Electron spin resonance spectroscopy has attracted attention as a potential dating method. This work reports preliminary investigations into the application of ESR dating to aragonitic shells and corals. The ESR spectrum of aragonite can be clearly idendified and is distinct from that of the other calcium carbonate polymorph, calcite. A potential dating peak has been identified that responds linearly to radiation and appears stable. Comparison of fossil coral results with uranium series dating gives good agreement. However, work on shells is complicated by the existence of significant signal strength in the dating peak in modern shells. This suggests the archaeological clock is not zero when the shell is formed, and that therefore extrapolated equivalent dose values may overestimate the radiation damage to the shell since formation.