The determination of mineralogic, petrographic, spectroscopic, geochemical and gemological properties of garnets selected from Turkey

Garnet crystals which are located at different locations of Turkey (Karacasu, Çine/Aydın, Kayaağıl/Uşak, Menderes/İzmir, Susurluk/Balıkesir, Ekinözü/Kahramanmaraş, Doğanşehir/Malatya) were investigated in detail. Garnet crystals in Karacasu, Çine, Kayaağıl and Ekinözü locations were observed as porphyroblasts in metamorphic rocks and they were determined in almandine compositions. Garnet crystals in Susurluk lower and upper zone, and in Çavuşlu location were formed in skarn zones of limestone-granitoid contact and they have composition of andradite and Almandine. Garnets in Hudutköy are seen as rounded crystals in amphibolite rocks and have the composition of Almandine. Garnet crystals in Menderes location were in phenocrystals forms in rhyolite and in the composition of spessartine. XRD and Confocal Raman Spectrometry investigations also support the results which were obtained through mineral chemistry. According to geochemical analysis results it was determined that (La/Sm) rates of garnet crystals change between 0.11 (Görece) and 15.91 (Çavuşlu), (Sm/Yb)N rates change between 0.16 (Susurluk Lower) and 5.29 (Susurluk Upper), (Eu/Eu*)N rates change between 0.01 (Görece) and 5.44 (Çavuşlu), (Y/Ho)N rates change between 0.66 (Görece) and 2.09 (Çavuşlu), and Sc contents change between 1 ppm (Susurluk Lower-Upper, Çavuşlu) and 82 ppm (Görece). It was evaluated in line with the geothermobarometer calculations that garnet crystals occur at the pressures between 3.08 (Ekinözü) and 8.07 (Kayaağıl) kbar and at the temperatures between 465 (Ekinözü) and 799 (Susurluk Lower-Upper) °C. According to Rare Earth Element contents, garnet porphyroblasts in metamorphic rocks in Karacasu, Çine, Ekinözü locations display slight enrichment (Karacasu ∑NTE: 345.74-412.37, Çine ∑NTE: 192.2-212.1, Ekinözü ∑NTE: 162.07-284.89). According to the results of nondestructive gemological tests (specific gravity, refractive index, optical absorption, UV properties, color properties, SEM analysis), it was revealed that since garnets in Karacasu, Görece, Susurluk Lower-Upper, Maraş and Çavuşlu are low/limited, whereas garnets in Çine, Kayaağıl and Hudutköy are altered and they do not have the potential to be gemstones.