This study examines the mineral and proximate composition of three periwinkle species shells endemic to Nembe mangrove swamp for their potential use in soil amendment. 150 periwinkle shells of three different varieties were harvested and their proximate and mineral compositions were determined (following standard procedures) in Biochemistry Lab. Federal University Otuoke. The results reveal morphological diversity and cultural relevance of the periwinkle shell varieties – Tympanotonus radula (Imoron), T. fuscatus (Emoru), and Pachymelania aurita (Buhari). Significant variations (p ≤ 0.05) in their fiber, ether extract, crude-protein, and mineral content were observed. T. fuscatys exhibited the lowest moisture content (35.51 ± 1.31) and the highest dry matter (561.87 ± 0.63), whereas T. radula showed the opposite trend. T. fuscatus also recorded the highest crude fiber (4.68 ± 0.41%) and crude protein (25.00 ± 1.09%), while P. aurita had significantly lower values in both categories. In terms of mineral composition, T. fuscatus contained significantly higher (p<0.05) level of calcium, potassium, and magnesium than T. radula and P. aurita, making it particularly suitable for soil amendment and crop biofortification. T. radula had the highest phosphorus content (3.86 ± 0.18), whereas iodine concentration was highest in T. fuscatus (6.90 ± 1.05). The study concludes that periwinkle shells, especially those of T. fuscatus, hold significant potential for enhancing soil fertility and improving crop yields as natural soil amendments. This approach will not only support sustainable agricultural practices but also enriches the nutritional quality of crops.