Portable X‐Ray Fluorescence Spectrometry in the Investigation of Coastal Rock Art at the Pedra do Maçaranduba Site (Piauí, Brazil)

ABSTRACT This study aims to understand the composition and application of red rock art from the Pedra do Maçaranduba archaeological site, located on the coast of Piauí (Brazil). This is a pioneering study of archaeological rock art sites found in the coastal region of Brazil. The research combines the techniques of optical microscopy, x‐ray fluorescence spectrometry, and Raman spectroscopy. The results suggest, through these techniques, that the pigments were applied in a liquid form (suspension with more diluent than raw material) and that wear caused by saline efflorescence and natural weathering is the primary conservation issue for the archaeological heritage. X‐ray fluorescence measurements showed the highest percentages of iron, ranging from 4.3% to 19.4% (w/w), with the intensity of the pigment's color increasing in proportion to the iron content. In addition, elements such as silicon (Si), aluminum (Al), phosphorus (P), sulfur (S), potassium (K), and calcium (Ca) were detected, suggesting their presence is due both to the substrate and to materials added to the paint to enhance properties like fixation and consistency. Raman spectroscopy indicated that hematite (α‐Fe 2 O 3 ) is the main mineral component in the analyzed samples. These results enhance our understanding of prehistoric painting techniques and inform future conservation strategies for coastal rock art in Brazil.