<p>A surface micromorphology study of quartz grains was conducted using Scanning Electron Microscopy (SEM) to examine their surface features and assess the chemical influence of the depositional environment. Detrital quartz samples from the Sehib Early Eocene sandy phosphate deposit in Gafsa, southern Tunisia, exhibit surface microtextures associated with weathering processes. Three main categories of quartz alteration were identified based on diagenesis: (i) inherited climate-related weathering; (ii) transport weathering and hydraulic abrasion; and (iii) post-depositional chemical weathering under marine influence. The co-occurrence of quartz grains and francolite within the depositional environment promoted significant chemical dissolution of the quartz grains. The geochemical characteristics of this environment, particularly the concentrations of fluorine and organic matter, are interpreted as primary drivers of quartz grain weathering and dissolution. This process is evidenced by the development of etch pits that progressively developed into complex networks of crevasses and grooves. Other microtextures, such as V-shaped percussion cracks, are interpreted as features resulting from mechanical transport that was later overprinted by post-depositional chemical dissolution. Overall, quartz grain weathering appears to be controlled by a combination of geological and chemical parameters that accelerate or decelerate the dissolution process.</p>