Filipstadite

Filipstadite
General
Category Oxide mineral
Formula
(repeating unit)		 (Mn,Mg)(Sb5+0.5Fe3+0.5)O4
Strunz classification 4/B.05-70
Dana classification 7.2.13.1
Crystal system Isometric
Space group Fd-3m
Unit cell a=25.93 (approximated)
Identification
Color Black
Crystal habit modified (pseudo)octahedra
Crystal symmetry Isometric - Hexoctahedral (m3m)
Twinning Poor
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness 6-6.5
Luster Metallic
Streak Brown
Density 4.9 (calculated)
Optical properties Biaxal
References [1][2][3]

Filipstadite is a very rare mineral[3] of the spinel group, with the formula (Mn,Mg)(Sb5+0.5Fe3+0.5)O4.[4] It is isometric,[2] 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.[2] Filipstadite is chemically close to melanostibite.[5] The mineral comes from Långban, Sweden, a manganese skarn deposit famous for many rare minerals.[6]

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.[1]

Notes on crystal structure

Cations and anions in filipstadite occupy ⅛ of the octahedral and ½ 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 substites, 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.[2]

References

  1. 1 2 "Filipstadite - Handbook of Mineralogy" (PDF). Handbookofmineralogy.org. Retrieved 2016-03-12.
  2. 1 2 3 4 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
  3. 1 2 "Filipstadite: Filipstadite mineral information and data". Mindat.org. Retrieved 2016-03-05.
  4. ↑ 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.
  5. ↑ "Melanostibite: Melanostibite mineral information and data". Mindat.org. Retrieved 2016-03-10.
  6. ↑ "Långban, Filipstad, Värmland, Sweden - Mindat.org". Mindat.org. Retrieved 2016-03-10.


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