GLASS-CERAMICS AS IMITATION OF GEMS. I. GEMOLOGICAL CHARACTERISTIC, COMPOSITION, PHYSICAL PROPERTIES

UDC 549 : 679.8
https://doi.org/10.15407/mineraljournal.39.03.032
O.A. Vyshnevskyi, V.M. Khomenko, O.O. Kosorukov, V.V. Ripenko, T.G. Kalinichenko
M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the NAS of Ukraine
34, Acad. Palladin Ave., Kyiv, Ukraine, 03142
E-mail: vyshnevskyy@i.ua
GLASS-CERAMICS AS IMITATION OF GEMS. I. GEMOLOGICAL CHARACTERISTIC, COMPOSITION, PHYSICAL PROPERTIES
Language: Russian
Mineralogical journal 2017, 39 (3): 32-42
Abstract: Jewellery industry became in recent years one of application of hi-tech glass-ceramics. The results of complex mineralogical research of six coloured samples of artificial materials produced by FORMICA GROUP and RUSGEMS (Russia) and used as imitations of gems are presented in the article. It was shown that studied materials have SiO2-Al2O3 basis that plays a role of amorphous matrix, where nanoparticles of synthetic and/or artificial crystalline phases are present. Such structure allows attributing them to glass-crystalline materials. Due to their gemological characteristics (N = 1.61—1.72, ρ = 2.91—3.98, dispersion of light ~0.015) the studied samples are visually very close to many natural precious minerals (emerald, tourmaline, amethyst, peridot and other), however have completely different chemical composition. It is presented by three types of the multicomponent systems: SiO2 + Al2O3 + ZrO2 + MgO ± REE2O3, SiO2 + Al2O3 + Y2O3 ± ZrO2 ± REE2O3 and SiO2 + Al2O3 + La2O3 ± ZrO2 ± REE2O3, where REE — Ce3+ and rare-earth chromophoric ions Nd3+, Pr3+ and Er3+. Using optical spectroscopy method, it was found that the variety of colour gamut of studied glass-ceramic samples was achieved by adding different combinations of REE ions as well as Cu2+ to their composition. In contrast to traditional gemstones, narrow structured absorption bands of ff-transitions in lanthanide ions Nd3+, Pr3+ and Er3+ are characteristic feature of optical spectra of most materials studied. For imitation of red and violet stones the additions of Nd3+ and Er3+ are used in different proportions, and for reproducing of colouring of yellow-green, green and blue gemstones — Pr3+ and Cu2+. Due to the use of variable associations of chromophoric ions and proportions between them, the studied glass-crystalline materials perfectly reproduce colour of natural minerals, but they are cardinally different from the latter by their colouring agents. Thus, spectroscopic parameters, along with optically isotropic character, at N = 1.61—1.72, are the basic distinctive signs of this class of imitations of gems. 
Keywords: glass-ceramics, gemstone imitation, gemological characteristic, chemical and phase composition, physical properties. 
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