The Bahabad zinc smelting site, located 71 km north of Bahabad in Yazd Province, Iran, spanning 220 m² within the Tabas-Posht-e-Badam metallogenic belt, is a key ancient metallurgical center. This study aims to identify the extracted metal, analyze metallurgical processes, and reconstruct the employed technologies through petrographic and geochemical analyses of ceramic nails and furnace slags. Thirty ceramic nails and 20 slag samples were collected, with five samples from each group selected for petrographic study and chemical analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES). Petrographic results revealed that the ceramic nails, made from fired clay, exhibit a porphyritic texture with ~20% quartz and minor calcite, while slags contain fayalite (Fe₂SiO₄), melilite, pyroxene, and wüstite (FeO), indicating high-temperature, reducing conditions. Chemical analysis showed an average of 1.21% ZnO in nails, confirming their role in collecting zinc vapors as tutia (ZnO) over centuries, and 3.74% ZnO in slags, suggesting incomplete zinc extraction. Low lead (669 ppm in nails, 315 ppm in slags) and sulfur (1053 ppm in nails, 361 ppm in slags) concentrations indicate the use of oxidized ores like smithsonite (ZnCO₃) or hemimorphite rather than sulfides like sphalerite (ZnS), consistent with the region’s oxidized lead-zinc deposits. Two-tier furnaces, with a lower heating chamber and an upper perforated clay plate holding ceramic nails (10–20 cm long, 2–4 cm diameter), facilitated upward distillation. This technology contrasts with India’s downward distillation (sphalerite, square furnaces) and China’s condenser-based upward method (rectangular furnaces), highlighting Iran’s indigenous innovation using charcoal and ceramic nails. The study underscores the technology’s adaptation to local conditions and its significance in global metallurgical history.
