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As of 2019, magnetite iron ore is mined in Minnesota and Michigan in the United States, eastern Canada, and northern Sweden. [8] Magnetite-bearing banded iron formation is mined extensively in Brazil as of 2019, which exports significant quantities to Asia, and there is a nascent and large magnetite iron ore industry in Australia.
Horizons containing magnetite as the dominant mineral have been extensively mined since 1955 to produce iron ore pellets; the term 'taconite' has consequently been colloquially adapted to describe the magnetite iron-formation ores (taconite iron ore), the mining, milling, magnetic separation, and agglomerating process (taconite process), and ...
This is a magnetite or hematite chert. Natural ore deposits are located in synclines and up against mafic dikes. Beneficiation commenced in 1954 [2] and this concentration of iron into pellets accounted for 73 percent of production by 1965. Early mining used open-pit mining methods, but was replaced with underground mining by 1880. [3]
Iron ore was the third-highest-value metal mined in the United States, after gold and copper. [2] Iron ore was mined from nine active mines and three reclamation operations in Michigan, Minnesota, and Utah. Most of the iron ore was mined in northern Minnesota's Mesabi Range. Net exports (exports minus imports) were 3.9 million tons.
Magnetite has been important in understanding the conditions under which rocks form. Magnetite reacts with oxygen to produce hematite, and the mineral pair forms a buffer that can control how oxidizing its environment is (the oxygen fugacity). This buffer is known as the hematite-magnetite or HM buffer.
The ore body at Benson Mine is composed of magnetite and non-magnetite ore. The average percentage of iron in both magnetite and non-magnetite ore was about 23%, less than the 40% at Chateauguay. Iron-ore deposits that contained 50% or more iron were depleted in the United States by the mid-1940s.
But on the Mesabi and Cuyuna Ranges, iron mining operations evolved into enormous open pit mines, where steamshovels and other industrial machines could remove massive amounts of ore. "Large-scale commercial production of magnetite taconite ore on the Mesabi Range started in 1956 at the Peter Mitchell Mine near Babbitt, Minnesota." [2]
But there was limited use of native (unsmelted) iron ore, from magnetite, iron pyrite and ilmenite (iron–titanium), especially in the Andes (Chavin and Moche cultures) and Mesoamerica, after 900 BC and until c. 500 CE. Various forms of iron ore were mined, [30] drilled and highly polished.