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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.
Sand used for mining typically had anywhere from 19% magnetite to as low as 2%. The ironsand typically had to be separated from the sand mixture. Because the magnetite is usually heavier than quartz, feldspar, or other minerals, separation was usually done by washing it in sluice boxes (a method similar to gold panning but on a larger scale).
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 ...
Placer mining is an important source of gold, ... a conspicuous shiny black mixture of iron oxides, mostly magnetite with variable amounts of ilmenite and hematite. [3]
Banded iron formation from the Barberton Greenstone Belt, South Africa. A typical banded iron formation consists of repeated, thin layers (a few millimeters to a few centimeters in thickness) of silver to black iron oxides, either magnetite (Fe 3 O 4) or hematite (Fe 2 O 3), alternating with bands of iron-poor chert, often red in color, of similar thickness.
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.
Fluidized bed magnetic roasting is the use of suspension roaster to fully mix and contact fine ore with reducing agents (such as pulverized coal, natural gas, etc.) in high temperature environment, so that the iron oxides in the ore (such as hematite, limonite, etc.) are reduced to magnetic iron minerals (mainly magnetite), thereby improving ...