Filipstadite is a very rare mineral of the spinel group, with the formula .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. It is isometric,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 although it was previously thought to be orthorhombic. When compared to a typical spinel, both the octahedral and tetrahedral sites are split due to cation ordering. Filipstadite is chemically close to melanostibite. The mineral comes from Långban, Sweden, a manganese skarn deposit famous for many rare minerals.
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.
Notes on crystal structure Cations and anions in filipstadite occupy of the octahedral and 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.
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