Colourful earth: Iron-containing pigments from the Hellenistic pigment production site of the ancient agora of Kos (Greece)

The red, brown, yellow and green pigment lumps from the Hellenistic pigment production site of the ancient agora of Kos (Dodecanese, Greece) are the focus of this paper. A selection of pigments is examined through a combination of analytical techniques, including SEM-EDS on uncoated samples, X-ray powder diffraction, FTIR and pRaman spectroscopy. Through the study of raw pigments deriving from the context of a production site, the aim is to approach pigment manufacturing contextually during the Hellenistic period. The examined red pigments were characterised as red earths (rubricae, mu iota lambda tau omicron iota), with their colour primarily attributed to hematite. However, significant variance was observed in their chemical and mineralogical composition, reflecting on their final colour. Interestingly, two of the red samples contained lead tetroxide in addition to hematite. The colour of the brown pigments was attributed to a complex mixture of iron oxides. The chemical and mineralogical composition of the two yellow lumps showed that they are of different origin; the first, composed of goethite and quartz, can be characterised as a yellow earth (sil, omega chi rho alpha) and the second corresponds to the mineral jarosite. A green-coloured lump was characterised as a type of celadonitic rock. The variance in the composition of the examined pigments indicates the treatment techniques carried out at the site and the preferences of the local craftspeople. The finds from the Koan workshop illustrate the complex and sophisticated nature of pigment production, suggesting an intertwined relationship with mining and metallurgy.