On the Origin of the Green Colour of Archaeological Bone Artefacts of the Gallo‐Roman Period

Abstract

International audienceRecent findings in the city of Reims have lead to the discovery of manufactured bone objects coloured in green throughout their entire volume. In order to discover the intentional nature of the colouration and to propose a colouration mechanism, modern ox bones have been coloured in the laboratory. Bones with a hue similar to that of the archaeological artefacts have been obtained by boiling in an acidic brine in a copper vessel. A combination of infrared spectroscopy, X-ray diffraction and transmission electron microscope observations did not reveal the speciation of copper, but allowed us to validate the colouration process and to discuss the intentional origin of the colouration

The girl with the chariot medallion: a well-furnished, Late Iron Age Durotrigian burial from Langton Herring, Dorset

“…Areas of bright green patination with a bluish tinge in places were present on various bones of the upper body ( Figure 3a and Figure 3b). Such staining is generally held to result from contact with copper or copper alloy objects in the burial environment, as confirmed chemically by several studies (Hopkinson, Yeates, and Scott 2008;Ferrand et al 2014). Green staining on bone can also be caused by the growth of algae or moss (Dupras and Schultz 2013), although such organic causes are less likely in buried environments where the bone is not exposed to light.…”

Materiality and Object Design and Function: Perspectives from Artefacts

“…89 See Flecker, and Engels, this volume; above, on marbled glass; Bradley 2009, 87-110 on imitation of materials more widely. 90 In another example, extant green-dyed bone objects can be shown to have been dyed using copper oxides, and so had an even more similar appearance to copper objects which had developed verdigris: see Ferrand et al 2014. They were probably made as deliberate imitations of such antique objects.…”

“…As with the vessels, verdigris-covered metal furniture or fittings for furniture may have been valued since the oxidised coating indexed the furniture's antiquity. There is some evidence of furniture with green-dyed hinges (from Pompeii, for example: see Ferrand et al 2014Ferrand et al , 1038, which could have been successfully used to mimic antique furniture: see Swift 2021. Such vessels in copper alloy would presumably have been employed for display purposes rather than actual use, unless the interior was kept free of oxidation through assiduous cleaning; similar vessels in ceramic were more practically useful, while still conforming to an aesthetic that valued the aged appearance of antique bronze.…”