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Limonite

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Formula:
FeO(OH) · nH2O
Colour:
Light brown to brown, ...
Hardness:
4 - 5½
Name:
Named in 1813 by Johann Friedrich Ludwig Hausmann from the greek λειμωυ for meadow alluding to its common occurrences in bogs.
Currently used for unidentified massive hydroxides and oxides of iron, with no visible crystals, and a yellow-brown streak. 'Limonite' is most commonly the mineral species goethite, but can also consist of varying proportions of maghemite, hematite, lepidocrocite, hisingerite, pitticite, jarosite group species, etc.

Classification of Limonite

Not Approved
Explanation of status:
It is a generic term used for undifferentiated hydrated iron oxides - often hydrated goethite.
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Occurrences of Limonite

Geological Setting:
A very common material in the oxidized zones of iron-bearing deposits, it is produced by the decomposition of many iron minerals, particularly pyrite, with water being retained in varying amounts.

Physical Properties of Limonite

Earthy
Diaphaneity (Transparency):
Opaque
Colour:
Light brown to brown, may be yellowish-brown
Streak:
Yellowish brown to red
Hardness (Mohs):
4 - 5½
Comment:
Massive may be very soft.
Density:
2.7 - 4.3 g/cm3 (Measured)    

Crystallography of Limonite

Morphology:
While "limonite" is amorphous, a number of minerals are noted for decomposing to it without losing their crystal shape - particularly pyrite crystals. Any "crystals" of "limonite" are actually pseudomorphs of other minerals which have decomposed in this fashion.

Chemical Properties of Limonite

Formula:
FeO(OH) · nH2O
Essential elements:
All elements listed in formula:
Analytical Data:
While a "generic" formula is often given as stated here, "limonite" is really quite variable in composition - both in its levels of hydration and hydroxylation and in its cationic content. There really is no formual for it...

Other Names for Limonite

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Limonite

Reference List:
Palache, Charles, Harry Berman & Clifford Frondel (1944), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Seventh edition, Volume I: 685-686.

Internet Links for Limonite

Specimens:
The following Limonite specimens are currently listed for sale on minfind.com.

Localities for Limonite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
Mineral and/or Locality  
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