14th International Congress for Applied Mineralogy (ICAM), Belgorod, Russia, 23 - 27 September 2019, pp.183-188
There are 6 semi-precious gemstones in Turkey that are the most significant in terms of abundance and authenticity. These include smoky quartz, blue chalcedony, chrysoprase (aka Senkaya emerald), diaspore (aka sultanite/zultanite), sepiolite (aka meerschaum/Eskisehirstone), and jet (aka Oltustone). The smoky quartz occurs in the south of Buyuk Menderes Basin within metamorphic rocks of the massif. Chalcedony occurrences are in Canakkale and Saricakaya (Eskisehir). Chrysoprase is acquired in Bursa, Alasehir (Manisa) as yellowish green in color, Biga (Canakkale), Sivrihisar (Eskisehir) and Senkaya (Erzurum) as dark green in color. Diaspore occurs in Milas (Mugla), Soke (Aydin), Tire (Izmir), Bolkardagi Gerdekkilise area and Saimbeyli (Adana). Sepiolite occurrences are limited to Kibriscik-Koroglu (Bolu), Eskisehir and Konya. Jet (aka Oltustone) occurs in Oltu area (Erzurum). These are the major varieties that has been used to produce both jewelry and ornamental objects among which the prayer beads are one of the most indispensable object of oriental cultures in particular. These are also considered to be the authentic gems of Turkey and exported as raw and processed in into many forms. As for the prayer beads, lightness, color, durability, hardness, and cost are the main criteria. Thus, the Oltustone has been the major source for decades. However, the Eskisehir stone and blue chalcedony are becoming popular as well.