Fridrichová J., Bačík P., Škoda R. & Antal P., 2015: Use of spectroscopic methods for determination of diamond origin and treatment. Acta Geologica Slovaca, 7, 1, 11–18.

Use of spectroscopic methods for determination of diamond origin and treatment

Použitie spektroskopických metód na určenie pôvodu a úprav diamantov

Jana Fridrichová¹, Peter Bačík¹, Radek Škoda² & Peter Antal³

¹Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia; fridrichova@fns.uniba.sk
²Department of Geological Sciences, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
³Department of Inorganic Chemistry, Faculty of Natural Sciences, Comenius University in Bratislava, Mlynská dolina, Ilkovičova 6, 842 15 Bratislava, Slovakia

Abstract

Eleven brilliant cut yellow and brown diamonds were studied by non-invasive spectroscopic methods and devices. At first, identification was proven by Raman spectroscopy according to presence of Diamond Raman band at ca. 1330 cm^–1 in each sample. UV/Vis/NIR spectroscopy was used as a potential tool to determine the diamond type. All studied stones were classified based on the presence of N3 – zero phonon line at 415 nm attributed to diamond Ia type which is the most abundant type in natural diamonds. This type consists of N atoms surrounding a vacancy. It suggests that diamond structure contains domains of type IaB diamond. Consequently, on the basis of type was excluded synthetic origin of the samples because this type was already not prepared artificially. Using Raman and UV/Vis/NIR spectroscopy, defects in diamond structure were detected and HPHT treatment was also determined. The main observable defects include N-V0 at 575 nm, N-V^– at 638 nm, N3 at 415 nm, and H3 at 503 nm. The presence of these defects can be main indicator in HPHT treated stones. Only two studied samples significantly displayed all of these defects attributed to HPHT treatment, but other samples also showed tracks of treatment. This gemmological investigation results in estimating the original most likely brown diamond colour and probably intermediate temperature during HPHT processing.

Key words: diamonds, identification, „Type” classification, origin, HPHT treatment, UV/Vis/NIR spectroscopy, Raman spectroscopy

Manuscript received: 2014-09-18

Revised version accepted: 2015-01-29