Abstract: The study area is located within the borders of Tokat province, which is one of the richest provinces inTurkey in terms of gemstone diversity. The region contains various high quality gemstone formations, such as jasper,opal, chalcedony, agate, and chrysoprase, which have both geological and commercial value.Metamorphic, magmatic, and sedimentary units from the Paleozoic to the present day crop out in the studyarea. While Paleozoic-Mesozoic Tokat metamorphics and Artova ophiolite mélange form the basement, the Almusformation, which is represented by Lower Miocene aged volcano-sedimentary rocks from the central parts of thearea to the east, covers these units unconformably. Quaternary slope debris and alluviums in the Yeşilırmak basinare the youngest units in the region. The chalcedony formations are observed along an E-W trending almost vertically dipping fault zone passingthrough the north of Döllük and Korucak villages within the metamorphic units of the Tokat Massif. The chalcedoniesare in the cracks, fractures and cavities of the recrystallized limestones that exhibit a fractured and brecciatedstructure along a line of approximately 25 m in the direction perpendicular to this fault zone.In our mineralogical, petrographic, and gemological studies, quartz, tridymite, cristobalite, calcite and dolomiteswere determined, together with chalcedony. Chalcedonies have an average of 96.3% SiO2, 1.96% Fe2O3, 0.56%MgO, 1.02% CaO, 780 ppm Cr2O3, 6.3 ppm Cu, 20 ppm Hg, 4.2 ppm Pb, 18 ppm Ni and 77 ppm Zn. Chalcedonyformations are the last product of a hydrothermal system related to volcanic activities after the formation of the wallrocks. The movement of chalcedony-generating solutions within the fault zone and their inclusion of carbonate wallrock and secondary calcite formations during chalcedony formation ensured that the CaO and MgO content of thechalcedony was relatively high.