Editing Limonite (section)

==Characteristics==
Limonite is relatively [[density|dense]] with a [[specific gravity]] varying from 2.7 to 4.3.<ref name="Northrop">Northrop, Stuart A. (1959) "Limonite" ''Minerals of New Mexico'' (revised edition) University of New Mexico Press, Albuquerque, New Mexico, pp. 329&ndash;333, {{OCLC|2753195}}</ref> It is usually medium to dark yellowish brown in color. The [[Streak (mineralogy)|streak]] of limonite on an unglazed porcelain plate is always yellowish brown, a character which distinguishes it from hematite with a red streak, or from magnetite with a black streak. The [[Mohs scale of mineral hardness|hardness]] is quite variable, ranging from 1 to 5. In thin section it appears as red, yellow, or brown and has a high index of refraction, 2.0–2.4. Limonite minerals are strongly birefringent, but grain sizes are usually too small for this to be detectable.<ref name=Nesse2000>{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916 |pages=371–372}}</ref>

Although originally defined as a single mineral, limonite is now recognized as a [[Field work|field]] term for a mixture of related [[hydrate]]d [[iron oxide]] minerals,<ref>{{cite book |last1=Klein |first1=Cornelis |last2=Hurlbut |first2=Cornelius S. Jr. |title=Manual of mineralogy : (after James D. Dana) |date=1993 |publisher=Wiley |location=New York |isbn=047157452X |edition=21st}}</ref> among them [[goethite]], [[lepidocrocite]],<ref name=Nesse2000/> [[akaganeite]],<ref>{{cite journal |last1=Mackay |first1=A. L. |title=β-Ferric oxyhydroxide—akaganéite |journal=Mineralogical Magazine and Journal of the Mineralogical Society |date=December 1962 |volume=33 |issue=259 |pages=270–280 |doi=10.1180/minmag.1962.033.259.02|bibcode=1962MinM...33..270M }}</ref> and [[jarosite]].<ref>{{cite journal |last1=Zuo |first1=Pengfei |last2=Sun |first2=Jiangtao |last3=Liu |first3=Xuefei |last4=Hao |first4=Jinhua |last5=Zheng |first5=Deshun |last6=Li |first6=Yu |title=Two types of jarosite in the early Cambrian sedimentary rocks: Insights for genesis and transformation of jarosite on Mars |journal=Icarus |date=November 2021 |volume=369 |pages=114651 |doi=10.1016/j.icarus.2021.114651|bibcode=2021Icar..36914651Z }}</ref> Determination of the precise mineral composition is practical only with [[X-ray diffraction]] techniques.<ref name=Nesse2000/> Individual minerals in limonite may form [[crystal]]s, but limonite does not, although specimens may show a fibrous or [[microcrystalline]] structure,<ref>Boswell, P. F. and Blanchard, Roland (1929) "Cellular structure in limonite" ''Economic Geology'' 24(8):&nbsp;pp.&nbsp;791&ndash;796</ref> and limonite often occurs in concretionary forms or in compact and earthy masses; sometimes mammillary, [[botryoidal]], reniform or stalactitic.  Because of its amorphous nature, and occurrence in hydrated areas limonite often presents as a clay or mudstone. However, there are limonite [[pseudomorph]]s after other minerals such as [[pyrite]].<ref name="Northrop" /> This means that chemical weathering transforms the crystals of pyrite into limonite by hydrating the molecules, but the external shape of the pyrite crystal remains. Limonite pseudomorphs have also been formed from other iron oxides, hematite and magnetite; from the carbonate [[siderite]] and from iron rich silicates such as [[Almandine|almandine garnets]].

<gallery widths="200px" heights="170px">
File:La Palma Limonit.jpg|Limonite deposited from mine runoff
File:Galena Limonite.jpg|[[Galena]] and limonite
File:GranadaEZ.jpg|Limonite pseudomorphs after garnet
</gallery>