Banded Iron Formation (Magnetite and Hematite) ID'd
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This video features the rock
This video features the rock called Banded Iron Formation (sometimes called "BIF")--which contains magnetite and hematite. This video uses 360 degree photography. Banded iron formation is an ancient sedimentary rock. It tends to form a layered rock with both black and rusty-red layers (although the entire rock may be weathered into rusty red in colors). The layers may also contain some chert.
These rocks are ancient marine rocks that are roughly two billion years old or older (although local deposits can be much older or younger than this). These formed during the transitional time when Earth's early atmosphere was changing from anoxic- to- more oxygen rich. The limited oxygen in Earth's early atmosphere, progressively entered into marine water in oceans, as dissolved oxygen. This caused iron dissolved within the water to precipitate--into the layered sedimentary structures. Some banded iron formation deposits are more granular than microscopic in sedimentary structure. However, other types of sediments are mixed into the layers of the banded iron formation too.
Banded iron formation is a layered mix of magnetite, hematite, and other sediments. Therefore, it is slightly magnetic (compared to pure magnetite minerals). The amount of magnetism can be stronger or weaker--from layer to layer within the rock (because non-iron sediment is also mixed into this rock type). Banded iron formation often forms large iron deposits. If enough magnetite is located near to the Earth's surface, it may locally surmount Earth's general magnetism. There are stories of early explorers in northern Minnesota becoming confused, disoriented, and lost, because the local magnetism (from near-surface banded iron formation rocks) affected their compasses. The local magnetism in the rocks, caused the direction that their compass needles pointed--which would vary from the general north-south oriented magnetism on Earth (although this story is often exaggerated).
Banded iron formation rocks are not pure iron, but often form large deposits of iron ore. Therefore, iron mines typically locate in banded iron formation rock deposits. These rocks form the most common iron deposit for iron mines on Earth. Because these rocks can vary in the relative abundance of either magnetite or hematite, most mines prefer deposits containing more magnetite than hematite. This is because the separation of iron from the iron ore is much more efficient and cheap--by simply using magnets. Although hematite contains about the same amount of iron as magnetite, magnetic separation does not work (hematite is non-magnetic). With hematite, the less efficient and more expensive method of separating iron from the ore, uses density separation methods.
Hello Rock People! This is Dave the Geology Dude. Identification notes are below in this text. Note that I have other videos that provide more rock identification information on my YouTube channel. Don't forget that: Geology isn't Rocket Science--it's Rock Science! Please "like" and subscribe to this YouTube channel!
Identification information for this rock:
1) environment: magnetite is most commonly found in ancient "banded iron formation" rocks, such as in northern Minnesota and northern Michigan, Australia, and other countries.
2) Shape/cleavages: The iron in Banded Iron Formation typically is microscopic to granular. Therefore it will appear to have no cleavages--it fractures and usually is not found in crystal form. Note that some Banded Iron Formation may have some very small crystals in certain places, but generally the crystals do not exist.
3) Color/luster--typically has a layered metallic black, metallic grayish-sliver, and dark rusty red colors. It can rust into various rusty reddish brown colors, and the rusty colors often run downward to discolor other nearby rocks
4) density--it is up to five times more heavy than water, which is about twice the weight or density than most common rocks.
5) hardness--magnetite and hematite has about the same hardness as glass. It can cut glass slightly, or intermittently
6) acid reactivity: will not react to acid contact
7) It is often confused as only magnetite or only hematite. Banded Iron Formation often is a mixture of both magnetite and hematite, although one of these minerals may be more dominant in areas, than the other mineral
8) Summary: if a dark or rusty rock appears to 1) look like iron, 2) it is more dense than most rocks, 3) a magnet will "stick" to the surface of the rock (although perhaps more weakly than pure magnetite), and it appears like layers of black, gray, and rusty red colors--it is probably banded iron formation.
Music (Youtube Audio Library): Stars Align (by The 126ers)
Copyright by David Knoblach, 2022. All rights reserved
These rocks are ancient marine rocks that are roughly two billion years old or older (although local deposits can be much older or younger than this). These formed during the transitional time when Earth's early atmosphere was changing from anoxic- to- more oxygen rich. The limited oxygen in Earth's early atmosphere, progressively entered into marine water in oceans, as dissolved oxygen. This caused iron dissolved within the water to precipitate--into the layered sedimentary structures. Some banded iron formation deposits are more granular than microscopic in sedimentary structure. However, other types of sediments are mixed into the layers of the banded iron formation too.
Banded iron formation is a layered mix of magnetite, hematite, and other sediments. Therefore, it is slightly magnetic (compared to pure magnetite minerals). The amount of magnetism can be stronger or weaker--from layer to layer within the rock (because non-iron sediment is also mixed into this rock type). Banded iron formation often forms large iron deposits. If enough magnetite is located near to the Earth's surface, it may locally surmount Earth's general magnetism. There are stories of early explorers in northern Minnesota becoming confused, disoriented, and lost, because the local magnetism (from near-surface banded iron formation rocks) affected their compasses. The local magnetism in the rocks, caused the direction that their compass needles pointed--which would vary from the general north-south oriented magnetism on Earth (although this story is often exaggerated).
Banded iron formation rocks are not pure iron, but often form large deposits of iron ore. Therefore, iron mines typically locate in banded iron formation rock deposits. These rocks form the most common iron deposit for iron mines on Earth. Because these rocks can vary in the relative abundance of either magnetite or hematite, most mines prefer deposits containing more magnetite than hematite. This is because the separation of iron from the iron ore is much more efficient and cheap--by simply using magnets. Although hematite contains about the same amount of iron as magnetite, magnetic separation does not work (hematite is non-magnetic). With hematite, the less efficient and more expensive method of separating iron from the ore, uses density separation methods.
Hello Rock People! This is Dave the Geology Dude. Identification notes are below in this text. Note that I have other videos that provide more rock identification information on my YouTube channel. Don't forget that: Geology isn't Rocket Science--it's Rock Science! Please "like" and subscribe to this YouTube channel!
Identification information for this rock:
1) environment: magnetite is most commonly found in ancient "banded iron formation" rocks, such as in northern Minnesota and northern Michigan, Australia, and other countries.
2) Shape/cleavages: The iron in Banded Iron Formation typically is microscopic to granular. Therefore it will appear to have no cleavages--it fractures and usually is not found in crystal form. Note that some Banded Iron Formation may have some very small crystals in certain places, but generally the crystals do not exist.
3) Color/luster--typically has a layered metallic black, metallic grayish-sliver, and dark rusty red colors. It can rust into various rusty reddish brown colors, and the rusty colors often run downward to discolor other nearby rocks
4) density--it is up to five times more heavy than water, which is about twice the weight or density than most common rocks.
5) hardness--magnetite and hematite has about the same hardness as glass. It can cut glass slightly, or intermittently
6) acid reactivity: will not react to acid contact
7) It is often confused as only magnetite or only hematite. Banded Iron Formation often is a mixture of both magnetite and hematite, although one of these minerals may be more dominant in areas, than the other mineral
8) Summary: if a dark or rusty rock appears to 1) look like iron, 2) it is more dense than most rocks, 3) a magnet will "stick" to the surface of the rock (although perhaps more weakly than pure magnetite), and it appears like layers of black, gray, and rusty red colors--it is probably banded iron formation.
Music (Youtube Audio Library): Stars Align (by The 126ers)
Copyright by David Knoblach, 2022. All rights reserved
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