Banalsite
Banalsite is a rarely occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the crystal system of the chemical composition BaNa2 [ Al4Si4O16 ], thus forming the barium - analogue of the ( later discovered ) Stronalsits ( SrNa2 [ Al4Si4O16 ] ).
Banalsite only very rarely develops highly visible crystal faces. He usually can be found in the form of coarse -grained to massive mineral aggregates of white color and stroke color. The rare, shiny glass crystals are translucent and transparent in thin layers. Fresh cleavage surfaces show an iridescent pearly.
Special Features
Many Banal site show under short-to mid-wave UV light a yellow-green and under short-wave UV light, a faint bluish-white (very rare probably deep red ) fluorescence, which turns into a green phosphorescence after removal of the UV source.
Etymology and history
The name Banalsite is an acronym formed from the symbols of the chemical elements involved in the connection barium ( Ba), sodium ( Na), aluminum ( Al ) and silicon ( Si).
Was first discovered in the Banalsite " Benallt Mine" at Rhiw ( Llanfaelrhys ) on the Welsh Lleyn Peninsula and described in 1944 by W. Campbell Smith, FA Bannister and M.H. Hey.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Banalsite belonged to the mineral class of " silicates and Germanates " and there to the general ward of the " framework silicates ( tectosilicates ) " where he eponymous member of the anorthoclase anorthite Banalsite - series with the other members albite, andesine, anorthite, anorthoclase, Bytownite, Dmisteinbergit, Filatovit, labradorite, oligoclase, Stronalsit and Svyatoslavit within the large group of the feldspars is.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Banalsite also in the class of " silicates and Germanates ", There, however, in the new department of " framework silicates ( tectosilicates ) without zeolitic H2O " one. This department is also further divided according to the presence of other anions in the chemical formula, so that the mineral is found according to its composition in the subsection " framework silicates ( tectosilicates ) without additional anions ," where it only together with Stronalsit the unnamed group 9 forms. FA.60.
The classification of minerals according to Dana assigns the Banalsite in the class of " silicates and Germanates " and there in the department of " framework silicates with Al- Si lattice ". Here he is with Stronalsit, Lisetit and Svyatoslavit in the eponymous " Banalsitgruppe " with the system no. 76.01.06 found within the subdivision "With Al- Si lattice ".
Education and Locations
Banalsite forms in small veinlets within manganese ores and in lenses of metamorphic re-formed clays. There in paragenesis occurs among other Alleghanyite, barite, calcite, Jacobsite and tephroite.
Worldwide, Banalsite so far (as of 2010) are detected in 15 localities: In the Sierra de las Minas in Guatemala, and " Shiromaru Mine " on Honshu (Japan ), in Mikkelvik in the Norwegian municipality Karlsøy, in Zhidoiskii massif of the Irkutsk Oblast the Chibinen on the Kola Peninsula in Russia, on the fields of the Kalahari manganese and in the Pilansberg complex near Rustenburg in South Africa, in the Swedish mining community Långban and at the Santa Rita peak in the San Benito County ( California ) in the USA.
Crystal structure
Banalsite crystallizes in the orthorhombic space group with lattice parameters a = 8.54 Å; b = 10.01 Å and c = 16.79 Å and four formula units per unit cell.