Acta Musei Moraviae

Mogánite – An unusual SiO₂ polymorph and its occurrence within the Czech and Slovak siliceous rocks

Mogánite is an interesting SiO₂ polymorph in the terms of structure, properties, distribution and potential scientific use. However, there is only very limited information about its presence or absence in silicites of Czech territory. A new study of the distribution of mogánite in selected Czech and Slovak microcrystalline SiO₂ materials was based on seventeen samples from the Bohemian Massif and its sedimentary cover (Permo-Carboniferous, Upper Jurassic, Upper Cretaceous, Cenozoic & samples of uncertain age and erratic material), seventeen samples from the Outer Western Carpathians and their sedimentary cover (Lower and Upper Cretaceous, Paleogene). Six silicites from central Slovakia were used as a comparative material. Silicites with a predominant or high proportion of mogánite were not found in the studied set. The highest proportions of mogánite (up to 35 wt.%) were found in some lacustrine silicites and flints. The prevailing low mogánite contents is related both to the usually high age of the samples and to their presumed genesis. The difficulties associated with the detection and precise quantification of mogánite content in silicites can be a significant complication, e.g. for the study of the provenance of archaeological artifacts.