Light & Engineering 31 (4)

Volume 31
Date of publication 08/10/2023
Pages 94–100

Purchase PDF - ₽450

Gemstone Colour Determination L&E, Vol.31, No.4, 2023

Articles authors:

Valery E. Ivanov

Valery E. Ivanov, Ph. D. of Technical Sciences, Associate Professor. He graduated from Smolensk State Pedagogical Institute in 1974 with specialty in Physics. At present, he is Associate Professor of the Physics sub-department of Smolensk branch of NRU MPEI. His research interests: photometry and semiconductor photo-converters

Abstract:

The article describes the most important component of gemstones: their colour. The subject of the article is determination of the colour of diamonds with the most frequently encountered yellow tones of different saturation, fancy-colour diamonds as well as emeralds, rubies, and sapphires. For non-ambiguous determination of the colour of gemstones and elimination of human factor, the comparison method known in photometry, i.e., comparison of the colour of a given diamond with the colour of a reference sample is used. The article describes methods of determination of the colour of yellow-hue diamonds when assessing them visually, using reference colours: a set of diamonds. Information on colour groups of diamonds of different cuts used in Russia and the system of Gemological Institute of America (GIA) is provided.
Fancy colours of diamonds are very variable and, therefore, they have no references such as the ones for yellow-hue diamonds. For evaluation of fancy colours, the Munsell Book of Colour is used. It includes 1600 colour samples on 40 maps each having its own colour hue. The samples are arranged in rows and columns: samples of the same row have the same brightness; samples of the same column have the same saturation. As the samples for determination of fancy colours of diamonds as well as emeralds, rubies, and sapphires plastic plates of different colours are used. The colours of the examined gems are compared to them. The article describes the methods of assessment of fancy colours of diamonds adopted in Russia.
Nowadays, a software colour evaluation system is proposed by GIA to be used as an alternative to colour samples. Gemewizard software proposed by Izrael may identify 31 main colour tones. It reproduces each tone in six colour hues. Each hue is divided by six brightness levels. In general, this system allows us to determine 1116 colours of gemstones. The software approach had been already proposed previously but computer screens have different colour rendering, which is still the main hindrance for determination of gem colour by means of software.

References:

1. Standard,GOST R52913–2008: Polished diamonds Classification Technical requirements.
2. Shirokikh, T.V. Reflection of Radiation by Roundshaped Diamonds / Energetika, informatika, innovatsii: materialy X Natsionalnoy nauchno-tekhnicheskoy konferentsii s mezhdunarodnym uchastiem (Smolensk, Vol. 2., Smolensk: Universium, Smolensk branch of NIU MEI, 2020, Vol. 2, pp. 287–289.
3. Pagel-Theisen, V. Diamond Grading ABC / 12-th еdition, Antwerpen, 2000, 290 р.
4. Shirokikh, T.V. Analysis of Factors Affecting Diamond Colour / Energetika, informatika, innovatsii: materialy III Mezhdunarodnoy nauchno-tekhnicheskoy konferentsii (Smolensk, October 21–23, 2013). Vol. 1, Smolensk: Universium, Smolensk branch of NIU MEI, 2013, pp. 532–534.
5. Kiselyov, R.K. Colour of Faceted Stone, Perseption and Assessment // Gorny informatsionno-analiticheskiy bulleten (nauchno-tekhnicheskiy zhurnal), 2012, Vol. 6, p. 8.
6. Shirokikh, T.V., Ivanov, V.E. Diamond Colour Measurement // Light & Engineering, 2018, Vol. 26, # 3, pp. 109–115.
7. Drucker, R. Determination of Gem Quality and System of Their Colour Assessment // Gemstones market, 2007, Vol. 2, pp. 56–60.
8. Saiko, V. On GIA Gem Certification in Detail // Expo-yuvelir, 2022, Vol. 1 (124), pp. 3–5.
9. Meshkov, V.V., Matveev, A.B. Basics of Light and Engineering: A Study Guide for Universities: in 2 Parts. Part 2. Physiological Optics and Colorimetry / Moscow: ENERGOATOMIZDAT, 1989, 432 p.
10. Bocharov, A.M., Nyubin, V.V. Diamond Colorimetry / Smolensk: Smolensk Gemological Centre, 2008, 188 p.
11. Shirokikh, T.V., Nyubin, V.V. Diamond Colour Simulators // Svetotekhnika, 2001, # 6, pp. 11–14.
12. Chertov, A.N., Gorbunova, E.V., Kushkoeva, A.S., Alyokhin, A.A., Peretyagin, V.S., Pavlenko, N.A., Sychyova, E.A. Gemstone Colour Determination: from Visual Analysis to Instrumental Assessment // Izmeritelnaya tekhnika, 2019, Vol. 8, pp. 24–28.
13. Kiselyov, R.K. The Necessity of Updating of the Faceted Stone Colour Determination System // Nauchny vestnik Moskovskogo gosudarstvennogo gornogo universiteta, 2012, Vol. 9, pp. 30–37; https://www.elibrary.ru/contents.asp?id=33747841.
14. Lagutenkov, A.A. Introduction of GIA 4C for Coloured Gemstones Gemstone Assessment // Expo-yuvelir, 2017, Vol. 2 (105), pp. 9–12.
15. STO-DSC‑0005–05–2016 Natural Emeralds. Technical Requirements.
16. STO-DSC‑0004–05–2016 Natural Corundum: Rubies and Sapphires. Technical Requirements.

Keywords

DOI: https://doi.org/10.33383/2022-073

Article in RUS:
Svetotekhnika # 2, 2023, pp. 54–59

Buy