Amber is a fossil resin that has had a social value since the Upper Paleolithic. This is due to its unique natural characteristics, which have made it widely used and socially valued throughout prehistory, especially as a decorative and as a symbolic element. The Baltic coast and Sicily are the main natural sources of amber exploited in prehistory. Since the beginning of modern research, the presence of amber outside these regions has been used as an indicator of the existence of long-distance exchange networks (de Navarro, 1925), and consequently amber has been considered an exotic and prestigious material. On this basis, a solid tradition of research has been established to identify the origin of amber objects (Beck, 1995; Beck et al., 1965, 1964; Beck and Hartnett, 1993), which has led to the identification of spatiotemporal patterns of their consumption. The characterization of prehistoric amber ornaments has been extensively addressed in recent years (Murillo-Barroso et al., 2018; Murillo-Barroso and Martinón-Torres, 2012; Odriozola et al., 2019b), given the strong tradition of studies on this raw material of high symbolic value.

Fourier transform infrared spectroscopy (FTIR) analyses have confirmed long-distance exchange as the main form of access to amber, allowing the identification of two large-scale trends in exchange flows, starting from Sicily in the 4th-3rd millennia BC and swinging to the Baltic Sea from the 2nd millennium BC (Odriozola et al., 2019b). Despite this exogenous trend, in the last decades the focus has also been put on the geological deposits of Iberian amber, with the documentation of different local sources of amber on the Cantabrian coast (Álvarez Fernández et al., 2005; Murillo-Barroso et al., 2018). On the other hand, numerous local amber outcrops remain to be characterized, such as those between the Tagus and Mondego estuaries in Portugal (Peñalver et al., 2018). Despite the acknowledged long-distance exchange of Baltic and Sicilian amber, and the lack of a comprehensive spectral record of Portuguese amber, scientists have recently suggested that Sicilian and Portuguese amber have similar spectral characteristics, compromising origin identification. Consuming local instead of foreign amber would therefore completely change the image of a united Europe.