Braunite


Also found in: Dictionary, Medical, Wikipedia.

braunite

[′brau̇‚nīt]
(mineralogy)
3Mn2O3·MnSiO3 Brittle mineral that forms tetragonal crystals; commonly found as steel-gray or brown-black masses in the United States, Europe, and South America; it is an ore of manganese.

Braunite

 

(after the 19th-century German scientist M. Braun), a mineral of the group of compound oxides. Its chemical composition is complex and is expressed approximately by the formula Mn2+Mn63+SiO12. It crystallizes in a tetragonal system, forming crystals of dipyramidal habit. It is most often found in the form of compact, granular aggregates. The color is black; the luster is matte and semimetallic. Braunite’s hardness on the mineralogical scale is 6.0-6.5; its density is 4, 700-5, 000 kg/m3. It is sometimes weakly magnetic.

Braunite is found in hydrothermal veins and in contact-metamorphic formations. The largest ore beds are in regionally metamorphized and contact-metamorphized sedimentary deposits that are rich in manganic oxides. Braunite is unstable and is easily converted to psilomelane and pyrolusite. Braunite is one of the most important manganese ores used for extracting ferromanganese. The largest deposits of braunite are in India; in the USSR it is found in Kazakhstan.

Mentioned in ?
References in periodicals archive ?
The same stratigraphic basal unit of the Monte Alpe Formation also includes the main manganese orebody, formed by braunite layers (Burckhardt and Falini, 1956).
No significant mineral finds have been reported from those localities, except for braunite and manganese oxides.
It must be remembered that most of the orebody consists of massive braunite, and the minerals hosted in veins and cavities can be recovered much more easily from the broken ore brought out of the mine rather than in situ.
Tabular, black and very lustrous crystals were found at the Gambatesa mine in the fractures in braunite and at the Molinello mine in vugs in rhodonite veins (Palenzona, 1987), at the same time that tangeite was collected.
The specimens from the Molinello mine, with crystals up to 1 cm, in rhodonite cavities or in the quartz veins that cut the braunite ore, are the best in the world.
It occurred very sparingly at the surface of cavities and fractures in a manganese ore containing tephroite, bementite, braunite, hausmannite and hematite.
Zeolite crystals visually identifiable as phillipsite or harmotome are well-known as last-formed minerals in carbonate veins, braunite fractures and tinzenite druses (Antofilli et al., 1983).
It is rarely found in crystals and can easily be misidentified as braunite. A close examination of the color can be a clue: usually hausmannite is dark brown while braunite is black.
With Ohrenstock/Ilmenau (see above under Braunite), Ilfeld is the type locality for hausmannite, described in 1813 and named for J.
The manganese ore species of the veins are braunite, hausmannite, cryptomelane, "wad" and most commonly, and of greatest economic significance, pyrolusite and manganite.
These studies revealed the composition of Hausmannite and Braunite as major manganese minerals(Table-1).
Besides Hausmannite Braunite occurs in these samples and can be distinguished from the former by the presence of birefringence and pleochroism.