Mesabi Range

The Mesabi Iron Range is a mining district in northeastern Minnesota following an elongate trend containing large deposits of iron ore. It is the largest of four major iron ranges in the region collectively known as the Iron Range of Minnesota. First described in 1866, it is the chief iron ore mining district in the United States. The district is located largely in Itasca and Saint Louis counties. It has been extensively worked since 1892, and has seen a transition from high-grade direct shipping ores through gravity concentrates to the current industry exclusively producing iron ore (taconite) pellets. Production has been dominantly controlled by vertically integrated steelmakers since 1901, and therefore is dictated largely by US ironmaking capacity and demand. The Mesabi Range was known to the local Ojibwe as Misaabe-wajiw ('Giant mountain'). Throughout the Mesabi Range, Mesaba and Missabe spelling variations are found along with places containing Giant in their names. There are three iron ranges in northern Minnesota, the Cuyuna, the Vermilion, and the Mesabi. Most of the world's iron ore, including that contained in northern Minnesota, was formed during the middle Precambrian. During this period, erosion leveled mountains. This erosion released iron and silica into the waters of a new sea. Marine algae living in this new sea raised the level of atmospheric oxygen. This oxygen catastrophe caused the eroded iron to precipitate into the banded iron formations found in northern Minnesota and other members of the Animikie Group. Over billions of years, geological forces left behind ore deposits of varied quality and concentrations – differences that would determine how the ore was mined from place to place. On the Mesabi Range, stretching from Grand Rapids to Babbitt, soft ore lay close to the surface, where it could be scooped from open pit mines. The overall structure of the range is that of a monocline dipping 5 to 15 degrees to the southeast. Key faults include the Calumet, La Rue, Morton, Biwabik, and the Siphon.