An extensive micro-Raman spectroscopic study of prehistoric paintings found in open air rock shelters at the Sierra de las Cuerdas (Cuenca, Spain) was carried out. In situ optical microscopy, petrological polarized light microscopy, scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDX) were used as auxiliary techniques. Haematite (a-Fe 2 O 3 ) of three granular types was the pigment that was most frequently encountered alone and in admixture with non-stoichiometric iron oxyhydroxides. A white pigment, but rarely used, results from a combination of white earths (a-quartz, anatase, muscovite and illite) and calcined bones (apatite); the presence of calcined bones also appears frequently in the red pigmented pictographs. The presence of significant amounts of charcoal underlying the white paint is suggestive of previous sketching on the shelter walls. Accretions of whewellite and weddellite resulting from the activity of fungi or lichens (e.g. Verrucaria nigrescens) are present in the painting panels, and carotenoids from this biological colonization were detected on several pictographs. The crystallization of gypsum and barytes in spallating areas of the painted surfaces is associated with sandstone weathering processes. An unusual deterioration of the art work caused by electric welding splashes resulting from the erection of protective ironwork grilles around the rock art panels was also detected.

Selected pictographs from the prehistoric painting panel 2 of Cueva del Tío Modesto shelter in the Sierra de las Cuerdas (Henarejos, Cuenca, Spain) were studied by Raman microscopy in order to determine the chemical composition of the pigments used. Hematite (a-Fe 2 O 3 ) was found as the main component. The hematite particle size of one motif is much smaller than that observed for the others. No binders were found. A blue-greyish crust extends over the whole panel. Whewellite, weddellite and amorphous carbon were identified in this crust. The Triassic sandstone on which the paintings are made is found to suffer from a flaking process. Therefore, flakes of the rocky substratum were studied, and a-quartz, whewellite, magnetite and gypsum were found. A micro-stratigraphic study of the flakes revealed channels of gypsum from one side of the flake to the other. This result supports the mechanism proposed for this sandstone weathering process.

The third painted panel of the Hoz de Vicente rock shelter (Minglanilla, Cuenca, Spain) contains a series of prehistoric pictographs which were studied by Raman microscopy. Scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX) and petrographic polarised light microscopy were used as auxiliary techniques. The results obtained indicate that well-crystallised haematite (α-Fe 2 O 3 ) of grain size less than 1 µm was used as red pigment. However, amorphous carbon, probably vegetable charcoal or soot, was used as the black pigment. A patina of whewellite and weddellite covers the areas of the painting panel with pictographs. The microstratigraphic study of a schematic figure revealed that the layer of pigment is sandwiched between layers of these hydrated forms of calcium oxalate produced by the activity of fungi and lichens. These products have also been detected in the layer of pigment. These findings will enable obtaining limiting radiocarbon 14 C accelerator mass spectrometry (AMS) dates for the corresponding pictorial events. On the other hand, crystallisation of gypsum in the external layers of the panel is related to the deterioration observed in the flaking areas. Gypsum and clayish minerals appear as the main components of an ochre-coloured accretion covering several parts of the panel.

Significant paintings from the Tito Bustillo (Ribadesella, Asturias) and El Buxu (Cardes, Asturias) caves, renowned archaeological sites of the Cantabrian Palaeolithic cave art, were studied by micro-Raman spectroscopy. Auxiliary techniques like infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and scanning electronic microscopy combined with energy dispersive X-ray spectrometry were also applied. Haematite (a-Fe 2 O 3 ) of three granular sizes (<1, <10 and <30 mm) is the main red component of these paintings. Wüstite, amorphous carbon, and Mn are additional components of some pigments. Hydroxyapatite was also detected in one pictograph. Calcite, a-quartz and clay minerals are used as filler materials. Particles of anatase are present in some cases. No organic binders were detected. Considering the main components, granular size, and secondary phases with Ni and Mn in the pigments it is concluded that the ochre quarry in the Tito Bustillo cave was not used to make the pigments of the selected paintings. Two figures of this cave seem to have been painted with a similar pigment. A possible relationship between paintings of both caves is discussed.

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