gems, jade, nephrite, archaeogemology, forensic science, gemology, Raman spectrscopy

Jade (Figure 23.1) is a precious and intrinsically beautiful material that has been used in China for more than 7,000 years. In modern mineralogical usage, the term “jade” refers to two minerals, nephrite, an amphibole mineral, and jadeite, a pyroxene. Nephrite was used almost exclusively in ancient China until the eighteenth century, when jadeite from Burma was first imported, so that the distinction between these two types is particularly important. In antiquity, a wide range of other minerals and even artificial materials, sometimes referred to collectively as “Beautiful Stones,” were used alongside “true jade.” Identification of these is essential to establish the range of simulants that were used to make ancient artefacts. A further reason for analysis is that antiquities made from jade are highly prized, so that there has always been a strong incentive to use less precious substitutes; analysis may sometimes be required to assist in the assessment of authenticity. Finally, there is increasing interest in determining the sources used to make jade artefacts in ancient China, involving the characterization of jade artefacts and comparison with potential sources for the nephrite jade. Studies of this type may provide data that is also relevant to questions of authenticity. Precisely because jade artefacts are so highly regarded, the removal of samples for scientific examination is frequently unacceptable, making investigations of the sort outlined above very difficult. The advent of Raman microscopes such as the Dilor LabRam Infinity (Jobin Yvon Ltd., Stanmore, UK) used in this study offered the possibility of beginning to address these questions. The jade minerals, nephrite and jadeite, and also the wide range of simulants and substitutes, each give characteristic Raman spectra, permitting their unambiguous identification. Moreover, the analysis can be carried out directly on the artefact, without the need to remove a sample; it is non-destructive and non-invasive.