The combined use of Raman and micro‐X‐ray diffraction analysis in the study of archaeological glass beads

Abstract

This study proposes a new nondestructive methodology that combines micro-Raman spectroscopy and micro-X-ray diffraction (μ-XRD), complemented by variable pressure scanning electron microscopy coupled with energy dispersive X-ray spectrometry, to determine the composition of glass artifacts and the manufacturing techniques employed in their production. The use of micro-Raman spectroscopy revealed that most samples belong to the alkaline glass family. Chemical analysis also allowed the identification of the main colorants used in the manufacture of the glass beads in this study. Dark blue and turquoise glass were colored using cobalt ions and copper ions, respectively.Amber or light brown hues were produced using the iron-sulfur amber chromophore. Iron ions were also used to produce green, yellow, cream-colored gray, and black hues. White glass was produced using calcium antimonate phases. These compounds, identified by micro-Raman spectroscopy and μ-XRD, were also used as opacifying agents. This study highlights the importance of using micro-Raman spectroscopy in the study of ancient glass artifacts. In fact, micro-Raman spectroscopy not only allows the determination of the glass family of heavily degraded samples but was also found to be the only technique capable of identifying evidences of the rearrangement of the silicate network following selective leaching. The combined use of micro-Raman spectroscopy and μ-XRD permitted the identification of the opacifying agents and heat treatment used in the manufacture of the opaque glass beads in this study.

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

“…By applying this criterion, the pieces can be classified into two groups: those dominated by the δ (Si-O) deformation modes (pieces number 3, 5, 10, 12, and 13) and those with predominant ν (Si-O) stretching bands (the rest). The dispersions for the peak wavenumber of the νQ n stretching bands are about 18,29,22,26, and 31 cm −1 for νQ 0 , νQ 1 , νQ 2 , νQ 3 , and νQ 4 , respectively. These low dispersions suggest that the thermal treatments and chemical compositions of the analyzed pieces are similar so that they can be associated with a shared technological pattern.…”

“…[23][24][25] Moreover, Phoenician-Punic glass beads found in the Iron Age necropolis of Vinha das Caliças (Beja, Portugal) were analyzed by RS providing information about their manufacture, using firing temperatures about 1000 C, and detecting some opacifiers and pigments employed in their production. [26] Also the RS analysis of glass beads of the Reliquary bust of Saint Lambert (Liège Cathedral, Belgium) allowed separated identification of the original beads, contemporary with the bust, from beads that were added to the bust latter. [27] Regarding the Iberian Peninsula, RS has only been employed to study the pre-Roman glass beads found in the archaeological sites of Tutugi (Galera, Granada, Spain) [9] and Cerro de los Vientos (Baeza, Jaen, Spain).…”

Recent advances in linear and nonlinear Raman spectroscopy. Part XIV

“…14.1 | Glasses, ivory, resins, porcelain, pottery, bronzes, panes, fossils, seashells, gemstones, and pearls Costa et al [120] described the combined use of Raman and micro-X-ray diffraction analysis in the study of archaeological glass beads. Their method allowed the identification of the opacifying agents and heat treatment used in the manufacture of the opaque glass.…”

Applications of Raman spectroscopy in art and archaeology

“…The composition of archaeological glass beads and the manufacturing techniques employed in their production was ascertained by Costa et al [20] based on a new nondestructive methodology that combines micro-Raman spectroscopy and micro-X-ray diffraction (μ-XRD), complemented by variable pressure scanning electron microscopy coupled with energy dispersive X-ray spectrometry. The work revealed that most samples belong to the alkaline glass family and identified the main colorants used in the manufacture of the studied glass beads.…”