Colour and composition of nodules from the Calabrian clay deposits: apossible raw material for pigments production in Magna Graecia

摘要

Pliocene clays in Rocca Imperiale (North Calabria - Italy) and Monasterace (South Calabria- Italy) have oxide and hydroxide iron nodules of a range of colours, varying from brown to red. It is likely that the inhabitants of some colonies in Magna Graecia (who already used the clay deposits to produce bricks) had detected the presence of the above-mentioned raw materials and decided to use them to produce mineral pigments and to decorate polychrome artefacts. The nodules were pulverized and analysed through SEM-EDS, XRPD andcolorimetric analysis; further, they were heated at 275°C, 400°C, 550°C e 750°C, monitoring their mineralogical and chromatic transformations. Our study pointed out that it is possible to chemically differentiate the nodules of Monasterace from the nodules of Rocca Imperiale. Furthermore, our study proved that it is possible to produce mineral pigments by using such raw materials.