Mineralogical and structural characterization of zeolitic tuff from the Slanci deposit, Serbia

Abstract

Lake Miocene deposits located east of Belgrade in the Danube bend, around Veliko Selo and Slanci, are rich in zeolitic tuffs of the heulandite type. This paper presents mineralogical and structural investigations of zeolitic tuffs in which the dominant phase is Ca‐heulandite with a Si/Al ratio of 3.78. Volcanic glass and biogenic amorphous silica are present as accompanying components. Quantitative X‐ray powder analysis determined the following mineral composition: heulandite (85.1%), quartz (1.9%), muscovite (5.9%), albite (6.6%), orthoclase (0.6%) and calcite (0.21%). The structure was refined in the space group C2/m, with a disordered distribution of Al and Si within the tetrahedral framework. The following methods were applied: powder X‐ray diffraction on a polycrystalline sample (XRPD), scanning electron microscopy and energy-dispersive X‐ray spectroscopy (SEM/EDS), and differential thermal and thermogravimetric analysis (DTA/DTG/TG).