R1: Characterization and description of minerals (Joint Session with The Gemmological Society of Japan)

12:30 PM - 2:00 PM JST(3:30 AM - 5:00 AM UTC)

[R1P-12] Mineralogical features of an iron-smelting slag from the Late Iron Age site of Tell Mastuma, northwest Syria

*Masanori KUROSAWA¹, Yuma Hanabusa², Shin’ichi Nishiyama³, Hidetoshi Tsumoto⁴ (1. Univ. Tsukuba, 2. Grad. Sch., Univ. Tsukuba, 3. Chubu Univ., 4. Ancient Orient Museum)

Keywords:

slag,iron smelting,Late Iron Age,SEM-EDS,Tell Mastuma

Microtextures and mineral compositions of an iron-smelting slag from the Late Iron Age site of Tell Mastuma, northwest Syria, were analyzed with a scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM-EDS) to elucidate the spread and regional variations of early iron-making technologies in the ancient western Asia. The analysis revealed that this slag consisted primarily of abundant wüstite crystals and glass, and is a typical iron-smelting slag with a partially heterogeneous composition. The smelting temperature, inferred from the combination of crystals present, was estimated to be between 1200 and 1300 degree. Furthermore, the absence of manganese in the slag and glass suggested that the raw material was likely not the Fe-Mn type of iron ore widely distributed across West Asia. The most notable feature was the presence within the slag of unmelted rock fragments, such as limestone and talc, along with localized regions rich in magnesium and calcium derived from these materials. This indicates that limestone, talc, and so on were intentionally added as fluxing agents to facilitate the smelting process. These rocks were readily available in the vicinity of the site and in neighboring geological bodies. Slag rich in CaO, produced by the addition of limestone, efficiently absorbs impurities such as phosphorus and is well-suited for producing high-purity iron. Indeed, phosphorus was well absorbed into the glass phase within the slag. This suggests that, as early as the Early Iron Age, the northwest Syria possessed advanced smelting techniques utilizing slag-forming agents and was producing high-quality iron with few impurities.