Early Islamic torpedo jars from Siraf: scientific analyses of the clay fabric and source of Indian Ocean transport containers

This paper concerns Sasanian to Early Islamic period transport containers, usually lined with bitumen, known as Torpedo jars. Widely distributed throughout the western Indian Ocean, with outliers as far west as Egypt and to the east in Indonesia, they are an important marker of maritime exchange. Their area of production is thought to be central/southern Iraq or southwestern Iran, the latter in keeping with proposed bitumen sources in the region of Ilam/Khuzestan. Here thirteen Torpedo jar samples from Siraf (southern Iran), belonging to two class categories defined by form and macroscopic fabric, were analysed. The technology of manufacture and potential source areas were examined in thin section by polarising, digital and scanning electron microscopy. These same techniques were used to examine the bitumen layer, providing insight into the vessel lining process. Analysis generally validated the distinction between the two classes; fabric variation within the classes identified eight petro-fabrics, suggestive of at least five workshops. These results point to regionally related workshops for each class category, exploiting distinct clay resources, rather than two single production sites. Suitable clay resources are widely available throughout central/southern Iraq and southwestern Iran, including Ilam/Khuzestan.