A structural study on szaibelyte from its type-locality (Rézbánya, Bihar mts., Rumania)
Original szaibelyite Mg2(0H)[B20.)(0H)] material from its type-locality (Rézbánya, Bihar Mts., Rumania) has been investigated. Starting with an XPD ab initio determination, its unit cell was refined to the values of a=12.571(l), 6=10.4025(9), c=3.1333(4) Á and p=95°54.2(9)' in P2,/a symmetry. T...
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| Format: | Article |
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University of Szeged, Department of Mineralogy, Geochemistry and Petrology
Szeged
1997
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| Series: | Acta mineralogica-petrographica
38 |
| Kulcsszavak: | Kőzettan, Ásványtan, Földtan |
| Subjects: | |
| Online Access: | http://acta.bibl.u-szeged.hu/24861 |
| Summary: | Original szaibelyite Mg2(0H)[B20.)(0H)] material from its type-locality (Rézbánya, Bihar Mts., Rumania) has been investigated. Starting with an XPD ab initio determination, its unit cell was refined to the values of a=12.571(l), 6=10.4025(9), c=3.1333(4) Á and p=95°54.2(9)' in P2,/a symmetry. The crystal structure was refined by Rietveld method on the basis of TAKÉUCHI'S (1973) model. The results converged to an atomic arrangement similar to the one determined for a szaibelyite sample from Königshall-Hindenburg, Germany. A search to find traces of an orthorhombic polytype in the XPD pattern, due to the 2| pseudosymmetry, failed to identify any. Neither was successful the attempt to find significant differences between the szaibelyite and a sample called 'ascharite' from Stassfiirt. TEM investigations revealed, that the [001] elongated crystallites of szaibelyite occur in bundles in which the individual fibres are randomly oriented around their c axis. Its most characteristic real structural feature is the (100) twinning producing weak diffuse scattering parallel to the a* axis in the SAED patterns. No polytype modifications or periodic twinning of the basic crystal structure were observed in the material. These results confirm the priority of the original description of szaibelyite (PETERS, 1861). In spite of the low accuracy of the early chemical analysis, the original description proved to be valid and in good accordance with the recent results. |
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| Physical Description: | 89-99 |
| ISSN: | 0365-8066 |