A unique mineral of the pyrochlore supergroup from Baikal region (addition to its first description made by V. I. Vernadsky)

L. P. Rikhvanov, V. D. Strakhovenko, S. Z. Smirnov, Yu. D. Litasov , E. A. Kulinich.

Zapiski RMO (Proceedings of the Russian Mineralogical Society). 2018. V. 147. N 6. P. 75-89


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Language: Russian 


In the early 20th century, new radioactive mineral was found near the Baikal Lake. Academician Vladimir Vernadsky named it «mendeleevitå». Unfortunately this mineral was not characterized by the Russian scientists and name «mendeleevitå» was discredited because of the lack of modern accurate data for the approval of an independent mineral species. Any process of scientific knowledge requires deep and accurate information of the studied object or phenomenon in the place of its initial detection (holotype in mineralogy, rock type in petrography, etc). The veracity is required for perception of the historical background of the term «mendeleevitå», investigation of this mineral and, finally, determination  of position of this mineral in the modern mineralogical classification. The main aim of the study is to investigate the sample of historical highly radioactive mineral from the group of tantalum-niobates and to identify the place of «mendeleevitå» in the modern classification of minerals of pyrochlore supergroup. The methods used in the study are X-ray diffraction analysis, electron microscopy, energy dispersive spectroscopy, infrared spectroscopy, and thermal analysis. As a result, authors investigated the holotype of the «mendeleevitå». It was found that the mineral is isometric, highly radioactive and metamict. The crystal structure of «mendeleevit» is determined only after calcinations at the temperature of 800 °C. Elementary lattice parameters are 10.23—10.26 Å. This parameters correspond to the lower limit of value range for the group of pyrochlore-betafite. According to the modern mineralogical nomenclature, «mendeleevitå» can be determine as oxyuranobetafite from pyrochlore supergroup. «Mendeleevitå» does not include significant detectable quantity of thorium and rare earths.

Key words: radioactivity, radioactive minerals, Mendeleev, Baikal, Academician Vernadsky, pyrochlore supergroup, oxyuranobetafite.