Enhancement of raw semi-precious gemstones as a special type of processing of nonmetallic mineral resources

Raw semi-precious gemstones, widely used in the jewelry industry, undergo certain stages of processing as ore mineral resources. These stages are cutting, power-tool treatment, chemical etching, etc. However, the most important stage of raw semi-precious gemstone treatment is enhancement–in the authors’ opinion, this is a special form of processing of nonmetallics, aimed at their appreciation and at improvement of their qualities and running characteristics. An example of such approach is the sequential thermal treatment of brown chromiferous andradites in the oxidizing (duration of 45–60 min, T of 760 °С, heating rate of 6–10 °С/min) and reducing (duration of 120 min, T of 820 °С, heating rate of 6–10 °С/min) media. Such treatment allows producing demantoid garnets of almost standard green color saturation owing to suppression of color centers Ti3+ and enhancement of Cr3+, thereby raising the cost of the initial material by hundreds of times. Alongside with this example, the article describes the other types of treatment such as soaking of porous turquoise and radiation of fade-colored sapphires, which also can be assumed as the special types of processing of nonmetallic minerals. In this fashion, treatment of the initial raw semi-special gemstones using different methods of improvement enhances decorative and running characteristics of the material, and raises its cost. From this point of view, enhancement offers process solutions in the field of treatment of raw semi-precious gemstones and can be a special type of their processing.

Akhmetshin E. A., Klimkin I. A., Plechov P. Yu., Petrova O. B. Enhancement of raw semi-precious gemstones as a special type of processing of nonmetallic mineral resources . MIAB. Mining Inf. Anal. Bull. 2025;(6):21-39. [In Russ]. DOI: 10.25018/0236_1493_2025_6_0_21.

E.A. Akhmetshin¹, Senior Lecturer, e-mail: 4966945@mail.ru,
I.A. Klimkin^1,2, Graduate Student; Museum Keeper, e-mail: klimkin.ivan.aleksandrovich@gmail.com,
P.Yu. Plechov², Dr. Sci. (Geol. Mineral.), Professor of the Russian Academy of Sciences, Director, e-mail: pplechov@gmail.com,
O.B. Petrova¹, Dr. Sci. (Chem.), Professor, e-mail: petrova.o.b@muctr.ru, ORCID ID: 0000-0001-7828-1058,
¹ D.I. Mendeleev Russian University of Chemical Technology, 125480, Moscow, Russia,
² A.E. Fersman Mineralogical Museum of the Russian Academy of Sciences, 119071, Moscow, Russia.

I.A. Klimkin, e-mail: klimkin.ivan.aleksandrovich@gmail.com.

1. Hermogenov N. N., Burnakova D. V., Lubyagina Yu. V., Dremina A. V., Popova M. N. Mineral enrichment. Vestnik Nauki. 2018, vol. 3, no. 7 (7), pp. 75—79. [In Russ].

2. Kurochkina A. S. Chemical ore beneficiation methods. Kholodnaya nauka. 2024, no. 3, pp. 59—66. [In Russ].

3. Babina S. A., Demina A. A., Yanina T. I., Gumenny A. S. Physical processes in the enrichment of minerals. Sbornik materialov X Vserossiyskoy nauchno-prakticheskoy konferentsii molodykh uchenykh s mezhdunarodnym uchastiem «Rossiya molodaya» [Collection of materials of the X All-Russian scientific and practical conference of young scientists with international participation «Young Russia»], Kemerovo, 2018, pp. 75102-1—75102-5. [In Russ].

4. Dyadin V. I., Latkin A. S. Enrichment of non-magnetic dispersed mixtures by electromagnetic methods. Fiziko-tekhnicheskie problemy razrabotki poleznykh iskopaemykh. 2004, no. 2, pp. 100—104. [In Russ].

5. Nepomnyashchikh A. I., Zhaboedov A. P., Volkova M. G., Fedorov A. M., Yashin V. N. Combined technology of enrichment of quartzites of the Eastern Sayan. Fiziko-tekhnicheskie problemy razrabotki poleznykh iskopaemykh. 2019, no. 3, pp. 113—121. [In Russ]. DOI: 10.15372/FTPRPI 20190314.

6. Semenov V. B. Chapter 8. Emerald in the production cycle of beryl mining and enrichment of the State Mining and Metallurgical Combine: loss of positions. 1931–1951. Uralian Geological Journal. 2002, no. 2 (26), pp. 157—171. [In Russ].

7. Rogachevskaya A. V., Akhmetshin E. A. Modification of low quality turquoise by impregnation on the example of Teghut deposit turquoise. Aktual'nye problemy nedropol'zovaniya. Tezisy dokladov XIX Vserossiyskoy konferentsii-konkursa studentov i aspirantov [Actual problems of subsurface use. Abstracts of the XIX All-Russian Conference-competition of students and postgraduates], vol. 2, SaintPetersburg, 2021, pp. 208—213. [In Russ].

8. Aleksandrova A. Yu., Ivanova L. A. Ornamental charoite treatment. Proceedings of the Siberian Department of the Russian Academy of Natural Sciences. Geology, Prospecting and Exploration of Ore Deposits. 2015, no. 3 (52), pp. 86—94. [In Russ].

9. Jaliya R. G. C., Dharmaratna P. G. R., Wijesekara K. B. Colour development of geuda stones after the gas-fired and electrically operated furnace heat treatments. Journal of Applied Toxicology. 2020, vol. 1, no. 1, pp. 46—51.

10. Thennakoon Gamage Ramesh, Ramawickrama G. Chamal Jaliya, Iillangasinghe Kalukumara M. S. C. Kumara Illangasinghe, Kuruppu Arachchige D. D. Nimanthika Kuruppu. Identification of the effect of localization on the colour alteration of «geuda» gemstones through the heat treatment Using ED-XRF, FTIR, and UV-Vis spectroscopic analysis. International Journal of Earth Sciences Knowledge and Applications. 2023, vol. 5, no. 3, pp. 324—332.

11. Vasenina R. R., Ismagilova A. I., Vasenin I. V. Enhancing methods of jewelry stones. Herald of technological university. 2015, vol. 18, no. 2, pp. 263—266. [In Russ].

12. Pshenichny M. I. Jewelry stones and technologies of their processing. Russian Chemistry Journal. 2010, vol. 54, no. 2, pp. 110—114. [In Russ].

13. Gvozdenko T. A., Gerasimova E. I. Possibilities of modern gemology. Priroda. 2018, no. 4 (1232), pp. 41—46. [In Russ].

14. Zablotskaya E. V., Ponomareva K. S. Defects of precious opals and methods of their elimination. Nauka i obrazovanie v oblasti tekhnicheskoy estetiki, dizayna i tekhnologii khudozhestvennoy obrabotki materialov. Materialy XI Mezhdunarodnoy nauchno-prakticheskoy konferentsii vuzov Rossii [Science and education in the field of technical aesthetics, design and technology of artistic processing of materials. Materials of the XI International Scientific and Practical Conference of Russian Universities], Saint-Petersburg, 2019, pp. 641—646. [In Russ].

15. Tilipalov V. N., Aleshkevich V. V., Peretyatko S. B., Akimov S. S. Patent RU 2187519, 20.08.2002. [In Russ].

16. Rossi M., Biondi R., Rizzi R., Corriero N., Sequino F., Vergara A. Mechanism of be-thermodiffusion in rutile inclusions of fancy sapphires. Crystal Growth & Design. 2022, vol. 22, no. 11, pp. 6493— 6503. DOI: 10.1021/acs.cgd.2c00700.

17. Vlasov A. V., Akhmetshin E. A. Patent RU 2738536, 14.12.2020. [In Russ].

18. Menchinskaya T. I. Biryuza [Turquoise], Moscow, Nedra, 1989, 192 p.

19. Klimkin I. A., Akhmetshin E. A. Radiation exposure as a method of modifying pale colored jewelry corundums. Uspekhi v khimii i khimicheskoy tekhnologii. 2023, vol. 37, no. 13 (275), pp. 78—80. [In Russ].

20. Nassau K. Gemstone enhancement. Histiry, Science and State of the Art. 2nd edition. Butterworth Heinemann Publishing Company, Oxford, Great Britain, 2012, 252 p.

21. Lushchik A., Seeman V., Shablonin E., Vasil’chenko E., Kuzovkov V. N., Kotomin E. A., Popov A. I. Detection of hidden oxygen interstitials in neutron-irradiated corundum crystals. Journal Optical Materials: X. 2022, vol. 14, pp. 1—10. DOI: 10.1016/j.omx.2022.100151.

22. Schmetzer K., Krzemnicki M. S., Hodgkinson A. Treated Ruby. Gems and Minerals. 2012, vol. 21, no. 3, pp. 14—17.

23. Emmett J. L., Douthit T. R. Heat treating the sapphires of rock creek, Montana. Gems & Gemology. 1993, vol. 29, no. 4, pp. 250—272.