Romanèchite
{{Short description|Baryum manganese oxide mineral}}
{{Infobox mineral
| name = Romanèchite
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| image = Romanechite.jpg
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| caption = Romanèchite, from the Marquette County, Michigan, US.
| category = Oxide minerals
| formula = {{chem2|(Ba,H2O)2(Mn(4+),Mn(3+))5O10}}
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| strunz = 4.DK.10
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| system = Monoclinic
| class = Prismatic (2/m)
(same H-M symbol)
| symmetry = C2/m
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| mohs = 6–6.5
| luster = Submetallic
| streak = Blue-black
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| references = [http://webmineral.com/data/Romanechite.shtml Romanechite], Webmineral.com[http://www.mindat.org/min-3441.html Romanechite], Mindat.org{{cite book | vauthors = Harlow G, Peters J, Prinz M | chapter = Oxides and Htdroxides. | title = Simon & Schuster's Guide to Rocks and Minerals. | location = New York | publisher = Simon & Schuster | date = 1977 }}
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File:Structure_Romanèchite.jpg
Romanèchite ({{chem2|(Ba,H2O)2(Mn(4+),Mn(3+))5O10}}) is the primary constituent of psilomelane, which is a mixture of minerals. Most psilomelane is not pure romanechite, so it is incorrect to consider them synonyms. Romanèchite is a valuable ore of manganese, which is used in steelmaking and sodium battery production.{{cite journal | vauthors = Li JY, Wu XL, Zhang XH, Lü HY, Wang G, Guo JZ, Wan F, Wang RS | display-authors = 6 | title = Romanechite-structured Na(0.31)MnO(1.9) nanofibers as high-performance cathode material for a sodium-ion battery | journal = Chemical Communications | volume = 51 | issue = 80 | pages = 14848–51 | date = October 2015 | pmid = 26344149 | doi = 10.1039/C5CC05739F | url = https://pubs.rsc.org/en/content/articlelanding/2015/cc/c5cc05739f | url-access = subscription }} It has a monoclinic crystal structure, a hardness of 6 and a specific gravity of 4.7–5. Romanèchite's structure consists of 2 × 3 tunnels formed by MnO6 octahedra.{{cite journal | vauthors = Post JE | title = Manganese oxide minerals: crystal structures and economic and environmental significance | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 7 | pages = 3447–54 | date = March 1999 | pmid = 10097056 | pmc = 34287 | doi = 10.1073/pnas.96.7.3447 | bibcode = 1999PNAS...96.3447P | doi-access = free }}
It is commonly associated with hematite, barite, pyrolusite, quartz and other manganese oxide minerals. It has been found in France, Germany, England, Brazil, Russia, India, and various parts of the United States, including Arizona, Virginia, Tennessee and Michigan, and sites throughout the Appalachian Valley and Ridge.{{Cite journal| vauthors = Carmichael SK, Doctor DH, Wilson CG, Feierstein J, McAleer RJ |date=2017-09-01|title=New insight into the origin of manganese oxide ore deposits in the Appalachian Valley and Ridge of northeastern Tennessee and northern Virginia, USA|url=https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/129/9-10/1158/207612/New-insight-into-the-origin-of-manganese-oxide-ore|journal=GSA Bulletin|language=en|volume=129|issue=9–10|pages=1158–1180|doi=10.1130/B31682.1|bibcode=2017GSAB..129.1158C |issn=0016-7606}} It occurs also in ferromanganese nodules from Lake Baikal.Manceau A, Kersten M, Marcus MA, Geoffroy N. and Granina L (2007) "Ba and Ni speciation in a nodule of binary Mn oxide phase composition from Lake Baikal". Geochimica et Cosmochimica Acta, 71: 1967–1981. {{doi|10.1016/j.gca.2007.02.007}}
File:XRF_map_Romanèchite.png|Bicolor (left) and tricolor (right) X-ray fluorescence maps of the distribution of Mn, Fe, and Ba in a ferromanganese nodule from Lake Baikal. Size = 5 mm (H) × 3 mm (V).