What is "mountain iron"

Population (2000): 2999
Housing Units (2000): 1409
Land area (2000): 49.436691 sq. miles (128.040437 sq. km)
Water area (2000): 2.910439 sq. miles (7.538001 sq. km)
Total area (2000): 52.347130 sq. miles (135.578438 sq. km)
FIPS code: 44548
Located within: Minnesota (MN), FIPS 27
Location: 47.519227 N, 92.606463 W
ZIP Codes (1990): 55768
Note: some ZIP codes may be omitted esp. for suburbs.
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