**1. Introduction**

Volcanic obsidian was widely used in ancient times for stone tools, with its highly glassy nature making it sharper than other lithics for cutting purposes. In Europe and the Mediterranean, there are just several island sources in Italy and Greece, and a few in the inland Carpathian region, all having been used by the beginning of the Neolithic period, ca. 6000 BCE. Maritime transport was necessary for access to the island sources, while other materials would have been moved in opposite directions. Obsidian was likely a small part of this exchange system. The location and geological studies for each of the sources goes back to the early 20th century, while the ability to chemically identify specific sources began in the 1960s. The development of non-destructive and especially portable X-ray fluorescence spectrometers has revolutionized the number of artifacts tested since 2010, providing new interpretations of obsidian selection and use, which changed over time.
