The South Khorasan region, as one of the principal settlement zones of the Parthians in ancient Iran, preserves significant evidence from this period, including numerous archaeological sites and cultural remains. During road construction operations in the areas of Kal-Jangal and Neh Castle- Nehbandan, several large Parthian pottery jars—mostly fragmented or partially preserved—were discovered. Given the dual function of such jars in antiquity, especially during the Parthian era (grain storage and funerary uses), this research employs a descriptive-analytical methodology and archaeometric approaches to address the following core question: What is the mineralogical provenance of the clays used in the pottery shards recovered from Nehbandan and Khosf sites, and, based on elemental analyses, what can be determined about their functional use? To address these questions, petrography, ESM, EDS, and soil analyses were performed on selected samples, including four semi-fragmented sherds from Kal-Jangal and two samples from Neh Castle in Nehbandan (under official license from the South Khorasan Cultural Heritage Organization). Due to the destructive nature of some analyses, only damaged and non-intact fragments were utilized. The results reveal the presence of tubular fibrous structures, a high carbon content, and low nitrogen on the inner surfaces of the pottery, all pointing towards their primary function as grain storage vessels. Overall, both mineralogical indicators and elemental data highlight a selective procurement of raw materials and technological adaptation in pottery manufacture, reflecting the economic and cultural needs of Parthian communities in South Khorasan.