Where is Magnetite-bearing rock found?
Magnetite (Fe3O4) in a sedimentary or metamorphic rock matrix
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Open the appMagnetite-bearing rock occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Magnetite-bearing rock
Lake Superior Region, USA and Canada
World-class deposits of Banded Iron Formations (BIFs), particularly the Mesabi Range in Minnesota, USA, and the Labrador Trough in Canada, are major sources of magnetite-bearing taconite.
Hamersley Basin, Western Australia
Contains vast deposits of Archean and Proterozoic BIFs, forming some of the largest iron ore reserves globally.
Kiruna, Sweden
Known for its large, high-grade magnetite-apatite iron ore deposits, formed through magmatic or hydrothermal processes.
Brazil (Minas Gerais)
Significant deposits of high-grade iron ore, including magnetite-rich varieties, are found in the 'Iron Quadrangle'.
China (Anshan, Bayan Obo)
Numerous iron ore deposits, including magnetite-rich BIFs and other types, are found across China.
Collecting tips
- Magnetic Test. The most definitive field test is to use a strong magnet. Magnetite is strongly ferromagnetic and will attract a magnet. This distinguishes it from hematite, which is only weakly magnetic or non-magnetic.
- Color and Streak. Look for dark gray to black rocks. The streak of magnetite is black, which can help differentiate it from hematite (reddish-brown streak).
- Geological Context. Search in areas known for ancient sedimentary basins (for BIFs) or metamorphic terrains. Look for layered or banded structures in sedimentary rocks, or dark, dense, and magnetic rocks in metamorphic settings.
- Density. Magnetite-bearing rocks are typically denser than average rocks due to the high specific gravity of magnetite. This can be noticeable when handling samples.
Quick Check
- Color:
- Dark gray to black
- Luster:
- Dull to submetallic (rock), metallic to submetallic (magnetite grains)
- Streak:
- Black
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