Mineralogical-Petrographical and Gemological Properties of Chalcedony Occurences of Tokat-Artova Region

Abstract

The study area is located around Gümüşyurt and Bayırlı Villages in Tokat/Artova city. Permian aged amphibolite rocks are formed the basement in the region. In the upper part of this unit Silurian aged, grey-beige in color and recrystallized limestone is found. There are mainly metamorphic units of Permian aged metaclastics, metamorphic rocks having metabasic origin suh as chlorideschist, glaucophaneschist, micaschist and amphibolite composition and white, cream, beige, blackish gray colored, hard and brittle, recrystallized and partially silicified limestone blocks forms the basement of the region.The ophiolithic rocks from Late Jurassic to Early Cretaceous in age show a wide range distrubution in South part of the study area. Eocene limestone /conglomerates unit and Pliocene conglomerates unconformably overlaid to all previous units. Chalcedony samples, mostly in green color, occured in the small part of the Eocene aged limestone. Different green tones of chalcedony samples can be seen in different part of the study area. Even if dark brown to grey color tones of chalcedony samples appaer as lower quality and transparency, all of the samples have enough quality to make earring, necklace, ring and prayer beads. According to field observations, Raman spectroscopy, GemmoFtir (Fouirer Transform Infrared Spektrofotometre for Gemology), geochemical analyses and standart gemologic tests, different tones of green samples identified as “Chromium Chalcedony”, dark brown to grey colored samples identified as “Common Chalcedony”.