Micro‐Raman spectroscopy and complementary techniques (hXRF, VP‐SEM‐EDS, μ‐FTIR and Py‐GC/MS) applied to the study of beads from the Kongo Kingdom (Democratic Republic of the Congo)

Abstract

In the framework of the inter‐disciplinary KongoKing project, a set of beads from archaeological excavations in the Democratic Republic of the Congo was analysed by means of a minimally invasive, multi‐analytical approach based on micro‐Raman spectroscopy. The full characterization of the materials, including glassy network, opacifiers and colorizers, was achieved thanks to the combination of data from handheld X‐ray fluorescence, variable pressure scanning electron microscopy coupled with energy‐dispersive X‐ray spectrometry, micro‐Fourier transform infrared spectroscopy and pyrolysis coupled to gas chromatography and mass spectrometry. The obtained chemical information was used to fill the existing gap in the chemical study of beads from Western Central Africa. The cobalt‐rich blue beads were found to be of Central European origin, while the copper‐rich turquoise beads were manufactured using distinct copper sources. Cadmium yellow and cadmium red are the colourants responsible for the bright colours of bead types 10 and 12, respectively. The type 12 beads were found to be composed of glass covered with a waxy layer tentatively identified as Japan wax. Prosser‐moulded bead type 9 was coloured by means of a chrome–tin pigment, while a combination of Mn and Fe is responsible for the black colour of the type 47 beads. Cuprite is most likely responsible for the red hue of glass layers from type 14. The dark palm green exterior of the type 17 bead was produced by using a combination of Cu and Fe compounds; iron was the only chromophore detected in the Indian red decoration. Copyright © 2017 John Wiley & Sons, Ltd.

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

“…Micro‐Raman spectroscopy carried out on the dark blue glass revealed the presence of different silicate bands in most samples: 170, 229, 329, 415, and 467 cm −1 in sample 7; 374, 1,062, and 1,129 cm −1 in sample 11; 274, 383, and 397 cm −1 in sample 12; and 195–196, 245, 309, 327, and 354 cm −1 in sample 14 (Figure c). As previously mentioned, these silicate bands are most likely the result of the rearrangement of the silicate network following selective leaching .…”

“…Micro‐Raman spectroscopy has been increasingly used in the study of glasses and glazes . As a first approach, the Raman spectrum of glass can be described as the signature of the SiO network, being characterized by the presence of two massifs corresponding to the bending and stretching modes of the SiO bonds, centered at approximately 500 and 1,000 cm −1 , respectively.…”

“…The proportion of Q n units and their wavenumbers have also been found to provide indirect information regarding the type and amount of glass modifiers (e.g., Na, K, and Pb) found in the glass . Moreover, the confocality and micrometric space resolution of micro‐Raman spectroscopy also allow the identification of inorganic compounds dispersed in the glassy matrix and responsible for its color and opacity …”

Recent advances in linear and nonlinear Raman spectroscopy. Part XII

“…The full characterization of the materials, including glassy network, opacifiers, and colorizers, was achieved by the combination of data from handheld X‐ray fluorescence, variable pressure SEM coupled with energy‐dispersive X‐ray spectrometry, micro‐FTIR spectroscopy and pyrolysis coupled to gas chromatography and mass spectrometry. The obtained chemical information was used to fill the existing gap in the chemical study of beads from western Central Africa . Veneranda et al characterized archaeometallurgical artefacts by means of portable Raman systems to study corrosion mechanisms influenced by marine aerosols.…”

GeoRaman

“…This paper focuses on possible difficulties that are encountered during in situ Raman measurement of Patagonian prehistoric rock art and some possible improvements. Coccato et al applied Micro‐Raman spectroscopy and complementary techniques (hXRF, VP‐SEM‐EDS, μ‐FTIR and Py‐GC/MS) to the study of beads from the Kongo Kingdom (Democratic Republic of the Congo). Li et al investigated the smoked murals in Mogao Grottoes by confocal Raman spectroscopy.…”