[Research of genesis of black bands in Burma jadeite].

A kind of jadeite jade with black bands appeared in the mining area of Burma, which presents a gray-black to black appearance. X-ray powder diffraction analysis shows that the components of the sample are mainly jadeite and a small amount of omphacite. A large number of small, dark mineral inclusions were observed by SEM (scanning electron microscopy), distributed in the mineral grain gaps and tensional fractures of jadeite. These inclusions show specific peak at 1582 cm(-1) , and some of them also show a peak at 1346 cm(-1), indicating that these black inclusions are single crystal graphite and amorphous graphite, based on characteristic Raman spectra. These graphite inclusions forming different types of group lead to great light scattering loss in the range of 3000 nm to visible wavelength resulting in large transparency loss and cause the black band in sample. Two series of zircons were found in the sample by microexamination with high crystallinity and inconspicuous metamictization, as testified by Raman spectroscopy.

[Spectra of dark green jade from Myanmar].

Chemical compositions and spectral characteristics of one type of dark green jades assumed from omphacite jadeite from Myanmar jadeite mining area were studied by X-ray powder diffraction(XRD), X-ray fluorescence spectra(XRF), Raman spectra(RM) and UV-Vis Spectroscopy, etc. Based on testing by XRD and XRF, it was shown that it belongs to iron-enriched plagioclase, including albite and anorthite. The compositions range is between Ab0.731 An0.264 Or0.004 and Ab0.693 An0.303 Or0.004. Raman spectra of samples, albite jade and anorthite were collected and analyzed. Additionally, the distributions of Si, Al in the crystal structure were also discussed. UV-Vis spectra showed that dark green hue of this mineral is associated with d--d electronic transition of Fe3+ and Cr3+.

[Application of Raman spectrometer (785 nm) to jadeite test].

Jadeite is a greatly appreciated gemstone and often referred to as "the king of jade". Because of the advances in processing the treated jadeite is becoming more and more difficult for identification. NIR (785 nm) Raman spectrometer exhibits advantage of non-destruction, quickness, accurateness, and weak fluorescence interferences. This work reports such a research conducted using a NIR Raman spectrometer for a large number of jadeite samples. Based on the spectra collected and analysis there after performed, it is evident that the instrumentation and analysis methodology used have provided great information and assessment assistance in the application. It was found that the spectral response in the green area of a natural jadeite is much stronger in intensity than that in the white area. This is attributed to the key factor, the content of Cr3+ in the area. In contrast the spectral response in the green area of a treated jadeite is much weaker and additional Raman peaks start to show up on the high Raman shift side. This is the evidence of added fluorescence phenomenon and epoxyresin. It was also discovered that certain Raman features disappear compared to a natural sample. This indicates that the jadeite has been treated with acid and filled with colorless glue, which io turn destroyed the original exterior structure of a jadeite.