Crystal-chemical features of glauconite of Yangyssko-Bayguskarovskaya zone (Bashkortostan)

The results of mineralogical investigation of glauconite from the Yangyssko-Bayguskarovskaya zone (Bashkortostan) have been presented. Grains were studied by the complex of chemical and physical methods: X-ray diffraction, 57Fe Mössbauer spectroscopy, scanning electron microscopy and microprobe analyses. Special attention was given to the crystal-chemical features of mineral and processes of glauconite formation. Glauconite was characterized by a relatively high content of K, Fe, Mg. Content of total iron and potassium displayed a direct correlation (k=0.87). According to Mössbauer spectroscopy data Fe2+ occupied not more than 3% of the total iron content in glauconite. Average crystal-chemical composition of mineral was Ca0.04K0.49 [Fe3+1.05Fe2+0.04Al0.50Mg0.43] {(Si3.80Al0.16Fe3+0.04)4O10}(OH)2 and corresponded to evolved (less mature to mature) glauconite. Glauconite contained a small (