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1. Evaluation of garnet phenocrysts in volcanic rocks (Görece/İzmir – Western Türkiye) for their usability as a semi-precious gemstone by multi-analytical methods.

Author

Ören, Ufuk and Koralay, Tamer

Subjects
*GEMS & precious stones, *RARE earth metals, *VOLCANIC ash, tuff, etc., *PHENOCRYSTS, *GARNET, *RARE earth oxides, *DIAMONDS
Abstract

Garnets are observed as phenocrysts in blocky rhyolites of Cumaovası Volcanites and are reddish-blackish in color, show vitreous luster, and have dodecahedron forms varying between 0.5 and 2.0 cm in size. In optical microscope investigations, they exhibit fractured structures and contain quartz, hematite, chlorite, and acicular rutile inclusions. Garnet phenocrysts are highly consistent with spessartine-type garnet end members in the Raman spectrum. This result is supported by the mineral chemistry results determined as spessartine (Sps)0.50–0.52 almandine (Alm)0.47–0.48 grossular (Grs)0.01–0.02. In the chondrite, primitive mantle, and Mid-Oceanic Ridge Basalt normalized multi element variation diagrams, garnet phenocrysts show enrichment in all elements (except Sr, K, P, and Ti). In contrast, in the upper continental crust normalized multi element variation diagram, garnet phenocrysts show depletion in large ion lithophile elements (Rb, Ba, K, and Sr) relative to high field strength elements. They exhibit slight enrichment in light rare earth elements ((La/Sm)N = 0.11–1.07) relative to heavy rare earth elements ((Sm/Yb)N=0.78–0.97). Furthermore, garnet phenocrysts have significant negative europium (Eu) ((Eu/Eu*)N = 0.01–0.02) and mildly positive cerium ((Ce/Ce*)N = 2.43–13.77) anomalies indicating hot and reduced magma conditions. The Y/Ho ratios have ranged from 18.9 to 20.3 and are close to the chondrite value. The zircon saturation temperatures (TZr) of the garnet's host rock was determined to be 756 °C. As a result of mineralogical, geochemical and gemological studies, it was concluded that Görece garnet phenocrysts have glassy luster and semi-transparent dodecahedral crystal shapes, so they can be classified as semi-precious gemstones. In addition, the rare earth element content of the garnet phenocrysts is similar to that of industrial garnet sands and it is thought that they may have potential. [ABSTRACT FROM AUTHOR]

Published
2024
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3. INVESTIGATIONS ON MINERO-PETROGRAPHIC, SPECTROSCOPIC and GEMOLOGICAL PROPERTIES OF PYROXENE CRYSTALS IN PEGMATITE GABBRO.

Author

ÖREN, Ufuk, KORALAY, Tamer, DENİZ, Kıymet, and KADIOĞLU, Yusuf Kağan

Subjects
*GABBRO, *PYROXENE, *CRYSTAL surfaces, *CRYSTALS, *SPECIFIC gravity, *OLIVINE, *CHROMITE
Abstract

The ultramafic-mafic rocks in southwestern part of Turkey, are called as the Yeşilova ophiolite was firstly described by Sarp [1]. The Yeşilova ophiolite represents an ophiolite suite with missing row character and is comprised tectonites, followed upwards by ultramafic-mafic cumulates, gabbroic rocks, plagiogranite and basalt from the bottom to the top. The pegmatite gabbro is very minor lithology within the olivine gabbro and/or tectonite and formed in lenticular shaped or thin dike. They are greenish grey in color and have medium to coarse grained (2->5 mm) crystal size. Microscopically, pegmatite gabbros have sub-ophitic to ophitic texture and contain plagioclase, pyroxene, chlorite, epidotite, and ilmenite. This mineral composition is also supported by X-Ray Diffractometer. In addition, pyroxenes are diopside in composition, and has chiefly seven Raman peaks. The strong peaks are at 1011-1012; 662-666, and 322-325 cm-1. Four intense peaks are seen at 509-510; 389-393; 253, and 136 cm-1. In terms of EPMA results, pyroxenes vary from Wo41.72-49.63En44.99-49.83Fs5.39-8.53 in composition. They plot on the diopside region on the Wollastonite-Enstatite-Ferrosillite triangular diagram. According to pyroxene geothermobarometry by Putrika [2], crystallization of diopside took place at temperature of 1445.59 °C and pressure of 14.36 kbar. Some non-destructive gemological tests (specific gravity, refractive index, color, UV properties) were carried out on the polished pyroxene samples. The pyroxenes have specific gravity range from 2.87 and 3.01. R.I values of pyroxene have varying from 1.665 to 1.728. Diopside is light green, translucent, and has dull luster on the crystal surface. It characteristically displays an iridescent optical effect. Moreover, diopside showed purple fluorescence under UV rays but did not show phosphorescence. All mineralogic, spectroscopic, geochemical and gemological results indicate that there may be economic values of diopside crystals in pegmatite gabbro in case of single crystals with sufficient reserve. [ABSTRACT FROM AUTHOR]

Published
2019
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4. Gemmological and mineralogical investigations and genesis of the massive dark green chrysoprase from the Biga-Çanakkale region

Author

Ören, Ufuk, Hatipoğlu, Murat, and Doğal Yapı Taşları ve Süs Taşları Ana Bilim Dalı

Subjects
Trace elements, Luminescence, Jeoloji Mühendisliği, Çanakkale-Biga, Geological Engineering
Abstract

Her nekadar Türkiye'deki başlıca ticari krizopras yatakları, yaklaşık beş bölge içerisinde yani Çanakkale, Eskişehir, Bilecik, Erzurum ve Mardin, bulunsa bile, süstaşı kalitesindeki krizoprasın en önemli yatağı, Biga-Çanakkale bölgesinde yer almaktadır. Bu nedenle, mevcut çalışma, bir metamorfik kuşağın sınırı boyunca silisleşmiş serpantinitlerlerdeki ayrışmış bir kabukla örtülmüş çatlak dolgusu olarak bulunan Biga krizopras yatağı üzerine odaklanmıştır. Bunun bir sonucu olarak, Biga krizoprasının önceden yazılmamış çok sayıdaki karekteristikleri bu çalışma süresince ilk kez tanımlanmıştır. Biga krizopras örneklerinin bazıları, tipiksel renk ve kaliteyi göstermek için kabaşonlar ve dilimler halinde çok sayıda süstaşı objeleri olarak kesilmiş ve parlatılmıştır.Ortalama hacimsel (XRF) ve iz element (ICP-AES) kimyasal analizler ortaya çıkarmıştır ki, bazı iz elementlerin, örğ. Fe, Cr, Mn, As, Ni, Pb, Sb ve Zn göreceli yüksek konsantrasyonları, Biga krizoprası için karakteristiktir. Bu iz elementlerin birkaçı, Polonya'dan, Kazakistan'dan ve Tanzanya'dan elde edilen herhangi bir krizopras örneği içerisinde mevcut olabilir, ancak bunlardan bazıların konsantrasyonları sıra dışıdır.Biga krizopras örnekleri, saçınımsal konfokal mikro-Raman spectroskopisi (DCµRS) ve de diğer iyi bilinen analitiksel metotlar kullanarak karakterize etmek ve detaylı tanımlamak için incelenmişlerdir. Buna göre, 1577, 1430, 1303, 1160, 1082, 549, 501, 460, 394, 352, 259, 206, 139 ve 126 cm-1'lerde piklenmiş güçlü mikro-Raman bandları, Biga krizoprasının karakteristikleridir.Diğer yandan, Biga krizopras örnekleri çok sayıda geniş ve şiddetli lüminesans bandları gösterirler. Biga krizoprasının üç farklı lüminesans spektraları [fotolüminesans (PL), kathodolüminesans (CL) ve termolüminesans (TL)] göz önüne alınmış ve değerlendirilmiştir.Sonuç olarak, gemolojiksel, mineralojiksel ve spektroskopsal deliller, Biga krizoprasının coğrafik oluşum kökeniyle ilgili kesin ve olumlu tanımlamalar sağlarlar. Görülmektedir ki, elde edilen bu veriler bu cins krizopras süstaşı için özgün anahtar işaretler vermektedir. While the major commercial chrysoprase deposits in Turkey are present in about five different regions, namely Çanakkale, Eskişehir, Bilecik, Erzurum and Mardin, the most important deposit of gem-quality chrysoprase is located in the Biga?Çanakkale region. Therefore, the present study is focused on the Biga chrysoprase deposit, which is found as fracture fillings covered with a weathering crust in the silicified serpentinites throughout the border of a metamorphic zone. Several previously undocumented characteristics of Biga chrysoprase are described for the first time during this investigation. Some of the Biga chrysoprase samples have been cut and polished into cabochons and slabs as gem objects to show its typical color and quality.Average bulk (XRF) and trace element (ICP-AES) chemical analyses reveal relatively higher concentrations of some trace elements, such as Fe, Cr, Mn, As, Ni, Pb, Sb, and Zn are characteristics for Biga chrysoprase. Some of these elements can be found in any chrysoprase sample from Poland, Kazakhistan, Australia or Tanzania, even though the concentrations of some are unusual.In addition to other well-known analytical methods, Dispersive confocal micro-Raman spectroscopy (DCµRS), was used to characterize and identify in detail the Biga Chrysoprase samples. Accordingly, the strong micro-Raman bands that peaked at 1577, 1430, 1303, 1160, 1082, 549, 501, 460, 394, 352, 259, 206, 139 and 126 cm-1 are characteristics of Biga Chrysoprase.Biga chrysoprase samples also show numerous broad and intensive luminescence bands. Three different luminescence spectra of the Biga chrysoprase [photoluminescence (PL), cathodoluminescence (CL), and thermoluminescence (TL)] were taken into consideration, and evaluated.Finally, gemmological, mineralogical and spectroscopical data provide positive identification of the provenance of Biga chrysoprase. It can be seen that the these data provide a unique fingerprint for this kind of chrysoprase gem material. 76

Published
2012

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