the Lower Cherty and Upper Cherty members of the formation.

The lithology units are typically similar between East 1 and East 2 pits of the East Pit and the Laurentian Pit, with the exception being the Upper Cherty member in the East model area. The difference lies primarily in the UC1 and UC2 units, which carry minor visual variations in bedding thickness and color while also containing more inconsistent MagFe grades. Due to this, the Upper Cherty member is currently undivided in the East model, where additional drilling is required to define ore/waste subunits in this member. The Upper Cherty member is primarily outside of the permitted limits of the East deposit.

The Central deposit appears similar to the East deposit based on exploratory drilling and subsequent logging in 2011, 2012, and 2018 as well as modeling in 2013 and 2019. The dip ranges from 10° to approximately 15° as this deposit lies between the Laurentian and East pits. Similar to the East Pit area, the Upper Cherty member in the Central deposit will require further definition through exploratory drilling, logging, and modeling to differentiate ore/waste subunits.

The Laurentian, East 1, and East 2 areas are mined using conventional surface mining methods. The surface operations include:
• Clearing and grubbing;
• Overburden (glacial till) removal;
• Drilling and blasting (excluding overburden);
• Loading and haulage.

The open-pit operation at Minorca has a mining rate of approximately 8.6 million long tons (MLT) of ore per year and produces 2.8 MLT of wet flux iron ore pellets.

The current LOM plan has mining for 14 years and mines the known Mineral Reserve. The average stripping ratio is 0.8 waste units to 1 crude ore unit (0.8 stripping ratio).

The final Laurentian Pit is approximately 1.2 mi long along strike, 0.9 mi wide, and up to 640 ft deep. Crude ore averages approximately 24.4% MagFe. The final East 1 Pit is approximately 0.9 mi along strike, 0.5 mi wide, and up to 310 ft deep. Crude ore within the East 1 Pit averages approximately 22.5% MagFe. The East 2 final pit is approximately 0.7 mi along strike, 0.4 mi wide, and up to 350 ft deep. The East 2 Pit crude ore contains an average of 23.7% MagFe.

Primary production for all mine pits includes drilling a combination of 12.25 in.- and 16.00 in.-diameter rotary blast holes. Production blast hole depth varies as the pit benches transition from the footwall contact to a full 35 ft bench height. Burden and spacing varies depending on the material being drilled. The holes are filled with explosive and blasted. A combination of front-end loaders (FEL) and hydraulic shovels load the broken material into a mixed fleet of 200 ton- and 240 ton-payload mining trucks for transport from the pit.

The Mine follows strict crude ore blending requirements to ensure that the Plant receives a uniform head grade. The two most important characteristics of the crude ore are magnetic iron content and predicted concentrate silica. Generally, two ore zones are mined at one time to obtain a satisfactory crude ore blend for the Plant. Crude ore is hauled to the crushing facility and either direct tipped to the primary crusher or stockpiled in an area adjacent to the primary crusher. The crude ore stockpiles are used as an additional source for blending and production efficiency.

The major pieces of pit equipment include diesel hydraulic shovels, FELs, haul trucks, drills, bulldozers, and graders. Extensive maintenance facilities are available at the mine site to service the mine equipment.

The Laurentian, East 1, and East 2 pits are relatively shallow and, structurally, the in situ crude ore and waste rock is of excellent quality. The deposit dips into the highwall at 8° to 10°, reducing the risk of large-scale slope failures.

Overburden and waste rock material is discretely stockpiled concurrently within designated stockpiles. Waste material removed from the Laurentian Pit can be placed either external or internal (in-pit) to the mine pit. In-pit waste material placement is the preferred method of storage, but the advancement of the Laurentian in-pit stockpile is limited to final pit footwall exposure along the bottom of the pit. When in-pit stockpiling capacity is unavailable, waste material is placed external to the pit in surrounding stockpiles located to the north and east. The East 1 and East 2 pits are not permitted for in-pit waste stockpiling. All waste material for these pits is placed externally in stockpiles located to the north of each respective mining pit.

Final wall slopes, effectively the IRA as there are no haul ramps in the final highwall, are at 49.4°. The final wall design uses a double bench configuration with a bench height (BH) of 35 ft, totaling 70 ft between each 40 ft CB.

Haulage ramps are also incorporated into the designs. The ramp width is sized at 150 ft, which can safely support two-way traffic of the 200 ton- and 240 ton-payload mining trucks.

The maximum pit depth and vertical highwall exposure is approximately 640 ft for the Laurentian Pit, and 310 ft and 350 ft for the East 1 and East 2 pits, respectively.

The basis of the production schedule is to:
• Consistently produce 2.8 MLT/y of wet flux pellets for the LOM.
• Limit crude ore delivery to crusher to 8.7 MLT/y.
• Limit yearly concentrate silica to a maximum of 4.2%. SLR notes that, in general, a target of 3.8% concentrate silica is ensured to reduce the use of the flotation circuit over the LOM.
• Limit the Upper Cherty (UC3, UC2, and UC1) component of the overall ore blend composition to a maximum of 30%.
• Limit total mined tons per year at approximately 18 MLT to balance both stripping requirements and mine equipment fleet utilization.

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The Minorca property has the capacity to produce approximately 2.8 MLT of wet flux iron ore pellets annually.

The concentrator comprises three lines with the following unit operations included in each of the three lines:
• Rod milling – open circuit;
• Cobber magnetic separation;
• Ball milling – closed circuit;
• Rougher magnetic separation;
• Cyclone classification;
• Cyclone overflow hydroseparation;
• Hydroseparator underflow screening;
• Finisher magnetic separation;
• Finisher magnetic concentrate thickening;
• Magnetic concentrate reverse flotation;
• Rougher flotation concentrate (underflow) to concentrate thickening;
• Rougher flotation tailings (overflow) magnetic separation;
• Rougher tailing magnetic separation concentrate regrinding;
• Scavenger reverse flotation;
• Scavenger concentrate to rougher flotation feed;
• Concentrate collection and storage;
• Concentr ........