Micro‐Raman spectroscopy on pigments of painted pre‐Islamic ceramics from the Kur River Basin (Fars Province, Iran): The case of manganese oxides identification

Abstract

Micro-Raman spectroscopy was used for the analysis of painted pre-Islamic ceramics from the Kur River Basin (Fars Province, Southwest Iran). A total of 21 sherds were analysed dating from the Neolithic to the Late Bronze Age and belonging to different ceramic wares and sites. The main focus of this research was to identify the pigments used for the red and black decorations of the different ceramic wares from the Kur River Basin and to elaborate on the manganese identification and their differentiation through Raman spectroscopy.Haematite (α-Fe 2 O 3 ) and manganese oxides could be identified as the main compounds for the decoration in the different ceramic wares, except for the Bakun ware in which also carbon black could be determined as a probable pigment for black decoration using micro-Raman spectroscopy. The identification and discrimination of manganese oxides were a meticulous task due to the sensitivity of these materials to the laser power, which can provoke degradation. Nevertheless, Raman spectroscopy was successfully applied for the identification of spectral patterns of the ceramics and their attribution to several manganese oxides present in the decorative mixtures, such as jacobsite (MnFe 2 O 4 ), bixbyite (α-Mn 2 O 3 ) and hausmannite (Mn 3 O 4 ). K E Y W O R D Sceramics, Jacobsite, Kur River Basin (Iran), manganese oxides, red and black pigments

Identification of tunnel structures in manganese oxide minerals using micro‐Raman spectroscopy

“…However, with similar chemical properties, substitution of magnesium should also be taken into account as it can be incorporated into the crystal lattice relatively easily. Its effect is a shift in Raman band position towards lower wavenumbers, that is, ~600 cm −1 33,43 . Therefore, we suspect that the sample we have characterized as jacobsite would contain a significant amount of magnesium and can be labelled as Mg‐jacobsite.…”

“…Jacobsite is interesting from an archaeological perspective due to its specific use. For example, it has been used as a pigment for applying dark coloured decoration on pottery 33,44,45 . The specific pigment used can come from natural jacobsite, but it can also be derived synthetically by combining a manganese oxide, for example, pyrolusite, with an iron oxide phase, such as haematite (α‐Fe 2 O 3 ).…”

“…30 Many researchers have encountered these pigments when studying historical artefacts. [31][32][33] Correct characterization of the different phases of manganese oxides is thus of great importance. Using a variety of techniques, identification of Mn oxides has been reported on natural mineralogical samples 29,[34][35][36] as well as synthesized ones.…”

“…Thus, by applying greater laser power and/or measuring time, degradation effects and/or transformation of phases can occur, which ultimately can hamper the correct identification of the unknown manganese oxide phases. 29,34,35 Nonetheless, Raman spectroscopy has been successfully applied for the identification of manganese oxide materials in the archaeometry field, 33,[43][44][45] as well as in the industrial applications 23,27,28 and the extra-terrestrial context. 39 Mulè et al in 2017 made an automated curve fitting and unsupervised clustering of manganese oxide based on the Raman response of samples.…”

On the use of a zoom lens for remote Raman measurements: Application in cultural heritage research

“…Raman spectroscopy is well appreciated for the molecular spectroscopic analysis of a broad range of art objects, [1,2] such as mediaeval manuscripts, [3,4] rock art, [5,6] wall paintings, [7,8] ceramics, [9,10] easel paintings, [11,12] etc. This approach has many advantageous features for applications on the investigation of cultural heritage objects, such as the ability to quickly obtain a molecular spectrum of inorganic as well as organic molecules.…”