Low-temperature nitrogen adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, as well as infrared spectroscopy were used to characterize structural features of raw and acid-treated saponite from Tashkiv deposit of Ukraine. It was determined that raw saponite is predominantly composed of trioctahedral saponite with an admixture of dioctahedral nontronite and associated minerals such as quartz, hematite, and anatase. Raw saponite clay was characterized by a high content of iron (19.3%) and titanium (1.1%). Iron is present in the form of hematite particles, isomorphic replacements in octahedral and tetrahedral sheets of a clay structure, or as a charge-balancing cation in the interlayer space. Titanium is homogeneously dispersed as submicrometer anatase particles. The porous structure of both saponite forms consists of micro-meso porous system with narrow slit mesopores dominating. As a consequence of the acid treatment, the specific surface area increased from 47 to 189 m² g⁻¹, the total pore volume from 0.134 to 0.201 cm³ g⁻¹, and the volume of the micropores increased sevenfold. Using the data of our research allowed us to utilize these mineral resources wisely and to process saponite more efficiently.