Oxidation states of iron as an indicator of the techniques used to burn clays and handcraft archaeological Tupiguarani ceramics by ancient human groups in Minas Gerais, Brazil

Iron Forms Fe(II) and Fe(III) Determination in Pre-Roman Iron Age Archaeological Pottery as a New Tool in Archaeometry

“…The differences in the material from which the ceramics are made are not reflected in the iron speciation. According to the literature data, the presence of Fe (III) and Fe (II) forms and their Fe(III)/Fe(II) ratio reflect the technology of the ceramics production process [ 18 ], particularly the temperature and conditions of the ceramics firing process [ 31 ]. Thus, it can be concluded that, regardless of the origin of the ceramics tested, and, therefore, the material (clay) from which it was made, two groups of ceramic objects ( Figure 3 ) stand out on the basis of iron speciation, probably as a result of similar technological processes.…”

“…Ceramics as works of art are often painted on the surface. There are numerous examples of element speciation studies in ceramics in which the oxidation state of the elements was the subject of determination: iron and manganese in Sicilian “proto-majolica” pottery [ 15 ], iron in black glaze of Chinese pottery [ 16 ], cobalt in Chinese porcelains from the 16th to 17th century [ 17 ], and iron in ceramics from Brazil [ 18 ].…”

“…Iron is an element that is the component of many silicate minerals, such as illite, chlorite, glauconite, or biotite [ 19 ]. The determination of iron speciation in pottery is especially important because various types of clay, just like different clay firing techniques and temperatures, have a major influence on the oxidation state and—furthermore—on the colour of ceramics [ 18 ]. Fe(III) is responsible for an orange-red colour, whereas Fe(II) imparts a dark grey colour.…”

“…One of them uses Mössbauer spectroscopy, which is based on the Mössbauer effect. It was applied in the recognition of the oxidation state of iron in Brazilian ceramic samples, along with Scanning Electron Microscope (SEM), X-ray fluorescence (XRF), and X-ray diffraction (XRD) [ 18 ].…”