Avaliação da alterabilidade química de quartzitos ornamentais do Estado do Ceará

Abstract

This study aimed to carry out the petrographic characterization and the evaluation of the chemical alterability of two ornamental quartzites widely used in the state of Ceará: Perla Santana and Bianco Supreme. The research is framed within the context of the growing economic importance of the ornamental stone sector in Brazil, especially quartzites, which have been gaining prominence in the international market due to their high added and aesthetic value. Considering that the durability and aesthetic performance of these rocks are directly related to their resistance to chemical agents, this study seeks to understand how mineralogical, textural, and petrographic characteristics influence surface degradation processes. The methodology consisted of selecting representative samples, on which macroscopic petrographic analyses were performed, as well as tests of resistance to chemical attack and staining using different chemical reagents and everyday products. Thin sections were prepared, and color and gloss measurements were carried out at the UFC Geology Laboratory in Fortaleza, while petrographic and chemical analyses were conducted at the UFC Crateús’s campus laboratory. Color variations were quantified by colorimetry using the CIE L*a*b* system, and surface gloss was measured before and after chemical attacks, allowing an objective assessment of surface degradation. The results indicated that Bianco Supreme quartzite presents a more homogeneous texture, more compact structure, and lower density of fractures and accessory minerals, whereas Perla Santana shows a higher degree of fracturing and the presence of minerals filling fissures, which increases its susceptibility to fluid percolation and chemical action. Tests demonstrated that, in general, brushed surfaces are more susceptible to staining and gloss loss than polished surfaces. It is concluded that Perla Santana quartzite is more chemically vulnerable than Bianco Supreme, mainly for microstructural rather than purely compositional reasons, highlighting the importance of integrating petrographic characterization and technological tests for the proper specification and use of these materials in architectural projects.