Filipstadite, (Mn,Mg)2(Sb0.55+Fe0.53+)O4 is a new mineral, related to spinel, from Långban, Värmland, Sweden. Filipstadite is orthorhombic, pseudocubic, with A = 8.640 Å for its cubic subcell. The strongest reflections in the X-ray powder pattern are [d (I/I0) (hkl)] 2.56 (100) (311), 1.527 (70) (440), 1.662 (60) (511), and 2.157 (40) (400). Filipstadite is black and occurs as equant crystals intimately associated with ingersonite, jacobsite, and calcite. In polished section (∼3200 K) it is gray, and for illuminant C, depending on composition, Y varies from 11.4 to 12.3%, λd from 473 to 475 nm and Pe from 2.3 to 3.3%. It is weakly anisotropic with poorly developed sector twinning.

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