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The article offers information the 6th Mediterranean Hybrid Gem and Jewellery Conference held in Thessaloniki, Greece from 12 to14 August 2022. The conference was organized by Branko Deljanin, George Spyromilios, and David Lazić and attended by representatives from nine countries. It includes information about the pre-conference tour and workshops on opal testing and valuation, colored diamond identification, and gemstone country of origin.

This paper presents the first evidence of lapis lazuli or lazurite that was detected unexpectedly using micro-Raman spectroscopy during research to identify an enigmatic purple hue on the thirteenth-century BC Greek Bronze Age wall paintings from Gla. The lapis lazuli material was found as part of a mixture including a red iron oxide and an as yet unidentified purple staining material. Existing purple mixtures of that period are also discussed. The identification of lapis lazuli at Gla may prove to be the earliest known use of this pigment in buon fresco, in both Eastern and Western painting traditions. Furthermore, this precedes the next known use of the material as a pigment by 1800 years. The existence of this blue pigment is also discussed within the context of the blue pigment palette of the Bronze Age Aegean and eastern Mediterranean Bronze Age (3300-100 BC), to show its use in relation to other blue materials and to demonstrate the technology and knowledge mastered by the artists who used this lazurite. [ABSTRACT FROM AUTHOR]

The Pirgadikia Terrane in northern Greece forms tectonic inliers within the Vardar suture zone bordering the Serbo-Macedonian Massif to the southwest. It comprises Cadomian basement rocks of volcanic-arc origin and very mature quartz-rich metasedimentary rocks. U–Pb laser ablation sector-field inductively-coupled plasma mass spectrometry analyses of detrital zircons from the latter reveal a marked input from a Cadomian–Pan-African source with minor contribution from Mesoproterozoic, Palaeoproterozoic and Archaean sources. The metasedimentary rocks are correlated with Ordovician overlap sequences at the northern margin of Gondwana on the basis of their maturity and zircon age spectra. The Pirgadikia Terrane can be best interpreted as a peri-Gondwana terrane of Avalonian origin, which was situated close to the Cadomian terranes in the Late Neoproterozoic–Early Palaeozoic, very much like the Istanbul Terrane. The second unit investigated is the Vertiskos Terrane, which constitutes the major part of the Serbo-Macedonian Massif in Greece. It comprises predominantly igneous rocks of Silurian age and minor metasedimentary rocks of unknown age and provenance. U–Pb analyses of detrital zircons from a garnetiferous mica schist of the Vertiskos Terrane indicate derivation from 550 to 1,150 Ma-old source rocks with a major Cadomian peak. This, combined with minor input of >1,950 Ma-old zircons and the absence of ages between ca. 1.2 and 1.7 Ga suggests a NW Africa source. The protolith age of the garnetiferous mica schist is presumably Early Ordovician. One sample of garnet-bearing biotite gneiss, interpreted as meta-igneous rock, comprises predominantly subhedral zircons of igneous origin with late Middle Ordovician to Silurian ages. We suggest that the rock association of the Vertiskos Terrane is part of an ancient active-margin succession of the Hun superterrane, comparable to successions of the Austro- and Intra-Alpine Terranes. The new data of this study provide evidence of occurrences of Avalonia- and Armorica-derived terranes in the Eastern Mediterranean and moreover help to clarify palaeogeographic reconstructions for the peri-Gondwana realm in the Early Palaeozoic. [ABSTRACT FROM AUTHOR]

Porphyroblastic garnet schists from northern Samos contain in their matrix the assemblage Ca-rich garnet + phengite + paragonite ± chloritoid equilibrated at ∼530 °C and ∼19 kbar during early Tertiary metamorphism. These high-pressure/low-temperature (HP-LT) metapelitic rocks also exhibit mineralogical and microstructural evidence of an older, higher temperature metamorphism. Large, centimetre-sized Fe-rich garnet showing growth zoning developed discontinuous, <0.5 mm thick, Ca-rich and Mn-poor overgrowths, compositionally matching small (<1 mm) high- P matrix garnet. Because the discontinuous garnet rims are in textural and chemical equilibrium with Alpine high- P minerals, the central parts of the garnet porphyroblasts were found to have formed prior to the Tertiary metamorphism. This is supported by electron microprobe U-Th-Pb dating of monazite inclusions yielding partly reset Variscan ages between 360 and 160 Ma. Monazite-xenotime and garnet-muscovite thermometry applied to inclusions in the pre-Alpine garnet yielded temperatures of 600–625 °C (at 3–8 kbar). Prismatic Al-rich pseudomorphs, possibly after kyanite/sillimanite, and inclusions in garnet composed of white K-Na mica + quartz ± albite ± K feldspar, interpreted as possible replacements of an intermediate K-Na feldspar, further support Variscan amphibolite facies conditions. The Samos metapelites thus experienced higher temperatures during the Variscan than during Alpine metamorphism. Diffusional relaxation was very limited between pre-Alpine garnet and Alpine garnet; both were filled with Alpine garnet along overgrowths and fractures. Fluid-mediated intergranular element transport, enhanced by deformation, appears crucial in transforming the Variscan garnet into a grossular richer composition during Alpine subduction-zone metamorphism. At such conditions, dissolution–reprecipitation appears to be a much more effective mechanism for modifying garnet compositions than diffusion. Amphibolite facies conditions are typical for Variscan basement relics exposed in central Cycladic and Dodecanese islands as well as in eastern Crete. The Samos metapelites studied comprise a north-eastern extension of these basement occurrences. [ABSTRACT FROM AUTHOR]