The V^th century AD jewellery from Cluj-Napoca (Romania): a nondestructive investigation

The 2007 archaeological excavations carried out at the Polus Centre 5 km west of Cluj- Napoca (Romania), exhumed among others a princely tomb containing gold jewellery. It belongs to the Gepids, an East Germanic tribe which settled down in the nowadays Transylvania, in the second half of the V^th century AD. Nine gold pendants inlaid with a total of 45 slices of red gemstone were subject of a non-invasive (nor sampling neither dismounting of the gems from the jewels) and non-destructive (no damage to the gem) study. Previously, the gemstones were macroscopically assigned to the ruby variety of corundum.
   Each pendant has a total length around 3.85 cm and consists of two parts: a leaf-shaped lower one, with four tablet-cut gemstones and an upper part, half moon shaped, with one gemstone. The stones are mounted in the cabochon technique and backed by a paillon – a reflecting layer of thin golden foil, stamped with a very regular and small cross-hatched pattern. Tiny gold balls decorate the pendants.
   The observation with a stereomicroscope under normal light shows that gemstones consist of a highly transparent, dark red material. Almost each piece has a number of tiny inclusions, such as crystallographically oriented rutile needles intersecting at 70º, rutile „dust”, negative crystals, and probably apatite. Black, sometimes hexagonal-shaped, platy crystals are most likely ilmenite and occur frequently. The VIS spectra revealed absorption bands in the violet and the blue/green transition zone, which can be assigned to Fe. The refraction index of some gemstones, measured with a Standard refractometer, is 1.78. The gemstones are isotropic.
   The X-Ray diffraction and X-Ray fluorescence analyses on the pendant inner side showed only Au lines. No traces of other elements such as Ag, Te, Cu, Hg, Sb, Pt, Sn, which might allow tracing the origin of the gold, were seen. The pendant face containing gemstones additionally produced Fe lines. The Raman spectroscopy analysis in respect to the gemstones shows the typical spectrum of almandine, with the 350, 500, 550 and 915 cm^-1 bands.
   Based on optical characteristics, inclusion types, as well as the XRD, XRF and Raman spectroscopy data, the gemstones from the Vth century AD Gepidic pendant are most likely garnet group minerals, i.e. almandine.
   Acknowledgements: The study was financially supported by ID-2241 project funds (Romanian Ministry of Education).