Gemological and mineralogical-petrographic study of the Eastern Sayan serpentinites

The purpose of the research is to study the mineralogical and petrographic characteristics of the Eastern Sayan serpentinites in order to identify their most decorative varieties. The objects of the study are the samples of serpentinites from the Ulan-Khodinskoye and Khokhurtovskoye deposits of the Eastern Sayan. Six samples were studied macroscopically then polished plates were made from them for gemological examination and thin sections for microscopic examination. All studies were carried out using standard gemological methods at the Gemmology Research Laboratory of the Irkutsk National Research Technical University. The petrographic study of thin sections was carried out using an Axio Lab A1 microscope. Macroscopically, two main ornamental varieties of serpentinite were identified: spotted bluish-green serpentinite and massive serpentinite of the color from dark green to black. The spotted structure of serpentinite is determined by numerous inclusions of ore minerals including magnetite and iron oxides. Its hardness is 4.5 on the Moh’s scale, its gloss is matte. The data on the main gemological characteristics of the samples corresponding to the results of already published studies of gem-quality serpentinites from other deposits were also obtained. Having analyzed the microstructure and mineral composition of the Eastern Sayan serpentinites, their correspondence to the spotty and massive decorative varieties of serpentinites from other Russian deposits was revealed. At the moment, this material is not duly appreciated, although it may well be used as a sculptural and jewelry-ornamental decorative stone.