ANALYSIS OF LATE BRONZE AGE GLASS AXES FROM NIPPURuA NEW COBALT COLOURANT

A multidisciplinary study of a unique group of Late Bronze Age (LBA) ceremonial glass axe heads and other artefacts shows that these are the first significant group of glasses coloured with cobalt to be identified from the Near East. The axes were excavated from the site of Nippur, in present-day Iraq. Several are incised with the names of three kings, which dates the material to the 14th13th centuries bc. Analysis by laser ablation inductively coupled plasma mass spectrometry (LAICPMS) indicates that the glass had high magnesia (MgO) and potash (K2O) associated with a plant-ash flux and was coloured blue by copper or a combination of copper and cobalt. These glasses are similar, but not identical, in major element composition to blue-coloured glasses manufactured in ancient Egypt and elsewhere in Mesopotamia in the same period. However, the Nippur cobalt- and copper-coloured glasses exhibit significantly different trace elemental compositions compared to Egyptian glass coloured with cobalt, showing that the ancient Near Eastern glassmakers had clearly identified and utilized a distinctive cobalt ore source for the colouring of this glass. Since it was previously thought that the only cobalt ores exploited in the LBA were exclusively of Egyptian origin, this new finding provides new insights on the origins of glass and how it was traded during the Bronze Age period.