Braunite

Braunite (also hard brown stone, Straight Klas, Heteroklin or Pesillit ) is a rarely occurring mineral from the mineral class of " silicate and germanate " [* ]. It crystallizes in the tetragonal crystal system having a chemical composition Mn2 Mn3 6 [ O8 | SiO4 ] and developed either dipyramidal striped by { 001 } and { 201 } crystal or granular mineral aggregates to moderate brownish black color.

With Abswurmbachit Braunite forms a complete mixed batch.

Etymology and history

Was first found Braunite 1826 Friedrichroda in the Thuringian Forest and described by Wilhelm Ritter von Haidinger, of the mineral in honor of the chamber Raths Braun of Gotha and named after this.

Classification

In the now outdated nomenclature of minerals by Strunz ( 8th edition ) of the Braunite still belongs to the general ward of the " island silicates with tetrahedral foreign anions ( Neso - Subsilikate ) " where he, along with Abswurmbachit, Franciscanit, Katoptrit, Långbanit, Neltnerit, Örebroit forms Welinit and Yeatmanit own group.

The revision of the Strunz'schen Mineral classification in the 9th edition of this department a separate group was divided according to the precise coordination of the cations involved and the mineral is now, only with Abswurmbachit, Neltnerit and Tranquillityit forming, in the subsection " island silicates with additional anions and cations in most cases and > coordination ".

The commonly used in English-speaking classification of minerals according to Dana assigns ( here Braunite - I) is not in the silicates, but with the oxides to a Braunite. He is there with Neltnerit, Braunite -II and Abswurmbachit the " Humitgruppe ( Tetragonal: I41/acd ) with Si " within the sub-division of " multiple oxides with the general formula ABX2 ".

Modifications and varieties

• Braunite - II is a calcium-containing variety.

Education and Locations

Braunite formed by metamorphism or weathering of manganese silicates and oxides. Accompanying minerals include pyrolusite, Jakobsit, hausmannite, bixbyite, rhodonite, spessartine and hematite.

So far Braunite in over 300 localities (as of 2009) are detected, including Australia, Belgium, Chile, China, Germany, France, Greece, Great Britain, India, Indonesia, Ireland, Italy, Japan, Kazakhstan, Madagascar, Morocco, Macedonia, Mexico, New Zealand, Norway, Oman, Austria, Pakistan, Poland, Portugal, Russia, Sweden, Switzerland, Slovakia, Spain, South Africa, South Korea, Czech Republic, Turkey, Ukraine and the USA.

Crystal structure

Braunite crystallized tetragonal in the space group with the lattice parameters a = 9.41 Å and c = 18.67 Å, and eight formula units per unit cell.

Use

Braunite is used at local enrichment as manganese ore.