Fridrichová J., Bačík P., Illášová Ľ., Štubňa J., Škoda R. & Milovská S., 2018: Forensic gemmological study of green-coloured beryl of variable origin. Acta Geologica Slovaca, 10, 2, 89–104.

Forensic gemmological study of green-coloured beryl of variable origin

Jana Fridrichová¹, Peter Bačík¹, Ľudmila Illášová², Ján Štubňa², Radek Škoda³ & Stanislava Milovská⁴

¹Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University in Bratislava, Ilkovičova 6, 842 15 Bratislava, Slovakia; jana.fridrichova@uniba.sk
²Gemmological Institute, Faculty of Natural Sciences, Constantine the Philosopher University in Nitra, Nábrežie mládeže 91, 949 74 Nitra, Slovakia
³Department of Geological Sciences, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic
⁴Earth Science Institute of the Slovak Academy of Science, Ďumbierska 1, 974 01 Banská Bystrica, Slovakia

Abstract

Fourteen gem-quality green-coloured beryl samples of different origin were investigated by standard gemmological methods and Raman, X-ray fluorescence and optical absorption spectroscopy. All investigated 14 samples were identified as beryl by Raman spectroscopy. Five main transition elements were detected (Cr, V, Fe, Cu, Ni). Six samples were significantly enriched in Cr . These samples also had the highest luminescence at about 685 and 680 nm corresponding to R1 and R2 bands which is good identification factor for emeralds. Two of these samples were also enriched in vanadium. In two other Cr-rich samples is also Ni and Cu present. These two samples contain also the highest amount of Fe, while the other samples contain lower amounts of Fe. In two of the Fe-bearing samples Cr was not detected. Varying amounts of water inclusions, both type I and II, were detected in each of the samples, except the two Ni- and Cu-bearing samples, which exhibit only H2O type I. While the samples with a high Cr content were assigned to emerald, the green Fe-rich samples (without Cr) can be named just as green beryl. It seems that a special Cr-V-Fe ratio is indicative for samples, which were found in Colombia. The other samples (except the Ni- and Cu-bearing samples) are likely from various schist-type emerald deposits. There are indications that the two Cu- and Ni-bearing samples with only water type I are Russian hydrothermal syntheses.

Key words: green-coloured beryl, chromophore, Raman spectroscopy, optical absorption spectroscopy, XRF, gemmology

Manuskript doručený: 2018-09-27

Manuskript revidovaný: 2018-11-22