United States

Northshore (Peter Mitchell) Mine

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Categories

Overview

Mine TypeOpen Pit
Commodities
  • Iron Ore
Mining Method
  • Truck & Shovel / Loader
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ShapshotNorthshore operation is a part of Cleveland-Cliffs 'Steelmaking segment' Operation.

The Northshore operation includes an open pit truck and shovel mine where two stages of crushing occur before the ore is transported along a wholly owned 47-mile rail line to the plant site in Silver Bay. The concentrator produces magnetite concentrate, which is delivered to the pellet plant located on-site. The plant can produce both standard and DR-grade pellets. The plant site has its own ship loading port located on Lake Superior.

In the second quarter of 2022, Cleveland-Cliffs temporarily idled our Northshore operations. The Northshore mine restarted production in the second quarter of 2023.
Related AssetCleveland-Cliffs 'Steelmaking segment' Operation

Owners

SourceSource
CompanyInterestOwnership
Cleveland-Cliffs Inc. 100 % Indirect
Northshore Mining Co. (operator) 100 % Direct
Northshore iron ore mining property is owned and operated by Northshore Mining Company, a direct, wholly owned subsidiary of Cliffs.

Contractors

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Deposit type

  • Banded iron formation

Summary:

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 affected the eastern Biwabik IF, resulting in a metamorphic pyroxene- and/or amphibole-dominant gangue mineralogy in place of more common silicate minerals typical of IFs. Minerals in the iron formation at Northshore include magnetite, chert, quartz, hedenbergite, cummingtonite, actinolite, hornblende, fayalite, ferrohypersthene, diopside, and andradite garnet (Gunderson and Schwartz, 1962). Contact metamorphism also resulted in a local coarsening of magnetite grain size and a decrease in the amount of quartz in the gangue mineralogy. It is believed that the silica present in primary quartz was incorporated into the iron silicate minerals found in the iron formation. Metamorphic grade is strongest to the east and decreases westward with distance from the Duluth Complex. Alteration related to metamorphism is observed to be localized along faults, on dike margins, and in fold axes. The Biwabik IF is interpreted to have experienced minor volume loss in the Eastern Mesabi Range due to loss of water and gases during thermal metamorphism (Ojakangas et al., 2009).

Contact metamorphism of the Biwabik IF at the Peter Mitchell Mine distinguishes the mineralogy from that of the rest of the Mesabi Iron Range. Emplacement of the Duluth Complex on the southeastern margin of the district resulted in re-crystallization, which increased mineral grain size and led to production of iron-rich pyroxenes, amphibole minerals, and minor olivine. Devolatilization near the contact also reduced the thickness of the proximal bedded units and altered any hydroxide minerals present.

Economic mineralization within the mine is hosted entirely within subunits of the Biwabik IF. In the mine area, bedding dips from approximately 5° southeast in the west to 35°southeast near the contact with the Duluth Complex in the east. The entire stratigraphic sequence of the Biwabik IF is present at Northshore, although only subunits of the Upper Cherty member and lesser fractions of adjacent members are mined. The Upper Cherty member averages approximately 160 ft thick, considerably thinner than equivalent stratigraphy in the western Biwabik IF.

Reserves

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Mining Methods

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Comminution

Crushers and Mills

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Processing

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Production

In the second quarter of 2022, Northshore operations were temporarily idled.
The Northshore mine restarted production in the second quarter of 2023.
CommodityUnits202320222021202020192018201720162015
Iron Ore M long tons  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe5.25.65.33.24.3
All production numbers are expressed as pellets.

Operational metrics

Metrics202320222021202020192018201720162015
Annual production capacity  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe6 M long tons of iron ore pellets6 M long tons of iron ore pellets6 M long tons of iron ore pellets6 M long tons of iron ore pellets6 M long tons of iron ore pellets
Ore tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe15,681,000 wet long tons15,385,000 wet long tons14,558,000 wet long tons9,568,000 wet long tons12,200,000 wet long tons
Waste  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe9,677,000 wet long tons8,022,000 wet long tons8,282,000 wet long tons5,049,000 wet long tons7,347,000 wet long tons
Total tonnes mined  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe
Tonnes milled  ....  Subscribe  ....  Subscribe  ....  Subscribe  ....  Subscribe15,045,388 wet long tons15,332,354 wet long tons14,503,761 wet long tons9,512,268 wet long tons12,045,587 wet long tons

Production Costs

Commodity production costs have not been reported.

Financials

Units20232022
Book Value M USD  ....  Subscribe  ....  Subscribe

Heavy Mobile Equipment

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EV - Electric

Personnel

Mine Management

Job TitleNameProfileRef. Date
....................... Subscription required ....................... Subscription required Subscription required Feb 15, 2024
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EmployeesYear
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Aerial view:

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