Any of a group of widely occurring yellowish-brown to black iron oxide minerals, essentially FeO(OH)·nH2O, used as a minor ore of iron.
[German Limonit, from Greek leimōn, meadow.]
limonitic li'mo·nit'ic (-nĭt'ĭk) adj.
limonite
Dictionary:
li·mo·nite (lī'mə-nīt')  |
n.
Any of a group of widely occurring yellowish-brown to black iron oxide minerals, essentially FeO(OH)·nH2O, used as a minor ore of iron.
Any of a group of widely occurring yellowish-brown to black iron oxide minerals, essentially FeO(OH)·nH2O, used as a minor ore of iron.
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| Britannica Concise Encyclopedia: limonite |
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Limonite (left) from Ironwood, Mich., and (right) from Montgomery, Pa. (credit: Courtesy of the Field Museum of Natural History, Chicago; photograph, John H. Gerard/EB Inc.)
Limonite (left) from Ironwood, Mich., and (right) from Montgomery, Pa. (credit: Courtesy of the Field Museum of Natural History, Chicago; photograph, John H. Gerard/EB Inc.)
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| Sci-Tech Encyclopedia: Limonite |
A field or generic term for natural hydrous iron oxides, the most common phase being the mineral goethite, α-FeO(OH). Limonite includes the so-called bog iron ores. It is the characteristic brown stain which coats rocks containing sulfide ores, such as pyrite and pyrrhotite, in the zone of weathering of these ores referred to as a gossan. It is formed by biogenic or inorganic precipitation in bog, spring, lacustrine, or marine deposits.
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A naturally occurring mineral which is used in high-density concrete because of its high density and water content, making it effective in radiation shielding.
| Columbia Encyclopedia: limonite |
limonite (līm'ənīt) or brown hematite (hĕm'ətīt, hē'-), yellowish to dark brown mineral, a hydrated oxide of iron, FeO(OH)·nH2O, occurring commonly in deposits of secondary origin, i.e., those formed by the alteration of minerals containing iron. Both iron rust and bog iron ore are limonite. It serves as a pigment (see ocher) and as an ore of iron. It is found mainly in Austria and England.
| Rock & Mineral Guide: limonite |
FeO(OH)·nH
Amorphous
Environment
Secondary deposits resulting from weathering.
Crystal descriptionAmorphous, in botryoidal and reniform crusts, stalactites; earthy and powdery; vitreous and without discoverable internal structure. Most of the fibrous-looking material formerly called limonite is now considered goethite, even when cryptocrystalline.
Physical propertiesBrown-black to ocher-yellow. Luster glassy to dull; hardness to 5Ɖ; specific gravity 2.7-4.3; streak brown to yellow; fracture conchoidal to earthy; cleavage none. Crumbly to brittle.
CompositionAn omnibus name for an assemblage of hydrous ferric oxides; of indefinite composition.
TestsSame as for goethite (preceding).
Distinguishing characteristicsEssentially the same as goethite, but it does not show any sort of fibrous or silky appearance on a fresh break. Distinguished from its manganese counterpart (wad) by the streak, and the magnetism after heating.
OccurrenceLimonite is the coloring matter of soils, forming from iron minerals at surface temperatures as the rocks weather. It stains weathered rock, forms dendrites on rock seams, and colors agate and jasper. Soluble in several acids; oxalic acid is one of the best for cleaning limonite-stained crystals (unlike hydrochloric acid, it leaves no subsequent rusting residue). Alters to hematite quite easily through a loss of water. Soils with slightly higher ambient temperatures are red, not brown (as in U.S. south of Virginia).
Limonite is a usefully ambiguous term, best retained for use when we are speaking of undistinguished hydrous iron oxides or mixtures of several.
| Wikipedia: Limonite |
Limonite is an ore consisting in a mixture of hydrated iron(III) oxide-hydroxide of varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide.
Together with hematite, it has been mined as ore for the production of iron. Limonite is heavy and yellowish-brown. It is a very common amorphous substance though can be tricky to find when mined with hematite and bog ore.
It is not a true mineral and it is composed by a mixture of similar hydrated iron oxide minerals, mostly goethite with lepidocrocite, jarosite, and others. Limonite forms mostly in or near oxidized iron and other metal ore deposits and as sedimentary beds. Limonite may occur as the cementing material in iron rich sandstones. Also known as the Lemon Rock.
It is never crystallized into macroscopic crystals, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms or in compact and earthy masses; sometimes mammillary, botryoidal, reniform or stalactitic. The colour presents various shades of brown and yellow, and the streak is always brownish, a character which distinguishes it from hematite with a red, or from magnetite with a black streak. It is sometimes called brown hematite or brown iron ore.
Limonite has been known to form pseudomorphs after other minerals such as pyrite, meaning that the chemical weathering transforms the crystal of pyrite into limonite but keeps the external shape of the pyrite crystal. It has also been formed from other iron oxides, hematite and magnetite; the carbonate siderite and iron rich silicates like some garnets.
It is named from the Greek word for meadow (λειμών), in allusion to its occurrence as "bog-ore" in meadows and marshes.
The hardness is variable, but generally in the 4 - 5.5 range. The specific gravity varies from 2.9 to 4.3.
Uses of limonite
In the past bog ore or brown iron ore were mined as a source of iron. Iron caps or gossans of siliceous iron oxide typically forms as the result of intensive oxidation of sulfide ore deposits. These gossans were used by prospectors as guides to buried ore. In addition the oxidation of sulfide deposits which contained gold mineralization often resulted in the concentration of gold in the iron oxide and quartz of the gossans.
Gold bearing limonite gossans were productively mined in the Shasta County, California mining district. Similar deposits were mined near Rio Tinto in Spain and Mount Morgan in Australia. In the Dahlonega gold belt in Lumpkin County, Georgia gold was mined from limonite rich lateritic or saprolite soil. The gold of the primary veins was concentrated into the limonites of the deeply weathered rocks. In another example the deeply weathered iron formations of Brazil served to concentrate gold with the limonite of the resulting soils.
Limonite from occurrences with consistent color is used as the yellow-brown natural earth pigment ochre.
See also
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 | bean ore (geology) |
| yellow ocher, yellow ochre |
| relief limonite (mineralogy) |
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved. Read more |
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| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved. Read more |
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| Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/. Read more |
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| Rock & Mineral Guide. Peterson Field Guide to Rocks and Minerals, by Frederick H. Pough. Copyright © 1998 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Limonite". Read more |
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Mentioned in
- bean ore (geology)
- yellow ocher, yellow ochre
- relief limonite (mineralogy)
- brown clay ironstone (geology)
- indigenous limonite (mineralogy)
- mountain brown ore (geology)
- heavyweight aggregate
- lepidocrocite (mineralogy)
- pea ore (mineralogy)
- residual ochre (geology)
- boxwork (geology)
- clay ironstone (petrology)
- goethite (mineralogy)
- allomorph
