jade, jadeite, fei cui, treated jade, FTIR, B jade, gems, SEM

Scanning electron microscopy (SEM) is investigated as a means of distinguishing untreated fei cui from acid-bleached and polymer-impregnated material by examining surface texture and electrical charging. Twelve polished green specimens, comprising four naturally coloured cabochons and eight treated pieces, were tested with conventional gemmological instruments; two weathered rough pebbles were additionally examined for fluorescence characteristics. Selected polished surfaces were then studied by SEM. All twelve polished specimens gave spot refractive indices around 1.66 and displayed similar visible absorption spectra, including the characteristic band at 437 nm, so these observations did not distinguish treatment. Most treated specimens floated in a heavy liquid of specific gravity 3.32, but two sank, as did all four untreated cabochons. Long-wave ultraviolet fluorescence also proved inconclusive: treated pieces showed variable chalky blue or yellow reactions, with one remaining inert, while naturally weathered material fluoresced strongly along altered edges and fractures. Ordinary microscopy generally revealed a cracked or spiderweb-like surface in treated specimens, but a very fine-grained example lacked this appearance. SEM examination showed that untreated fei cui possessed a compact interlocking microgranular structure, with grain boundaries remaining closely joined even at 2000× magnification. Treated specimens exhibited widened, etched grain boundaries, fractures and surface defects, more clearly resolved than under a gemmological microscope. Granular material could resemble a dried mudflat, while fibrous material displayed a looser texture with conspicuous gaps. Polymer accumulated in these spaces produced intense electrical charging during scanning, recorded as bright white lines outlining grains and filling fractures. This response was distinguished from the weaker, cloud-like white patches caused by surface wax. The fine-grained treated specimen required 500× magnification to reveal widened intergranular boundaries that were unresolved at 150× and undetectable with conventional optical examination. Tilting specimens improved the visibility of diagnostic surface features at magnifications between 150× and 500×. The authors conclude that SEM can provide useful confirmation of bleaching and impregnation, complementing other identification methods, including infrared spectroscopy. Although instrument cost and limited access restrict routine application, they report that a suspect specimen can be identified in under ten minutes and suggest that additional elemental analysis could further improve discrimination.