Braunite is a silicate mineral containing both di- and tri-valent manganese with the chemical formula: Mn<sup>2+</sup>Mn<sup>3+</sup><sub>6</sub>[O<sub>8</sub>|SiO<sub>4</sub>]. Common impurities include iron, calcium, boron, barium, titanium, aluminium, and magnesium.
Braunite forms grey/black tetragonal crystals and has a Mohs hardness of 6 â 6.5.
It was named after the Wilhelm von Braun (1790âÂÂ1872) of Gotha, Thuringia, Germany.
A calcium iron bearing variant, named braunite II (formula: Ca(Mn<sup>3+</sup>,Fe<sup>3+</sup>)<sub>14</sub>SiO<sub>24</sub>), was discovered and described in 1967 from Kalahari, Cape Province, South Africa.