Red pigments in the bronze age burials in the North Caucasus: complex analysis for identification of pyroprocessing of iron minerals

Ochre is a natural pigment of yellow or red color, mainly consisting of iron minerals. Along with determining the origin of mineral dyes, one of the main problems of studying natural pigments in archaeology is identifying the origin of the so-called “red” ochre, made on the basis of hematite. Hematite is a widespread mineral found everywhere. However, it can be obtained by pyroprocessing goethite, which is the main component of the “yellow” ochre. To test the hypothesis of the red ochre production through the pyroprocessing of iron oxides, 3 samples of ochre from the burials of the Bronze Age in the Republic of Adygea and the Krasnodar area have been studied. To identify the traces of thermal treatment of the raw ochre, we’ve carried out complex analysis, including the X-ray diffractometry, element analysis, infrared spectroscopy and microstructure analysis. The traces of the pyroprocessing have been revealed in the ochre sample from the burial of the Early Bronze Age near the Kazanskaya settlement. The form and size of the hematite crystals in the burial of the Ladozhskaya settlement indicate the unperformed heat treatment and the endogenous origin. The sample from the Novosvobodnaya village shows the traces of pyroprocessing, but the pigment’s microstructure indicates the sedimentary origin of the iron minerals from which it is composed. It’s been found that the color of pigments does not depend on the percentage of iron in the raw material sample. The presence and the ratio of hematite and goethite in the pigment, as well as the composition of other minerals in the final product are the most significant discoveries. P.I. Kalinin has carried out the complex analysis of pigment properties, data interpretation, literature review and paper writing; V.A. Trifonov has determined the archaeological context, interpreted the data, edited paper and approved the final version; N.I. Shishlina has provided samples for analysis, interpreted the data, made fundamental editiond to the paper; A.O. Alekseev has interpreted the mineralogical analysis and made certain amendments.