This study provides the first comprehensive mineralogical and geochemical characterization of the economically significant Doust Abad bentonite deposit in the Ferdows region of eastern Iran. Results reveal a high-purity, stratabound deposit dominated by Na-montmorillonite (>75% of the clay fraction), alongside cristobalite, quartz, and minor amounts of zeolites (e.g., clinoptilolite) and gypsum. Bulk-rock geochemistry, marked by high SiO₂ and depletion of mobile cations, indicates an intense alteration of a felsic volcanic precursor. This is consistent with the calc-alkaline, rhyolitic to trachyandesitic volcanism of the Eocene–OligoMiocene Lut Zone. The exceptional purity, Na-montmorillonite dominance, and low heavy metal content position the Doust Abad bentonite as a high-quality raw material, suitable for traditional and advanced industrial applications, including environmental remediation, catalysis, agriculture, pharmaceuticals, and nanocomposites.

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