About the finds of fougerite group minerals in the freshwater lakes of the Ilmensky reserve (South Urals)

Fougerite group minerals Fe 2+6(1-х)Fe 3+6xO 12H 2(7-3x)CO 3×3H 2O from the bottom sediments of the freshwater lakes Tatkul' and Bol'shoe Miassovo of the Ilmensky Reserve (South Urals) are shortly characterized. Their localization and diagnostic properties are described. It is shown that a Fe2+ phase closed to uncarbonate hydroxide-fuogerite or to synthetic compound Fe2+6(OH)10(H2O)2CO3×3H2O is presenttd in the lacustrine marls of the Lake Tatkul together with mossbauerite and trebeurdenite.