{{Infobox mineral | name = Ericssonite | image = | category = Sorosilicates | formula = BaMn<sub>2</sub>FeO[Si<sub>2</sub>O<sub>7</sub>](OH) | IMAsymbol = Ers<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | system = Monoclinic | class = Prismatic (2/m) <br/><small>(same H-M symbol)</small> | symmetry = ''C2/m'' | unit cell = a= 20.42, b= 7.03 <br/>c= 5.34 [Å], β= 95.5°; Z = 4 | color = deep reddish black | habit = Massive - uniformly indistinguishable crystals forming large masses | cleavage = perfect, perfect on (100) fair on (011) | tenacity = very brittle | mohs = 4.5 | luster = sub metallic | streak = brown | density = 4.21 | diaphaneity = Translucent to opaque | other = weakly magnetic | refractive = 1.802-1.891 | pleochroism = x= pale greenish tan, y= red-brown, z= deep brown }} thumb '''Ericssonite''' has a general formula of BaMn<sub>2</sub>FeO[Si<sub>2</sub>O<sub>7</sub>](OH).<ref>{{Cite web|url=http://www.mindat.org/min-1397.html|title = Ericssonite}}</ref> It was discovered in 1967 and named after John Ericsson (July 31, 1803 – March 8, 1889), a well known Swedish American inventor, engineer and designer of the iron-clad ship USS ''Monitor''.<ref>{{Cite web|url=http://webmineral.com/data/Ericssonite.shtml|title=Ericssonite Mineral Data}}</ref> Ericssonite was discovered in the Jakobsberg Mine in Värmland, Sweden.<ref>{{Cite web|url=http://www.mindat.org/loc-3197.html|title=Jakobsberg Mine, Nordmark, Filipstad, Värmland, Sweden|work=Mindat}}</ref>
Ericcsonite is monoclinic; this means it contains three unequal vectors, two of these vector angles are perpendicular while the other is at an angle greater than 90°.<ref>Roberts, W.L., Campbell, T.J., and Rapp Jr, G.R. (1990) Encyclopedia of Minerals (2nd Edition). 294 p. Library of Congress Cataloging, Washington, D.C.</ref> Optically ericssonite is anisotropic which means that the mineral has more than one index of refraction, causing light to vary in speed depending on which axis it is traveling through. Since ericssonite is monoclinic, containing three unequal vectors, it has three indices of refraction. Ericssonite is usually a deep reddish-black in color. <ref>{{Cite web|url=https://www.youtube.com/watch?feature=youtu.be&v=aQ2kYoMDw8E|title=The Truth About Ericcsonite|website=YouTube}}</ref>
Ericssonite is only found in the Langban mine in Sweden, associated with a metamorphic manganese orebody. Also it is always inter-grown with orthoericssonite, which is almost identical to ericssonite except it contains extra silicon and oxygen in its chemical formula.
==References== {{Reflist}}
Category:Barium minerals Category:Iron(III) minerals Category:Manganese(II) minerals Category:Sorosilicates Category:Monoclinic minerals Category:Minerals in space group 12
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