Investigating glass beads and the funerary rituals of ancient Vaccaei culture (S. IV‐I BC) by Raman spectroscopy

Abstract

Glass pieces were highly appreciated goods in the Protohistory of the Iberian Peninsula. The specialized production of these glass pieces seems noncompatible with local workshops, and therefore, they are proof of commercial relationships with other cultures with the technical capability to produce such pieces. However, detailed studies of glass beads of archaeological relevance are scarce, as these samples usually appeared without a clear historical context. Nevertheless, the archaeological site of Pintia (Padilla de Duero, Valladolid, Spain) is a relevant exception to this situation. About 600 pieces have been recovered by 2018, with a significant percentage found in closed tombs. In this work, a set of 15 representative pieces from the Vaccaei culture (IV‐I centuries BC) have been studied by Raman spectroscopy and ESEM/EDX. The combination of both techniques provided valuable information about the fabrication of these samples, identifying diverse features that could be related to different workshops or origins. In particular, the characteristics of a sophisticated bifacial pendant were found to be compatible with their provenance from Carthage. Also, some of the pigments employed on these samples were identified by Raman spectroscopy, finding lead oxides, calcium antimoniate, hematite, and Naples yellow. The diverse trousseaus and viatic offerings found in the Vaccaei tombs show the relevance and complexity of the funerary cremation rituals in their culture. The study by Raman spectroscopy of well‐preserved and thermally altered glass beads found in the same tomb allowed estimating the maximum temperature reached during the cremation in about 600°C, which confirmed previous estimations derived from the state of conservation of the bone remains.

Raman Spectroscopy Study of Ancient Vaccaei (s. IV-I BC) Glass Beads found at the Necropolis of “Las Ruedas” (Padilla de Duero, Valladolid, Spain)

“…The results of Raman spectroscopy did not show the presence of complex pigments for most of the samples, being necessary to rely on the elemental characterization provided by ESEM/EDX, which related the blue hues to the presence of MnO and Fe 2+ , green hues to the presence of Fe +2 and Cu +2 . On the contrary, further analysis by Raman spectroscopy evidences the presence of a complex lead antimoniate-based pigment (e.g., Naples Yellow) on the orange glass bead, which suggest a potential provenance from an advanced workshop (2).…”

Known Glass Compositions in Iron Age Europe—Current Synthesis and Emerging Questions

“…The SEM-EDS results for the 4th-1st c. BCE Pintia beads also show higher Al2O3 values, seemingly providing an argument in favour of a high-Al glass being in circulation in the western Mediterranean in the second half of the [41,94,95] and Portugal [40], compared to a larger dataset for LMG small finds from Europe. Data for LMG were obtained from various publications [31,33,37,[39][40][41][42]57,84,[90][91][92][93][94][95][96][97].…”

“…It is definitely interesting to note that only the natron-fluxed glass from the western Mediterranean exhibits unusually high alumina contents [94,95]. It still remains to be seen if this could signify the existence of a Western glass supply chain, because data for Iron Age vitreous materials from the Iberian Peninsula and the islands are overall limited [40,41,[94][95][96][97][98][99][100][101][102][103][104][105][106][107][108][109][110][111][112]. Beads with a high Al 2 O 3 content (3.42-14.41 wt.…”

“…Beads with a high Al 2 O 3 content (3.42-14.41 wt. %), compared to the "typical Hellenistic" composition of other beads from the Iberian Peninsula found in Portugal [40] and on Menorca [41], come from Pintia (Spain) [95] and So na Caçana (Spain) [94]. Links with Asian high-Al plant ash glasses can easily be ruled out since a completely different flux was used to make those beads [109].…”

Applications of Raman spectroscopy in art and archaeology

“…The work conducted by Pinto et al [ 24 ] on some archaeological glass pieces from the Pintia archaeological site (Padilla de Duero, Valladolid, Spain) gave information on the local production processes of the Vaccaei culture. Glass beds were highly appreciated goods in the Protohistory of the Iberian Peninsula, but the known specialized production of those glass pieces seemed to be noncompatible, in opinion of the archaeologists, with beds found in Pintia, suggesting local workshops with own production processes.…”