The HibTac deposit is an example of Lake 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 predominantly composed of chert, magnetite, iron silicates (talc, stilpnomelane), and, in specific geologic units, carbonate (ankerite). Slaty units are fine grained, thinly bedded, and comprised of iron silicates and iron carbonate, with local chert beds, and they are typically uneconomic. The mineral targeted at HibTac is magnetite. Supergene weathering and oxidation has locally altered the primary assemblage to hematite, goethite, and chert, generally increasing in intensity with proximity to isolated occurrences of Cretaceous Coleraine Formation south of the mine and faults or fracture zones. Partial or complete oxidation of magnetite to hematite precludes recovery by magnetic separation, resulting in local degradation of potential ore intervals to waste rock. The Biwabik IF at HibTac 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 ........

The Hibbing Taconite Property (HibTac) is mined using conventional surface mining methods. The Mine requires large 200-plus ton mining trucks, and some areas of the pit require long hauls. The surface operations include:

• Clearing and grubbing;
• Overburden (glacial till) removal;
• Drilling and blasting (excluding overburden);
• Loading and haulage.

The Mineral Reserve is based on the ongoing annual average ore production of 21.9 MLT from the Group I, II, III, IV, and V pits, producing an average of 5.6 MLT/y of wet pellets for domestic consumption. The HibTac operations have no current expansion plans and are likely to cease operating once the reserves are depleted by 2026.

The current LOM plan has mining scheduled for five years and mines the known Mineral Reserve. The average stripping ratio is 1.0 waste units to 1.0 crude ore units (1.0 stripping ratio).

There are 20 mining pits/phases with varying dimensions, with a maximum depth of approximately 600 ft attained in two of the pits/phases.

Primary production for all mine pits includes drilling 16.00 in.-diameter rotary blast holes. Production blast hole depth to 40 ft bench heights is drilled. 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 electric shovels load the broken material into 240 ton-payload mining trucks for transport from t ........

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