RED PALAEOLITHIC PIGMENTS: NATURAL HEMATITE OR HEATED GOETHITE?*

Abstract

Yellow goethite (α‐FeOOH) and red hematite (α‐Fe203) were used as pigments by Palaeolithic painters. When heated, goethite dehydrates and transforms to hematite Archaeologists wonder whether prehistoric people knew of this property and used it. We present a way to distinguish heated goethite from natural hematite. The methods used are X‐ray diffraction and transmission electron microscopy. A double ‘signature’, namely selective broadening of diffraction reflections and porous nanostructure, is evidenced in heated goethite. Coupled with mineralogical associations, this allows us to establish a procedure to investigate the natural or artificial origin of hematite samples. Applied to the Palaeolithic site of Troubat, it reveals no difference between the Magdalenian and Azilian cultures concerning the heat‐treatment of pigments; an area specializing in heat‐treating pigments, may, nevertheless, have existed inside the cave, which would indicate that heating wax deliberate.