Vol. 337 No. 10 (2026)
DOI https://doi.org/10.18799/24131830/2026/10/5319
Black and gray nephrite of the Kavokta deposit, Middle-Vitim mountain country: properties and mineral composition
Relevance. The Kavokta deposit contains gray and black dolomite type nephrite, which is in high demand. Despite the fact that black nephrite has been found in several deposits, the reasons for its color are not well understood. Aim. To identify the localization and mineral composition of gray and black nephrite, and to determine the reasons for this color. Methods. The mineral composition of nephrite was studied using a scanning electron microscope with energy-dispersive microanalysis, X-ray phase analysis, and the isotopic composition of graphite carbon in nephrite and carbonates in the surrounding strata was determined. Results and conclusion. The gray to black color of most samples from the southeastern part of the Kavokta deposit (lodes 17 and 28 of the nephrite-bearing zone 4 of the Medvezhy section and lode 6-1 of the nephrite-bearing zone 6 of the Levoberezhny section) is due to the presence of graphite. Sigenetic graphite is formed both by the organic matter buried in dolomites and by the decomposition of carbon dioxide that appears during decarbonization under the effect of deep-seated hydrogen. The color of nephrite also depends on the iron content, changing from white to light green as the iron content increases. The gray color of tremolite-diopside nephrite is due to the development of chlorite aggregates that replace diopside and/or tremolite. The gray-green to black color of the nephrite in the northwestern part of the Kavokta deposit (lode 1 of the nephrite-bearing zone 1 of the Prozrachny section) is due to the high iron content in the tremolite to actinolite at the contact with the after amphibolite epidote-tremolite skarn. The identified patterns of black nephrite localization can be used in geological exploration.
For citation: Kislov E.V., Kotova I.Yu., Posokhov V.F., Trofimov A.V., Khromova E.A. Black and gray nephrite from the Kavokta deposit, Middle-Vitim mountain country: properties and mineral composition. Bulletin of the Tomsk Polytechnic University. Geo Assets Engineering, 2026, vol. 337, no. 10, pp. 226–241. http://doi.org/10.18799/24131830/2026/10/5319
Keywords:
nephrite, black color, Kavokta deposit, tremolite, actinolite, diopside, graphite, chlorite
References:
1. Kievlenko E.Y. Geology of gems. Littleton, CO, USA, Ocean Publ. Ltd., 2003. 432 p.
2. Harlow G.E., Sorensen S.S. Jade (nephrite and jadeitite) and serpentinite: metasomatic connections. Int. Geol. Rev., 2005, vol. 47, pp. 113–146.
3. The State Balance of Mineral Reserves of the Russian Federation as of January 1, 2024. Iss. 79. Colored Stones. Compiled by O.V. Voskova. Ed. by G.P. Kovtonyuk. Moscow, Russia, Federal State Budgetary Institution “Russian Federal Geological Foundation”, 2024. 284 p. (In Russ.)
4. Casadio F., Douglas J.G., Faber K.T. Noninvasive methods for the investigation of ancient Chinese jades: an integrated analytical approach. Analytical and Bioanalytical Chemistry, 2007, vol. 387, pp. 791–801. DOI: 10.1007/s00216-006-0684-y
5. Douglas J.G. The study of Chinese archaic jades using non-destructive X-ray fluorescence spectroscopy. Acta Geologica Taiwanica, 1996, vol. 32, pp. 43–54.
6. Wilkins C.J., Tennant W.C., Williamson B.E., Mccammon C.A. Spectroscopic and related evidence on the coloring and constitution of New Zealand jade. American Mineralogist, 2003, vol. 88, pp. 1336–1344. DOI: 10.2138/am-2003-8-917
7. Liu Y., Deng J., Shi G., Yui T.-F., Zhang G., Maituohuti A., Yang L., Sun X. Geochemistry and petrology of nephrite from Alamas, Xinjiang, NW China. Journal of Asian Earth Sciences, 2011, vol. 42, pp. 440–451. DOI: https://doi.org/10.1016/j.jseaes.2011.05.012
8. Liu Y., Deng J., Shi G., Sun X., Yang L. Geochemistry and petrogenesis of placer nephrite from Hetian, Xinjiang, Northwest China. Ore Geology Reviews, 2011, vol. 41, pp. 122–132. DOI: https://doi.org/10.1016/j. oregeorev.2011.07.004
9. Zheng J., Chen L., Zhang C., Liu Y., Tian R., Wu J., Wu Y., Zhang S. Constraints on crystallinity of graphite inclusions in nephrite jade from Xinjiang, Northwest China: implications for nephrite jade formation temperatures. Minerals, 2023, vol. 13, 1403. DOI: https://doi.org/10.3390/min13111403
10. Fang T., Chang Y., Yang M. Nephrite from Xinjiang Qiemo Margou deposit: gemological and geochemical insights. Minerals, 2024, vol. 14, 458. DOI: https://doi.org/10.3390/min14050458
11. Zhang Y.-D., Yang R.-D., Gao J.-B., Chen J., Liu Y.-N., Zhou Z.-R. Geochemical characteristics of nephrite from Luodian County, Guizhou Province, China. Acta Minerlogica Sinica, 2015, vol. 35, pp. 56–64. (In Chinese) DOI: https://doi:10.16461/j.cnki.1000-4734.2015.01.009
12. Zhong Q., Liao Z., Qi L., Zhou Zh. Black nephrite jade from Guangxi, Southern China. Gems and Gemology, 2019, vol. 55, pp. 198–215. DOI: https://doi.org/10.5741/GEMS.55.2.198
13. Gong N., Wang C., Xu S. Color origin of greyish-purple tremolite jade from Sanchahe in Qinghai Province, NW China. Minerals, 2023, vol. 13, 1049. DOI: https://doi.org/10.3390/min13081049
14. Flint D.J., Dubowski E.A. Cowell jade province: detailed geological mapping and diamond drilling of jade and ornamental marble outcrops, 1982–1987. Department of mines and energy of South Australia, 1989, Rept. Bk. No. 89/51. Dme No. 85/88, vol. 1. 323 p.
15. Adamo I., Bocchio R. Nephrite jade from Val Malenco, Italy: review and update. Gems and Gemology, 2013, vol. 49, pp. 98–106. DOI: https://doi.org/10.5741/GEMS.49.2.98
16. Shi G., Jia R., Santosh M., Liang H., He Y. First report of a nephrite deposit from Somaliland, Africa: characterization and geological and archaeological implications. Geological Society of America Bulletin, 2024, vol. 136, pp. 661–672. DOI: https://doi.org/10.1130/B36826.1
17. Suturin A.N., Zamaletdinov R.S., Sekerina N.V. Deposits of nephrite. Irkutsk, Russia, ISU Publ. House, 2015. 377 p. (In Russ.)
18. Nemeth K., Sági T., Józsa S. Why the pounamu? Low- to medium grade metabasites and metaultrabasites of New Zealand from a geoheritage perspective. Metamorphic Rocks as Key to Understand Geodynamic Processes, 2024, pp. 1–18. DOI: https://doi:10.5772/intechopen.1004738
19. Jutras J.-P., Williams C., Williams B., Ream L. Nephrite jade from the Sky Zone, Wyoming, USA: characteristics and primary hydrothermal origin. Journal of Gemmology, 2024, vol. 39, pp. 36–53. DOI: https://doi.org/10.15506/JoG.2024.39.1.36
20. Mustoe G.E. Pleistocene glacial transport of nephrite jade from British Columbia, Canada, to Coastal Washington State, USA. Geosciences, 2024, vol. 14, 242. DOI: https://doi.org/10.3390/geosciences14090242
21. Gomboev D.M., Androsov V.P., Kislov E.V. Kavokta deposit of light-colored nephrite: occurrence and characteristics of the composition. Prospect. Prot. Miner. Resour., 2017, vol. 9, pp. 44–50. (In Russ.)
22. Kislov E.V. Mineral composition and genesis of dolomite type nephrite, Kavokta deposit, Middle Vitim mountain country: vein 1 of site Prozrachny. Geosfernye issledovaniya, 2025, no. 1, pp. 79–94. (In Russ.). DOI: 10.17223/25421379/34/6
23. Kislov E.V. Kavokta deposit, Middle Vitim Mountain Country, Russia: composition and genesis of dolomite type nephrite. Geosciences, 2024, vol. 14, 303. DOI: doi.org/10.3390/geosciences14110303
24. Kozlov S.A., Novchenko S.A., Bogach G.I. State geologic map of the Russian Federation. Scale 1:1000000 (third generation). Series Aldan-Zabaikalskaya. Sheet N-50 – Sretensk. Explanatory note. St Petersburg, VSEGEI Publ., 2010. 377 p. (In Russ.)
25. Nikitin A.V., Patrakhin E.G. Paleozoic magmatism of the Western Transbaikalia (geology, material composition, age and geodynamics of formation). Vestnik of Voronezh University. Geology, 2002, no. 1, pp. 150–163. (In Russ.)
26. Minina O.R., Doronina N.A., Kurilenko A.V., Neberikutina L.N., Tashlykov V.S. Biostratigraphy of the Devonian-Lower Carboniferous deposits of the Bambuysko-Olingda Subzone (South Muya Ridge, Western Transbaikalia). Stratigraphy and geological correlation, 2023, vol. 30, pp. S1–S22. DOI: 10.1134/S0869593823010057
27. Filippova A.A., Mekhonoshin A.S., Bychinsky V.A., Chudnenko K.V. Physico-chemical features of fluides, which formed apohyperbasite, and apocarbonate jades. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2021, vol. 332, no. 3, pp. 168–178. (In Russ.) DOI: 10.18799/24131830/2021/03/3112
28. Hoefs J. Stable isotope geochemistry. Berlin, Heidelberg, Germany, Springer-Verlag, 2009. pp. 53–107.
29. Schidlowski M. Carbon isotopes as biogeochemical recorders of life over 3.8 Ga of Earth history: evolution of a concept. Precambrian Res., 2001, vol. 106, pp. 117–134.
30. Ryabov V.V., Ponomarchuk V.A. Petrology of the Kureika graphite deposit in the roof of the First-rapid trap intrusion (Siberian Platform). Russian Geology and Geophysics, 2023, vol. 64, pp. 795–809. DOI: 10.2113/rgg20234492
31. Sharp Z. Principles of stable isotope geochemistry. Upper Saddle River, New Jersey, Pearson Prentice Hall, 2007. 344 p.
32. Knauth L.P., Kennedy M.J. The late Precambrian greening of the Earth. Nature, 2009, vol. 460, pp. 728–732.
33. Weis P.L., Friedman I., Gleason J.P. The origin of epigenetic graphite: evidence from isotopes. Geochim. Cosmochim. Acta, 1981, vol. 45, pp. 2325–2332.
