Carpathian Journal of Earth and Environmental Sciences

Geological and mineralogical investigations were performed on sulfates and coexisting minerals from the Badenian Tyras’ka Formation, which is situated near Khodoriv (the Western Ukraine). The following varieties of sulfate rocks were put in evidence: massive, banded, layered, alabaster, veinlet and spotted, saber-like. Gypsum as major mineral as well as anhydrite and calcite as minor phases have been determined using microscopic and X-ray powder diffraction (PXRD) investigations. Microbeam analyses of different types of sulfate-bearing aggregates were performed in order to determine the differences between various generations of gypsum and to establish the order of crystallization. According to these studies, the differences in microstructures related to size and shape of gypsum crystals are: longer and plate crystals in sectors with massive structure, equi-granular within separate layers and spotted sectors, and needles shape in veinlets. In the study area, alabaster is represented by gypsum with high hardness (up to 131 kg/mm²) and occurs as massive, banded, layered, veinlet, spotted and saber-like. According to investigated relationships between gypsum and other minerals, the order of crystallization is: anhydrite – gypsum – calcite, celestine and quartz.