Glauconitic Materials from Lower Miocene Macelj-Sandstones of the Hrvatsko Zagorje, North-Western Croatia

Abstract

The Lower Miocene Macelj sandstones from the western part ofHrvatsko Zagorje, are green in colour with variable amounts o f glauconitic grains. This paper presents the results of mineralogical andsome petrological analysis of three charactersitic samples of thesesandslones.The natural sandstone samples were analysed by polarisingmicroscope and by X -ray poweled diffraction (XRD). After separation,the pure or almost pure glauconitic materials were analysed by XRD,chemical analysis and thermal analysis (TG, DTA and DTG). Theresults show variation, not only in the glauconitic material of thesandstone samples, but also within individual samples. The amount ofsmeclite layers varies from < 5% to approximately 40% de pending onthe degree of order and the stage of glauconitic evolution. This is indicatedby the contents o f K, AI, Fe , adsorbed water and cation exchange capacity as well as XRD powder patterns.