Tom Stephan, M.Sc.

Born in Idar-Oberstein, Germany.

Study of geoscience at the Johannes Gutenberg University in Mainz, Germany.

Master thesis (2016) with gemmological background. Ph.D. thesis (since 2016) with gemmological background in work.

Since 2014 scientific assistant for research and education at the German Gemmological Association.

Author of various articles in international journals.

The role of V3+ in gemstones coloured mainly by Cr3+, shown by spectral fitting at the example of emerald and ruby


Emerald and ruby are coloured mainly by trivalent chromium. Both, however, can also incorporate trivalent vanadium. Their absorption spectra are dominated by the absorption bands of chromium, which are overlapping the vanadium bands almost completely. For the research presented, spectral fitting is used to subdivide the absorption spectra of emeralds and rubies of various origins into their single components. By subtracting the fitted Cr3+- or V3+- absorption bands from the whole spectrum, the influence of each of them on the colour impression can be shown.

Impressions from the first EGS 2007 in Idar-Oberstein

Register for the European Gemmological Symposium
on May 24 – 26, 2019 in Idar-Oberstein.

During the two days’ conference, you will enjoy numerous internationally recognized and distinguished speakers, as well as a broad spectrum of subjects including diamonds, coloured stone, pearls and jewellery.

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