braunite


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braunite

A magnesium silicate with various metallic impurities.
References in periodicals archive ?
Braunite forms the main part of the manganese ore in all the Val Graveglia mines, as layers within chert and as large masses up to 20 meters in thickness.
Braunite [Mn.sup.2+][[Mn.sup.3+].sub.6][SiO.sub.12]
Mineralogical composition of the fines at Balaghat and Ukwa mines is similar in nature and consists of Hollandite, Braunite, Psilomelane, Hematite, Apatite and Quartz.
Until 1828, mineralogists customarily used the term "prismatoidal manganese ore" for manganite (Mohs, 1825; Haidinger, 1826)--considering it among other black manganese species including "pyramidal manganese ore" (hausmannite), "brachytypous manganese ore" (braunite), "prismatic manganese ore" (pyrolusite) and "uncleavable manganese ore" ("psilomelane," now discredited in favor of cryptomelane).
Braunite occurs in good crystals in the manganese deposit at Ohrenstock near Ilmenau, in the Thuringian Forest about 100 km south of Ilfeld, but in the Ilfeld manganese veins it did not form good macrospecimens--lustrous crystals to 5 mm have been noted rarely, and braunite pseudomorphs after manganite occasionally have appeared (www.manganit.de, 2010).
The mineralogical studies of Bajaur Agency manganese deposits revealed the presence of Mn oxide and Mn silicate minerals comprising of Hausmannite and Braunite respectively.
Most of the spots showed the presence of Hausmannite and Braunite (Figs.
Occurrence: In manganese ore consisting of braunite, rhodonite, spessartine, tinzenite, parsettensite, sursassite and strontian piemontite in radiolarites.
Associated minerals are: braunite, quartz, the "violan" variety of diopside-aegirine-jadeite, strontiopiemontite, hollandite, cryptomelane, jadeite, antimony-bearing titanite and arsenic-bearing titanite and arsenic-bearing fluorapatite.
Also found at the Wessels at the same time was braunite in small (never more than 5 mm) but sharp, brilliant black bipyramidal crystals, with calcite.
The matrix of the philolithite-bearing fissures is a calcite-rich Mn oxide ore, dominated by braunite with lesser amounts of hausmannite.
Occurrence: In a matrix consisting primarily of braunite, sugilite and hausmannite, cut by pectolite veinlets (0.1-1 mm wide) in which the mineral occurs.