The Northshore iron deposit is a classic example of the Lake Superior-type BIF deposit. Lake Superior-type BIFs occur worldwide and are exclusively Precambrian in age, deposited from approximately 2,400 Ma to 1,800 Ma.

Magnetite is the principal economic mineral at the Mine and occurs dominantly in thin to thick bands and layers, as medium- to coarse-grained disseminated grains, and as grain aggregates. Magnetic iron content ranges between 22% and 30% in the mineralized stratigraphic subunits within the deposit at the Mine. Local variation in silicate mineralogy and lithologic textures due to contact metamorphism presents unique challenges for grade control relative to deposits hosted in the western Biwabik IF. These changes affect many aspects of the operation including process metallurgy and hardness. Supergene oxidation of magnetite occurs locally along fracture planes but is generally uncommon.

Several geological structures are important at Northshore:
• The sharp contact between the Biwabik IF and the Duluth Complex identified and modeled from drilling data.
• A homocline in the BIF at the contact of the Duluth Complex, striking approximately east-northeast and dipping approximately 7° to the southeast.
• Several high-angle normal faults exhibiting variable displacement.

Emplacement of the Duluth Gabbro is responsible for the variable mineralogy observed at Northshore. Regional metamorphism related to this event locally aff ........

The Northshore deposit is mined using conventional surface mining methods. The surface operations include:
• Overburden (glacial till) removal;
• Drilling and blasting (excluding overburden);
• Loading and haulage;
• Crushing and rail loading.

The Mineral Reserve is based on the ongoing annual crude ore production of 16 million long tons (MLT) to 18 MLT producing a total of approximately 5.1 MLT of wet pellets for domestic consumption.

The current LOM plan has mining scheduled for 48 years and mines the known Mineral Reserve. The average strip ratio is approximately 0.8 waste units to 1 crude ore unit (0.8 strip ratio).

The final Northshore pit is a single pit approximately 10.5 mi along strike, up to 1.2 mi wide, and up to 420 ft deep.

The Mine’s operation has a strict crude ore blending requirement to ensure the Plant receives a uniform head grade. The most important blending characteristics of the crude ore are the MagFe, Conc_Fe, and ore hardness (i.e., Grindability). Generally, three crude ore loading points from different subunit groupings (i.e., the Intermediate, High Grade, Footwall Group, and Lower Cherty subunit groupings) are mined at one time to obtain the best 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. Haul trucks are alternated to blend delivery from the mul ........

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