Mineralogical investigations of Raʾs al Jinz 2 bitumen (Jaʿalān, Sultanate of Oman)

• Published in: Proceedings of the Seminar for Arabian Studies Vol. 44; pp. 25 - 34
• Main Authors: Badel, Émilie, Kramm, Ulrich
• Format: Journal Article
• Language: English
• Published: Archaeopress 01-01-2014
• Subjects: Bitumens; Boats; Calcite; Caulking; Geology; Lagoons; Minerals; Olivine; Sedimentary rocks; Weathering processes
• ISSN: 0308-8421

A high number of bituminous pieces have been discovered at the archaeological site of Raʾs al-Jinz 2 (Jaʿalan province, Sultanate of Oman). They are dated to the second half of the third millennium BC (Cleuziou & Tosi 2000: 27-28, 63-66). The bitumen is thought to come from natural seeps in northern Iraq (Connan et al. 2005: 61). It was later processed by melting it and adding some minerals and crushed vegetal remains. It has been demonstrated that such artificial mixtures were used at least for caulking seagoing boats (Cleuziou & Tosi 1994). Regarding bitumen processing and its inorganic content, previous studies document high concentrations of minerals (Connan et al. 2005: 38—40; Rinaldi & Tosi 2008). Thanks to X-ray diffraction analysis, a few of them were broadly identified (Connan et al. 2005: 39, fig. 12, table 6). Nevertheless, a substantial part of this mineralogical content still remains unknown and the nature of the temper itself was not clearly identified, nor was its provenance. The first results of our study show that this content is made of a heterogeneous assemblage of minerals, which vary according to grain size, origin, weathering, and their own associations. Some minerals do not come from an original temper and originate in any adventitious aeolian deposit and grains sticking to the bitumen during its processing and lifetime use, or are even the result of post-depositional alterations at the site. Among these, however, a recurring mineralogical pattern has been widely identified in RJ-2 samples, which is a sedimentary rock of the silt-size fraction. Some minerals associated to this matter, for instance the olivine-chromite association characteristic of peridotites from ophiolites, help define a geographic area within which it could have been collected.