The chemical-mineralogical characterization of rupestrian paintings in red, white, black and yellow colors, which decorate the rocky walls from the archaeological sites of Ema and Furna dos Índios (Inhuma, Piauí, Brazil) was performed. The chemical analyses were performed in situ by the non-invasive analytical technique X-ray fluorescence spectrometry (XRF) as well as in laboratory using a non-destructive approach, without previous sample preparation, and Raman microscopy, and scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) techniques. The results, when together, allowed unequivocal identification of the main substances responsible for the color pigments, namely, hematite (red pigment), gypsum (white pigment), amorphous carbon from charcoal (black pigment) and goethite (yellow pigment).

Instrumental advances have been employed in the study of archeological remains such as prehistoric rupestrians paintings with the objective of chemically characterizing them in order to reconstruct the cultural technologies of a prehistoric human group and/or to support conservation science studies. The analytical techniques most commonly used in archaeometric research are non-destructive or semi-destructive and preferably portable to preserve the integrity of the rupestrians paintings. They include X-ray Fluorescence Spectrometry (XRF), Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM/EDS), Raman spectroscopy, X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Laser-induced Breakdown Spectroscopy (LIBS), and the many techniques with emerging applications such as Mössbauer Spectroscopy, X-ray Absorption Near Edge Structures (XANES), Particle Induced X-ray Emission Spectrometry (PIXE) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA ICP-MS). Therefore, this paper presents a review of the literature on the development of chemical strategies employed in the study of rock art, focusing mainly on the critical evaluation of analytical techniques used, limitations, challenges and the perspectives within this area of study.

Phosphorus (P) is an important chemical marker of the past human presence, because, besides indicates the localization of possible archaeological sites, also, contributes to clarify doubts regarding to origin, duration and to specific functions that were developed in them. The present study aimed to obtain a simple, accurate, fast and non-destructible analytical method to determine phosphorus in sediment samples of the Toca da Baixa dos Caboclos archaeological site, an enclave of the Serra da Capivara National Park, Piauí, Brazil. For the proposed method, a portable energy dispersive X-ray fluorescence (p-ED-XRF) equipment and cross calibration to sample direct analysis were used. The results show that the concentrations obtained by the proposed method, cross calibration with use of p-ED-XRF, and by the spectrophotometric method were considered statistically equal, when compared by the paired t test (p=0.05). By its turn, the intermediate accuracy and recovery tests showed values in the range of 2.41−3.56% and 85.10-102.66%, respectively.