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Category Sorosilicates
(repeating unit)
Crystal system Monoclinic
Crystal class Prismatic (2/m)
(same H-M symbol)
Space group C2/m
Unit cell a= 20.42, b= 7.03
c= 5.34 [Å], β= 95.5°; Z = 4
Color deep reddish black
Crystal habit Massive - uniformly indistinguishable crystals forming large masses
Cleavage perfect, perfect on (100) fair on (011)
Tenacity very brittle
Mohs scale hardness 4.5
Luster sub metallic
Streak brown
Diaphaneity Translucent to opaque
Density 4.21
Refractive index 1.802-1.891
Pleochroism x= pale greenish tan, y= red-brown, z= deep brown
Other characteristics weakly magnetic

Ericssonite has a general formula of BaMn2FeO[Si2O7](OH).[1] 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.[2] Ericssonite was discovered in the Jakobsberg Mine in Värmland, Sweden.[3]

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°.[4] 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.

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.


  1. ^
  2. ^ "Ericssonite Mineral Data". 
  3. ^ "Jakobsberg Mine, Nordmark, Filipstad, Värmland, Sweden". Mindat. 
  4. ^ 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.