Archaeometric analysis of the "Jehoash Inscription" tablet

A gray, fine-grained arkosic sandstone tablet bearing an inscription in ancient Hebrew from the First Temple Period contains a rich assemblage of particles accumulated in the covering patina that includes calcite, dolomite, quartz and feldspar grains, iron oxides, carbon ash particles, microorganisms, and gold globules (1-4 μm in diameter). There are two types of patina present: thin layers of a black to orange-brown, iron oxide-rich patina, a product of micro-biogenetical activity, as well as a light beige patina mainly composed of carbonates, quartz and feldspar grains. The patina covers the rock surfaces and inscription grooves post-dating the incised inscription as well as a fissure that runs across the stone and several of the engraved letters. Accelerator Mass Spectrometry (AMS) analyses of the carbon particles in the patina yields a calibrated radiocarbon age of 2340-2150 Cal BP and a conventional radiocarbon age of 2250 ± 40 years BP. The presence of microcolonial fungi and associated pitting indicates slow growth over many years. The occurrence of pure gold globules is evidence of melting (above 1000 °C) indicates a thermal event. This study supports the antiquity of the patina, which in turn, strengthens the contention that the inscription is authentic.