Hematite

Source: Wikipedia, the free encyclopedia.
This article is about the mineral. For other uses, see Hematite (disambiguation).
Hematite
Specific gravity
5.26
Density5.3
Optical propertiesUniaxial (−)
Refractive indexnω = 3.150–3.220, nε = 2.870–2.940
Birefringenceδ = 0.280
PleochroismO: brownish red; E: yellowish red
References[3][4][5]

Hematite (/ˈhiːməˌtaɪt, ˈhɛmə-/), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils.[6] Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of Fe
2O
3. It has the same crystal structure as corundum (Al
2O
3) and ilmenite (FeTiO
3). With this it forms a complete solid solution at temperatures above 950 °C (1,740 °F).

Hematite naturally occurs in black to steel or silver-gray, brown to reddish-brown, or red colors. It is

spinel structure
like magnetite.

Large deposits of hematite are found in banded iron formations. Gray hematite is typically found in places that have still, standing water or mineral hot springs, such as those in Yellowstone National Park in North America. The mineral can precipitate in the water and collect in layers at the bottom of the lake, spring, or other standing water. Hematite can also occur in the absence of water, usually as the result of volcanic activity.

tropical
, ancient, or otherwise highly weathered soils.

Etymology and history

Main article: Ochre

The name hematite is derived from the Greek word for blood αἷμα (haima), due to the red coloration found in some varieties of hematite.[6] The color of hematite is often used as a pigment. The English name of the stone is derived from Middle French hématite pierre, which was taken from Latin lapis haematites c. the 15th century, which originated from Ancient Greek αἱματίτης λίθος (haimatitēs lithos, "blood-red stone").

Ochre is a clay that is colored by varying amounts of hematite, varying between 20% and 70%.[8] Red ochre contains unhydrated hematite, whereas yellow ochre contains hydrated hematite (Fe2O3 · H2O). The principal use of ochre is for tinting with a permanent color.[8]

The

Pinnacle-Point man, possibly for social purposes.[9] Hematite residues are also found in graves from 80,000 years ago. Near Rydno in Poland and Lovas in Hungary red chalk mines have been found that are from 5000 BC, belonging to the Linear Pottery culture at the Upper Rhine.[10]

Rich deposits of hematite have been found on the island of

Etruscans.[11]

Underground hematite mining is classified as carcinogenic hazard to humans. [12]

Magnetism

Hematite shows only a very feeble response to a

paramagnetic
.

The magnetic structure of α-hematite was the subject of considerable discussion and debate during the 1950s, as it appeared to be ferromagnetic with a Curie temperature of approximately 1,000 K (730 °C), but with an extremely small

nanoparticles and is attributed to the presence of impurities, water molecules and defects in the crystals lattice. Hematite is part of a complex solid solution oxyhydroxide system having various contents of H2O (water), hydroxyl groups and vacancy substitutions that affect the mineral's magnetic and crystal chemical properties.[15]
Two other end-members are referred to as protohematite and hydrohematite.

Enhanced

magnetic coercivities for hematite have been achieved by dry-heating a two-line ferrihydrite precursor prepared from solution. Hematite exhibited temperature-dependent magnetic coercivity values ranging from 289 to 5,027 oersteds (23–400 kA/m). The origin of these high coercivity values has been interpreted as a consequence of the subparticle structure induced by the different particle and crystallite size growth rates at increasing annealing temperature. These differences in the growth rates are translated into a progressive development of a subparticle structure at the nanoscale (super small). At lower temperatures (350–600 °C), single particles crystallize. However, at higher temperatures (600–1000 °C), the growth of crystalline aggregates, and a subparticle structure is favored.[16]

  • A microscopic picture of hematite
    A microscopic picture of hematite
  • Crystal structure of hematite
    Crystal structure of hematite

Mine tailings

Hematite is present in the waste

iron mines. A recently developed process, magnetation, uses magnets to glean waste hematite from old mine tailings in Minnesota's vast Mesabi Range iron district.[17] Falu red is a pigment used in traditional Swedish house paints. Originally, it was made from tailings of the Falu mine.[18]

Mars

Image mosaic from the Mars Exploration Rover Microscopic Imager shows Hematite spherules partly embedded in rock at the Opportunity landing site. Image is around 5 cm (2 in) across.

The spectral signature of hematite was seen on the planet

spherules are apparently concretions
formed from a water solution. "Knowing just how the hematite on Mars was formed will help us characterize the past environment and determine whether that environment was favorable for life".[24]

Jewelry

Hematite is often shaped into beads, tumbling stones, and other jewellery components.

intaglio engraved gems. Hematine is a synthetic material sold as magnetic hematite.[27]

Pigment

Hematite has been sourced to make pigments since earlier origins of human pictorial depictions, such as on cave linings and other surfaces, and has been continually employed in artwork through the eras. It forms the basis for red, purple and brown iron-oxide pigments, as well as being an important component of ochre, sienna and umber pigments.[28]

Industrial purposes

As mentioned earlier, hematite is an important mineral for iron ore. The physical properties of hematite are also employed in the areas of medical equipment, shipping industries and coal production. Having high density and capable as an effective barrier for X-ray passage, it is often incorporated into radiation shielding. As with other iron ores, it is often a component of ship ballasts for its density and economy. In the coal industry, it can be formed into a high specific density solution, to help separate coal powder from impurities.[29]

Gallery

  • A rare pseudo-scalenohedral crystal habit
    A rare pseudo-scalenohedral crystal habit
  • Three gemmy quartz crystals containing bright rust-red inclusions of hematite, on a field of sparkly black specular hematite
    Three gemmy quartz crystals containing bright rust-red inclusions of hematite, on a field of sparkly black specular hematite
  • Golden acicular crystals of rutile radiating from a center of platy hematite
    Golden acicular crystals of rutile radiating from a center of platy hematite
  • Cypro-Minoan cylinder seal (left) made from hematite with corresponding impression (right), approximately 14th century BC
    Cypro-Minoan cylinder seal (left) made from hematite with corresponding impression (right), approximately 14th century BC
  • A cluster of parallel-growth, mirror-bright, metallic-gray hematite blades from Brazil
    A cluster of parallel-growth, mirror-bright, metallic-gray hematite blades from Brazil
  • Hematite carving, 5 cm (2 in) long
    Hematite carving, 5 cm (2 in) long
  • Hematite, variant specularite (specular hematite), with fine grain shown
    Hematite, variant specularite (specular hematite), with fine grain shown
  • Red hematite from banded iron formation in Wyoming
    Red hematite from banded iron formation in Wyoming
  • Hematite on Mars as found in form of "blueberries" (named by NASA)
    Hematite on Mars as found in form of "blueberries" (named by NASA)
  • Streak plate, showing that Hematite consistently leaves a rust-red streak.
    Streak plate, showing that Hematite consistently leaves a rust-red streak.
  • Hematite in Scanning Electron Microscope, magnification 100x.
    Hematite in Scanning Electron Microscope, magnification 100x.
  • Micaceous hematite taken with permission from Kelly's Mine, Lustleigh, Devon UK
    Micaceous hematite taken with permission from Kelly's Mine, Lustleigh, Devon UK

See also

References

  1. ISBN 9780521000987
    .
  2. S2CID 235729616
    .
  3. ISBN 978-0962209727
    . Retrieved December 22, 2018.
  4. ^ "Hematite Mineral Data". WebMineral.com. Retrieved December 22, 2018.
  5. ^ "Hematite". Mindat.org. Retrieved December 22, 2018.
  6. ^
    LCCN 96031931
    . Retrieved December 22, 2018.
  7. ^ a b Morgenthau, Mengo L. (1923). Minerals and Cut Stones: Reference Book Containing Condensed and Simplified Descriptions from Standard Works on Mineralogy. p. 23.
  8. ^ a b "Ochre". Industrial Minerals. Minerals Zone. Archived from the original on November 15, 2016. Retrieved December 22, 2018.
  9. ^ "Researchers find earliest evidence for modern human behavior in South Africa" (Press release). AAAS. ASU News. October 17, 2007. Retrieved December 22, 2018.
  10. ^ Levato, Chiara (2016). "Iron Oxides Prehistoric Mines: A European Overview" (PDF). Anthropologica et Præhistorica. 126: 9–23. Retrieved December 22, 2018.
  11. doi:10.1111/j.1475-4754.2012.00692.x
    .
  12. ^ https://monographs.iarc.who.int/list-of-classifications
  13. doi:10.1016/0022-3697(58)90076-3
    .
  14. doi:10.1103/PhysRev.120.91
    .
  15. S2CID 94031594
    .
  16. S2CID 137598876
    .
  17. ^ Redman, Chris (May 20, 2009). "The next iron rush". Money.cnn.com. Retrieved December 22, 2018.
  18. ^ "Sveriges mest beprövade husfärg" [Sweden's most proven house color] (in Swedish). Retrieved December 22, 2018.
  19. ^ "Mars Global Surveyor TES Instrument Identification of Hematite on Mars" (Press release). NASA. May 27, 1998. Archived from the original on May 13, 2007. Retrieved December 22, 2018.
  20. doi:10.1029/2003JE002233
    .
  21. doi:10.1029/2001JE001510
    .
  22. S2CID 53489327
    .
  23. Bibcode:2005LPI....36.2159G
    .
  24. ^ "Hematite". NASA. Retrieved December 22, 2018.
  25. ^ "Hematite: A primary ore of iron and a pigment mineral". geology.com. Retrieved 2023-09-07.
  26. ISBN 978-1-55297-814-6
    .
  27. ^ "Magnetic Hematite". Mindat.org. Retrieved December 22, 2018.
  28. ^ "Colors from the Earth: Violet Hematite". www.naturalpigments.com. Retrieved 2023-09-07.
  29. ^ "Hematite: A primary ore of iron and a pigment mineral". geology.com. Retrieved 2023-09-07.

External links

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