Since it was first excavated by Beno Rothenberg in 1965, Site 39B at Timna lies at the center of a controversial debate regarding its chronology. The excavator believes that the site and the copper producing installation located there were used in the Chalcolithic period and thus the installation constitutes the earliest example of its kind in the world. This determination has been called into question numerous times, among other things due to the 1st century CE radiometric dating from the walls of the installation, which the excavator contends is evidence of its secondary use.
As part of the current study the quality of copper slag was examined as a recorder of the intensity of the geomagnetic field. A series of experiments that were conducted on hundreds of slag specimens from twenty eight archaeometallurgic sites in Israel and Jordan produced unparalleled results in their quality and have demonstrated the highest percentage of success in comparison with experiments based on other materials (e.g. fired clay). The reliability of the material as an archaeomagnetic recorder made it possible for us to construct a dependable intensity change curve to the period limited to the time from the beginning of the appearance of metallurgy in human society, i.e. the past six thousand five hundred years. This curve is currently based on dates that were derived from an archaeological context and show acute and frequent changes in the strength of the geomagnetic field.
The archaeomagnetic results that were received from the slag specimens from Site 39B at Timna show three distinct and different groups of geomagnetic intensity. One group shows a high intensity (~77μΤ), compatible with the peak that was documented at the end of the Late Bronze Age and beginning of the Iron Age and indicative of metallurgical activity at the site combined with a broader picture of intensive activity in the entire region during the period under discussion. A second group shows a medium intensity (~48μΤ) that can match a number of time periods, among them the Early Roman period, which is represented at the site by the radiometric dating results. The third group shows a low intensity (~33μΤ) which is compatible with the low point that was documented in the Chalcolithic period and attests to metallurgical activity at the site during that time. If this is indeed the case, then the results of the experiments corroborate Rothenberg’s position representing a multi-period site that had its beginnings with the start of metallurgy in the Chalcolithic period.