Goethite

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Goethite
Specific gravity
3.3–4.3
Refractive indexOpaque to sub-translucent
FusibilityFusible at 5–5.5
SolubilityHCl soluble
Other characteristicsweakly magnetic
References[2][3][4][5]
Unusual specimen of goethite replacing a gypsum stalactite; the center is hollow. From Santa Eulalia, Chihuahua, Mexico.

Goethite (

polymorph. It is found in soil and other low-temperature environments such as sediment. Goethite has been well known since ancient times for its use as a pigment (brown ochre). Evidence has been found of its use in paint pigment samples taken from the caves of Lascaux in France. It was first described in 1806 based on samples found in the Hollertszug Mine in Herdorf, Germany.[4] The mineral was named after the German polymath and poet Johann Wolfgang von Goethe
(1749–1832).

Composition

Goethite is an

specific gravity varies from 3.3 to 4.3. The mineral forms prismatic needle-like crystals ("needle ironstone"[3]) but is more typically massive.[2]

polymorphs of the iron oxyhydroxide FeO(OH) which are stable at the pressure and temperature conditions of the Earth's surface. Although they have the same chemical formula as goethite, their different crystalline structures make them distinct minerals.[5]

Additionally, goethite has several high-pressure and high-temperature

polymorphs, which may be relevant to the conditions of the Earth's interior. These include ε-FeOOH, which has an orthorhombic crystal structure,[10] a cubic pyrite-type polymorph with[11] or without losing hydrogen[12] and an ultradense hexagonal structure.[13]

Goethite has the same crystal structure as diaspore, the analogous aluminium oxide-hydroxide mineral. Oxygen and hydroxide ions form a hexagonal close-packed structure, with iron ions filling octahedral sites between the anions. The sites filled by iron ions form paired chains running the length of the crystal, with the two chains in each pair joined by hydroxide ions.[14]

  • The goethite crystal structure viewed along [001]. Red ions are iron, white are oxygen, and yellow are hydroxide.
    The goethite crystal structure viewed along [001]. Red ions are iron, white are oxygen, and yellow are hydroxide.
  • The goethite crystal structure viewed along [010]
    The goethite crystal structure viewed along [010]

Formation

A microscopic picture of Goethite (name misspelled on picture)

Goethite often forms through the

hydrothermal deposits. Goethite has also been found to be produced by the excretion processes of certain bacteria types.[16]

Distribution

Goethite is found all over the planet, usually in the form of

oxidation of sulfide ore deposits is formed of goethite along with other iron oxides and quartz.[17][2]

Significant deposits of goethite are found in England; Cuba; and Minnesota, Missouri, Colorado, Alabama, Georgia, Virginia, and Tennessee, in the United States.[17][2]

Deposits significant in location, if not in abundance, have been found in the

Spirit rover, providing strong evidence for the presence of liquid water on the planet in an earlier stage of its evolution.[18]

tensile strength of 3.5–6.0 GPa and elastic modulus of 120±30 GPa.[19] [20]

Usage

Its main modern use is as an iron ore, being referred to as brown iron ore.[4] Goethite is an important component of ochre pigments,[21] and has been heat-treated for use as a red pigment since Paleolithic times.[22] Iron-rich lateritic soils that have developed over serpentinite rocks in tropical climates are mined for their iron content, as well as other metals.[23]

Fine goethite specimens are rare and therefore are valued collectibles.

cabochons for jewelry making.[24]

In a royal tomb of the ancient kingdom of Phrygia, a body was found believed to be King Gordias, father of the legendary King Midas. The burial shroud had been colored with a dye containing goethite, which in its original unfaded state would have made the shroud look like it was woven from gold. Historians speculate that the legend of King Midas' golden touch might have originated from Phrygian royalty wearing clothes made from such golden-colored textiles.[25][26]

Gallery

  • Iridescent goethite, Filón Sur Mine, Tharsis, Huelva, Spain
    Iridescent goethite, Filón Sur Mine, Tharsis, Huelva
    , Spain
  • Goethite from Minas Gerais, Brazil
    Goethite from Minas Gerais, Brazil
  • A sharp, disc-shaped calcite has here been completely replaced by goethite, which preserved the original form perfectly
    A sharp, disc-shaped calcite has here been completely replaced by goethite, which preserved the original form perfectly
  • Goethite coating/replacing rusted pyrite cubes
    Goethite coating/replacing rusted pyrite cubes
  • Finely crystallized specimen of goethite from Lake George, Park County, Colorado, US
    Finely crystallized specimen of goethite from Lake George, Park County, Colorado, US
  • Goethite from Negaunee, Marquette County, Michigan
    Goethite from Negaunee, Marquette County, Michigan

See also

References

  1. S2CID 235729616
    .
  2. ^
    ISBN 0-471-80580-7
    .
  3. ^ a b Barthelmy, David (2012). "Goethite Mineral Data". Mineralogy Database. Retrieved 8 April 2022.
  4. ^ a b c d Goethite, Mindat.org
  5. ^ a b Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Goethite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Archived (PDF) from the original on 2022-10-09. Retrieved 14 March 2022.
  6. ^ "goethite". Lexico UK English Dictionary. Oxford University Press. Archived from the original on August 5, 2021.
  7. ^ "goethite". Merriam-Webster.com Dictionary.
  8. ^ "goethite". Dictionary.com Unabridged (Online). n.d.
  9. ^ "goethite". The American Heritage Dictionary of the English Language (5th ed.). HarperCollins.
  10. S2CID 92941002
    .
  11. S2CID 10702618
    .
  12. S2CID 205257075
    .
  13. PMID 29507221
    .
  14. ^ Hurlbut & Klein 1985, p. 392.
  15. S2CID 130357956
    .
  16. doi:10.1016/j.gca.2010.03.037
    .
  17. ^
    ISBN 0442276249
    .
  18. S2CID 95186141
    .
  19. ^ Webb, Jonathan (18 February 2015). "Limpet teeth set new strength record". BBC News: Science and Environment. BBC News. Retrieved 23 December 2016.
  20. PMID 25694539
    .
  21. doi:10.1016/S0169-1317(03)00076-0
    .
  22. doi:10.1111/arcm.12360
    .
  23. doi:10.2113/gsecongeo.36.3.280
    .
  24. doi:10.1080/00357529.1968.11765131
    .
  25. ISBN 9781934536483
    . Retrieved 8 April 2022.
  26. ^ Archived at Ghostarchive and the Wayback Machine: Rose, Brian. "Great Myths and Legends: The Golden Age of King Midas". Penn Museum. Retrieved 27 August 2016.

External links

Wikimedia Commons has media related to Goethite.
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