This study presents a new approach for detection and mapping of ancient slag heaps using 16-band multispectral satellite imagery. Understanding the distribution of slag (a byproduct of metal production) is of great importance for understanding how metallurgy shaped long-term economic and political change across the ancient Near East. This study presents results of slag mapping in Oman using WorldView-3 (WV3) satellite imagery. A semi-automated target detection routine using a mixed tuned matched filtering (MTMF) algorithm with scene-derived spectral signatures was applied to 16-band WV3 imagery. Associated field mapping at two copper production sites indicates that WorldView-3 satellite data can differentiate slag and background materials with a relatively high (>90%) overall accuracy. Although this method shows promise for future initiatives to discover and map slag deposits, difficulties in dark object spectral differentiation and underestimation of total slag coverage substantially limit its use. Resulting lower estimations of combined user’s (61%) and producer’s (45%) accuracies contextualize these limitations for slag specific classification. Accordingly, we describe potential approaches to address these challenges in future studies. As sites of ancient metallurgy in Oman are often located in areas of modern exploration and mining, detection and mapping of ancient slag heaps via satellite imagery can be helpful for discovery and monitoring of vulnerable cultural heritage sites.

Soft-stone vessels (made of the rock chloritite, which is comprised of the mineral chlorite) are an important component of the material culture record of ancient southeast Arabia. Given the prevalence of soft-stone vessels in domestic and funerary contexts, and the natural geological occurrence of chloritite in the region, archaeologists have long suspected that soft-stone vessels could have been produced in United Arab Emirates (UAE) or Oman. However, over many decades of research very few pieces of worked raw material or unfinished vessel fragments have been recovered in Arabia. This changed dramatically in 2015 with the discovery of the Iron Age village of Aqir al-Shamoos where thousands of raw, worked, and unfinished pieces attest to softstone vessel manufacture. Aqir al-Shamoos continues to yield new insights regarding soft-stone vessel production, but the source of raw material used to craft these objects initially remained unknown as no natural chloritite deposits had been found in the immediate vicinity of the site. We present results of hyperspectral satellite imagery target detection used to search for natural surface occurrences of chloritite near Aqir al-Shamoos. Despite limitations in carbonate and phyllosilicate mineral discrimination, field survey of the satellite detection results revealed chloritite outcrops in the ophiolite formation mountains 1.4 km northwest of Aqir al-Shamoos near the newly discovered archaeological site of 'Waby al-Zady. Reflectance spectroscopy (0.35-2.5 μm) of material from multiple chloritite sources indicates that chloritite from 'Waby al-Zady is spectrally very similar to material at Aqir al-Shamoos but quite different in comparison with material from other locations. These findings indicate that: (1) hyperspectral satellite imagery target detection can be useful for chloritite prospection, (2) 'Waby al-Zady (or somewhere very nearby) was probably the source of chloritite used at Aqir al-Shamoos, and (3) chloritite reflection spectra may be useful for distinguishing chloritite from different sources.

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