Braunite - Encyclopedia

    Class : Silicates
    Subclass : Nesosilicates
    Crystal system : Tetragonal
    Chemistry : Mn₇SiO₁₂
    Rarity : Common

Braunite is a notable component of large sedimentary manganese deposits (India, South Africa, etc.), especially abundant when they have undergone slight metamorphism. It is associated with a procession of manganese oxides and hydroxides (manganite, pyrolusite, psilomelane). This manganese silicate is also found in manganiferous contact deposits and in hydrothermal veins. It owes its name to Kammerrath Braun who provided the type sample. Braunite forms small, almost regular octahedra, exceptionally reaching 5 cm, often with striated truncations. In manganese deposits, it more often occurs in grainy masses made up of myriads of microscopic patches. It is a dark, brownish-black to steel-grey mineral with a strong metallic luster. It is an important manganese ore.

Main photo : Braunite on amphibole from Caspar Quarry, Ettringen, Germany © Volker Betz

A twin is known on {112}, producing a small re-entrant angle on {011}.

No fake inventories for this mineral species.