Abswurmbachite
- IMA 1990-007
The mineral Abswurmbachit is a very rarely occurring silicate from the island Braunitgruppe with the chemical composition Cu2 MN63 [ O8 | SiO4 ]. It crystallizes in the tetragonal crystal system and has so far been found only in the form of microcrystalline, black particles of about 50 micron size.
Abswurmbachit forms with Braunite a complete mixed batch.
Etymology and history
Was first found in Abswurmbachit Apoikia and Myli ( Evia ), Greece. Analyzed and described the mineral was by Thomas Reinecke, Ekkehart Tillmanns and Heinz -Jürgen Bernhardt, which in recognition of their contributions to the crystal chemistry, the stability relations and physical properties of Braunite after the German mineralogist Irmgard Abs - Wurmsbach ( b. 1938 ), daughter of zoologist Hermann Wurmsbach, named. Since material was used from two Greek localities for analysis, both are also regarded as type locality.
Was recognized as an independent mineral Abswurmbachit 1990 by the International Mineralogical Association (IMA ) under the number IMA1990 - 007th The test results and the recognized name were published a year later in the science magazine " New Year book of Mineralogy " ( Dep: 163).
Type material of the mineral is preserved in the Smithsonian Institution in Washington DC as well as at the Institute of Mineralogy, Geology and Geophysics, Ruhr- University Bochum.
Classification
In the now outdated but still in use classification of minerals according to Strunz ( 8th edition ) of the Abswurmbachit belonged to the mineral class of " silicates and Germanates " and there to the general ward of the " island silicates with tetrahedral foreign anions ( Neso - Subsilikate ) ", where he with braunite, Franciscanit, Katoptrit, Långbanit, Neltnerit, Örebroit, Welinit and Yeatmanit the unnamed group VIII/B.09 formed.
The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Abswurmbachit also included in the category of " silicates and Germanates " and then in the Department of the " island silicates ( nesosilicates ) ". This division, however, is further subdivided according to the possible presence of other anions and the coordination of the cations involved, so that the mineral according to its composition in the subdivision of " island silicates with additional anions; Cations " is to find where it together with Braunite, Braunite II Neltnerit and the " in most cases and > coordination. Braunite group "with the System No. 9.AG.05 forms.
In contrast to the Strunz 's classifications predominantly common in English-speaking classification of minerals according to Dana assigns the Abswurmbachit in the class of " oxides and hydroxides " one. Here he is with Braunite -I, -II and Braunite Neltnerit in the " Humitgruppe ( Tetragonal: I41/acd ) with Si " with the system no. 07:05:01 found within the sub-division of " multiple oxides with the formula ABX2 ".
Modifications and varieties
There is a continuous series of solid solutions, in which copper is gradually replaced by manganese intermediate Abswurmbachit and Braunite. Another similar mineral is the Neltnerit which contains copper instead of calcium. However Between Abswurmbachit and Neltnerit probably a miscibility gap, so that no solid solution is possible.
Education and Locations
Abswurmbachit forms together with Braunite in manganese - and aluminum-containing piemontite - Sursassit - quartzites at pressures of 7-11 kbar and temperatures of 300-420 ° C. Other accompanying minerals include Ardennite, hollandite, clinochlore, quartz, rutile and Shattuckit.
In addition to its type localities in Greece Abswurmbachit was still in Japan Iyomishima (now Shikokuchuo ) are found.
Crystal structure
Abswurmbachit crystallized tetragonal in the space group I41/acd with the lattice parameters a = 9.41 Å and c = 18.55 Å, and eight formula units per unit cell.