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

  • Thennakoon Gamage Ramesh Mr.
  • Ramawickrama G. Chamal Jaliya
  • IIlangasinghe Kalukumara M. S. C. Kumara Illangasinghe
  • Kuruppu Arachchige D. D. Nimanthika Kuruppu
Keywords: ED-XRF and FTIR analysis, Localization effect, Milky Geuda, Heat treatment of Geuda, Geuda identification


Over 75% of the gem-bearing gravels in Sri Lanka belong to the corundum species of gemstones. Geuda is a low-quality form of corundum, and it is abundant in most gem-enriched regions in Sri Lanka. It can be heat treated to transfer into worthy blue sapphires where the value alters with the degree of colour. However, the degree of colour enhancement is uneven in Geuda stones even if the heat treatment is conducted under the same conditions. Thus, this study focuses on evaluating the effect of localization on the colour enhancement of the milky Geuda variety. Fifty Geuda samples were collected from five gem-bearing localities in Sri Lanka; Ratnapura, Ridiyagama, Okkampitiya, Bakamuna, and Katharagama. These samples were washed and sonicated with dil. HNO3 acid and facetted to have parallel smooth surfaces. Then all samples were observed and analyzed under a microscope, ED-XRF, FTIR, and UV-Vis spectroscopies and heated up to 1800 °C temperature for 60 minutes of the soaking period under reducing conditions. Then the analyses except XRF were repeated (before and after the heat treatment). Microscopic observations support visually identifying the degree of colour enhancement and inclusions changes. UV-Vis spectrums identified the cause of blue colour enhancement as the intervalence charge transfer (IVCT) developed by Fe2+ and Ti4+ ions, and the change in the degree of colour enhancement was also verified as an alteration in the degree of IVCT by the available ions. FTIR spectrum characterized the bond vibrational changes with the heat treatment, and FTIR was clarified as the best method to identify heat-treated blue sapphires since a characteristic peak was generated at 3310 cm-1 after treatment. Apart from Ti and Fe, V was also determined to affect blue colour enhancement by ED-XRF analysis. The optimum blue colour was enhanced in the ratios of 1: 3: 323 for Ti: Fe: Al. there were significant changes in the location and ternary diagrams are accompanied to record the highest Ti content in Ridiyagama and the highest Fe content in Bakamuna and Katharagama. Furthermore, corresponding unique elemental ratios for these localities were encountered.


Beran, A., 1991. Trace hydrogen in Verneuil-grown corundum and its colour varieties: An IR spectroscopic study. European Journal of Mineralogy 3 (6), 971-975.

Catier, L.E., 2009. Ruby and sapphire from Marosely, Madagascar. Journal of Gemmology 31 (5-8), 171-179.

Cooray, P.G., 1994. The Precambrian of Sri Lanka: a historical review. Precambrian Research 66 (1-4), 3-18.

Dahanayake, A.P., Liyanage, K., Ranasinghe, A.N., 1980. Genesis of sedimentary gem deposits in Sri Lanka. Sedimentary Geology 25 (1-2), 105-115.

De Maesschalck, I.S., Oen, A.A., 1989. Fluid and mineral inclusions in corundum from gem gravels in Sri Lanka. Mineralogical Magazine 53 (373), 539-545.

Dissanayake, H.J., Chandrajith, C.B., Tobschall, H., 2000. The geology, mineralogy and rare element geochemistry of the gem deposits of Sri Lanka. Bulletin of The Geological Society of Finland 72 (1/2), 5-20.

Dissanayake, M.S., Rupasinghe, C.B., 1995. Classification of gem deposits of Sri Lanka. Geologie en Mijnbouw 74, 69-79.

Emmett, R.E., Scarratt, J.L., McClure, K., Moses, S.F., Douthit, T., Hughes, R., Kane, R., 2003. Beryllium diffusion of ruby and sapphire. Gems Gemology 39 (2), 84-135.

Ferguson, P.E., Fielding, J., 1971. The origin of the colours of yellow, green and blue sapphires. Chemical Physics Letters 10 (3), 262-265.

Fritsch, G.R., Rossman, E., 1987. An update on color in gems. Part I. Introduction and colors caused by dispersed metal ions,” Gems and Gemology 23, 126-139.

Geiger, E., Beran, C.A., Libowitzky, A., 2004. An introduction to spectroscopic methods in the mineral sciences and geochemistry. Book Chapter in European Mıneralogıcal Unıon Notes in Mıneralogy Spectroscopic Methods in Mineralogy, Mineralogical Society of Great Britain and Ireland.

Ileperuma, O., 1993. Chemistry of Geuda Heat Treatment. In National Symposium on Geuda Heat Treatment, 1993, pp. 99-104.

Jaliya, R.G.C., Dharnaratne, P.G.R., Wijesekara, K.B., 2020. Characterization of heat treated geuda gemstones for different furnace conditions using FTIR, XRD and UV–Visible spectroscopy methods. Solid Earth Sciences 5 (4), 282-289.

Jaliya, R.G.C., Dharmaratna, P.G.R., Wijesekara, K.B., 2019. Colour Development of Geuda Stones after the Gas-Fired and Electrically Operated Furnace Heat Treatments. Journal of Technology and Value Addition 1 (1), 46-51.

Katz, M.B., 1986. Review of the geology of the gemstones of Sri Lanka. The Australian. Gemmologist 20, 52-61.

Moon, M.R., Philips, A.R., 1994. Defect clustering and color in Fe,Ti: α-Al2O3. Journal of the American Ceramic Society 77 (2), 356-367.

Nassau, K., 1997. Color for science, art and technology. Elsevier, Vol. 1.

Nassau, K., 1983. The physics and chemistry of color: The fifteen causes of color. Wiley, New York.

Peiris, B.P.S., 1993. Colour Enhancement of Diesel Geuda. In National Symposium on Geuda Heat Treatment, 1993, pp. 113-121.

Pemadasa, T.G., 1993. Heat Treatment of Different Types of Geuda. In National Symposium on Geuda Heat Treatment, 1993, pp. 123-127.

Perera, H.P.N.J., Gunasekera, I., 1993. Identification of Treatable Geuda by Spectral Investigations. In National Symposium on Geuda Heat Treatment, 1993, pp. 89-97.

Rupasinghe, D.P.J., Dissanayake, M.S., Mendis, C.B., 1994. Use of indicator minerals in gem exploration: study of a granulitic terrain in Sri Lanka. Journal of Southeast Asian Earth Sciences 9 (3), 249-254.

Rupasinghe, O.A., Rupasinghe, M.S., Dissanayake, R.A.P. Ileperuma, C.B., 1993. Definition and Classification of Geuda. In National Symposium on Geuda Heat Treatment, 1993, pp. 01-13.

Schwarz, D., Pardieu, V., Saul, J.M., Schmetzer, K., Laus, B., M., Giuliani, G., Klemm, L., Malsy, A., Erel, E., Hauzenberger, C., Toit, G.D., Fallick, A.E., Ohnenstetter, D., 2008. Rubies and Sapphires from Winza, Central Tanzania. Gems Gemology 44 (4), 322-347.

Smith, S., Kammerling, C.P., Keller, R.C., Peretti A.S., Scarratt, A., Khoa, K.V., Repetto, N.D., 1995. Sapphires from southern Vietnam,” Gems and Gemology 31 (3), pp. 168-186.

Smith, B., Fagan, C.P., Clark, A.J., 2016. Ruby and Pink Sapphire from Aappaluttoq, Greenland. Journal of Gemmology 35 (4), 294-305.

Smith, C.P., 1995. A contribution to understanding the infrared spectra of rubies from Mong Hsu, Myanma. Journal of Gemology 24 (5), 321-335.

Soysa, W.S., Fernando, E.S.K., 1992. A field classification of low value corundum in Sri Lanka. Journal of the National Science Foundation of Sri Lanka 20 (1), 51-57.

Zwaan, P.C., 1982. Sri-Lanka: the gem island. Gems and Gemology 18 (2), 62-71.