Filipstadite

Filipstadite is a very rare mineral[4] of the spinel group, with the formula (Mn,Mg)(Sb5+0.5Fe3+0.5)O4.[5] It is isometric,[3] although it was previously though to be orthorhombic. When compared to a typical spinel, both the octahedral and tetrahedral sites are split due to cation ordering.[3] Filipstadite is chemically close to melanostibite.[6] The mineral comes from Långban, Sweden, a manganese skarn deposit famous for many rare minerals.[7]

Filipstadite
General
CategoryOxide mineral
Formula
(repeating unit)		(Mn,Mg)(Sb5+0.5Fe3+0.5)O4
IMA symbolFps[1]
Strunz classification4.BB.05 (10 ed)
4/B.05-70 (8 ed)
Dana classification7.2.13.1
Crystal systemIsometric
Crystal classHexoctahedral (m3m)
H–M Symbol (4/m 3 2/m)
Space groupFd3m
Unit cella = 25.93 Å (approximated); Z = 216
Identification
ColorBlack
Crystal habitmodified (pseudo)octahedra
TwinningPoor
FractureConchoidal
TenacityBrittle
Mohs scale hardness6-6.5
LusterMetallic
StreakBrown
Density4.9 (calculated)
Optical propertiesBiaxal
References[2][3][4]

Occurrence and association

In the metamorphic Fe-Mn ore bodies of the Långban-type filipstadite associates with native antimony, calcite, native copper, forsterite, hausmannite, hedyphane, ingersonite, jacobsite, phlogopite, and svabite.[2]

Notes on crystal structure

Cations and anions in filipstadite occupy 1⁄8 of the octahedral and 1⁄2 of the tetrahedral holes of the spinel-type oxygen lattice, that has cubic close-packing. Tetrahedral sites are split into 5, and octahedral into 6 substitutes, due to cation ordering, which also causes the unit cell edge to be tripled. Antimony, most of magnesium and trace aluminium are located on the octahedral (M) sites, trace magnesium, zinc and silicon are on the tetrahedral (T) sites. Manganese and iron are on both M and T sites.[3]

References
  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. "Filipstadite - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-12.
  3. Bonazzi, P., Chelazzi, L., and Bindi, L., 2013. Superstructure, crystal chemistry, and cation distribution in filipstadite, a Sb5+-bearing, spinel-related mineral. American Mineralogist 98, 361-366
  4. "Filipstadite: Filipstadite mineral information and data". Mindat.org. Retrieved 2016-03-05.
  5. Dunn, P.J., Peacor, D.R., Criddle, A.J., and Stanley, C.J., 1988. Filipstadite, a new Mn-Fe3+-Sb derivative of spinel, from Långban, Sweden. American Mineralogist 73, 413-419.
  6. "Melanostibite: Melanostibite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  7. "Långban, Filipstad, Värmland, Sweden - Mindat.org". Mindat.org. Retrieved 2016-03-10.


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