Radiocarbon Dating of Iron Artifacts

Abstract

During the late 1960s, N. J. van der Merwe (1969) obtained 14C measurements on 11 iron pieces, ranging in carbon content from medium carbon (0.22%) wrought iron (1.2 kg used) to high carbon (3.2%) cast iron (30 g), thereby demonstrating the feasibility of the technique for 14C dating iron. In the early 1980s, Sayre et al. (1982) repeated two of van der Merwe's measurements, and carried out two analyses on a recently rediscovered Elizabethan(?) iron bloom. Thirty grams were required of this medium carbon wrought iron to obtain an age using small proportional counters. A number of iron artifacts have recently been analyzed by accelerator mass spectrometry (AMS) at IsoTrace. Samples ranged in size from 3.4 g of a medium carbon (≃0.4%) wrought iron bloom to 274 mg for a high carbon (1.79%) wootz steel fragment. AMS now permits analysis of samples that previously were too small or too valuable to be analyzed. For larger samples, multiple analyses can reveal variations that may aid the evaluation of sample history.