Chert: From diagenesis and formation processes to industrial and ceramic applications

Porcelanite and chert are silica-rich sedimentary rocks composed of varying proportions of megaquartz, microcrystalline quartz, chalcedony, opal-CT, and opal-A. Both porcelanite and chert are characterized by their high silica purity, fine-grained texture, and distinctive porcelain-like sheen. Their scientific classification largely depends on the relative proportions of silica phases (opal-A/amorphous silica, opal-CT, cristobalite, tridymite, and quartz). Studying these materials is essential for reconstructing ancient sedimentary environments, understanding diagenetic processes including the general formation pathway involving the initial precipitation of amorphous silica followed by successive transformations from opal-A to opal-CT, then to cristobalite/tridymite, and ultimately to microcrystalline quartz, and tracing the evolution of the terrestrial biosphere. Furthermore, their diverse applications from archaeology to advanced technological industries make them subjects of multidisciplinary interest. This review aims to provide a comprehensive synthesis of current knowledge on silica-rich sedimentary rocks, with a focus on their formation processes, physicochemical properties, industrial uses, as well as ongoing scientific debates and future research directions. It also explores the main analytical techniques used (such as X-ray diffraction, chemical analysis, SEM, and optical petrography) in their investigation, highlights recent findings, and discusses the broader implications of these discoveries, particularly for the development of advanced ceramics, selected biomedical applications, wastewater filtration and treatment technologies, and innovations in the construction-material sector. As this work presents a synthesis of existing literature, no graphical abstract is provided.