Identification of the gemstone jet.

Jet is a mineraloid that is found across the world and has been used as a gemstone since antiquity to make jewellery. Authenticating jet is difficult and most methods result in damage. There are circumstantial diagnostic tests for so-called ’true-jet’: when rubbed against unglazed porcelain, true jet will leave a brown streak, although there are other materials that will also do this. As it is basically coal, jet will burn with a sooty flame. For historical artefacts, such methods are clearly unacceptable and there is a need for a viable non-destructive technique that can examine a complete object. Inelastic neutron scattering spectroscopy offers a potential solution. The technique is non-destructive, relatively large (several cm) samples can be measured, it is a bulk measurement, sample preparation is trivial and the entire “infrared spectroscopy” 0-4000 cm-1 range is obtained.