(Mn,Ca)₅(Mn,Fe,Sb)₂SiO₁₁

This sample of langbanite is displayed in the Smithsonian Museum of Natural History. Langbanite is a silicate mineral of antimony and manganese along with calcium and iron. It has the composition (Mn,Ca)₅(Mn,Fe,Sb)₂SiO₁₁. The sample at left is about 8 cm across and is from Langban mine, Filipstad, Varmland, Sweden. The black crystals are langbanite.