Ericssonite has a general formula of BaMn₂FeO i₂O₇OH). It was discovered in 1967 and named after

John Ericsson John Ericsson (born Johan Ericsson; July 31, 1803 – March 8, 1889) was a Swedish-American inventor. He was active in England and the United States. Ericsson collaborated on the design of the railroad steam locomotive ''Novelty'', which com ...

(July 31, 1803 – March 8, 1889), a well known Swedish American inventor, engineer and designer of the iron-clad ship USS ''Monitor''. Ericssonite was discovered in the Jakobsberg Mine in Värmland, Sweden. Ericcsonite is

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

; this means it contains three unequal vectors, two of these vector angles are perpendicular while the other is at an angle greater than 90°. Optically ericssonite is anisotropic which means that the mineral has more than one

index of refraction In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, or ...

, 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 Manganese is a chemical element with the symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of industrial alloy use ...

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

Barium minerals Iron(III) minerals Manganese(II) minerals Sorosilicates Monoclinic minerals Minerals in space group 12 {{silicate-mineral-stub