@ARTICLE{Başibüyük_Zeynel_Surprise_2023,
 author={Başibüyük, Zeynel and Gürbüz, Meltem and Akbudak, Ilkay Kaydu},
 volume={vol. 39},
 number={No 1},
 journal={Gospodarka Surowcami Mineralnymi - Mineral Resources Management},
 pages={5-22},
 howpublished={online},
 year={2023},
 publisher={Komitet Zrównoważonej Gospodarki Surowcami Mineralnymi PAN},
 publisher={Instytut Gospodarki Surowcami Mineralnymi i Energią PAN},
 abstract={Almus agates which are forms of nodules like egg-shaped are located in the Eocene aged Almus volcanics in Tokat (Turkey). These nodules are surprise eggs in spherical or oval form ranging from a few cm to 25–30 cm. It is thought that the most effective reason for the formation of the magnificent texture and color combinations of the agates in the region is the iron element. In thin section studies, agate formations are composed of length-slow zebraic chalcedony and quart zine. In addition, curved fossil like structures composed of iron oxide minerals offer visual richness. The host rock in which the Almus agates are located is trachyte, which consists of sanidine, plagioclase microlites and small opaque minerals, in which microlithic porphyritic and flow (trachytic) texture are observed. As a result of the multipoint eds (field emission scanning electron microscope), it was determined that the quartz is composed of Si, O and Fe. The content of the iron element, which is thought to cause color, was observed in the range of ca 1–1.5 wt.%. According to XRF analysis results, in Almus agates, there is depletion of Fe2O3 content in fine crystalline regions (ca 1 wt.%) compared to coarse crystalline zones (ca 1.5 wt.%). In order to determine the usability of Almus agates as gemstone, various cabochon shapes were made in Ümit Ulus Gemstone Processing workshop. It has been observed that these agates can be used for both collection and gemstone purposes due to their unique patterns and color compensation.},
 type={Article},
 title={Surprise eggs, the miracle of nature: almus agates (Tokat - Turki̇ye)},
 URL={http://journals.pan.pl/Content/126714/PDF/Basibuyuk%20i%20inni.pdf},
 doi={10.24425/gsm.2023.144632},
 keywords={agate, gemstone, mineralogy, gemology, geochemistry},
}