Gemmological Characteristic of Petrified Wood from Qitai, Xinjiang and Pagan, Burma

Conventional gemmological methods, polarizing microscope, scanning electron microscope(SEM), electron microprobe analysis(EMPA), X-ray powder diffraction(XRD) were carried out to obtain the microstructures, gemmological and mineralogical characteristics of petrified wood samples from Pagan, Burma and Qitai, Xinjiang, China. The result shows that the petrified wood samples from two regions consist of quartz (account for over 90% SiO₂), which is microcrystal to nanocrystal, and other minor minerals (such as pyrite, dolomite, clay mineral). Through calculating the crystalline index of quartz, together with observing the quartz morphology under scanning electron microscope, the quartz in petrified wood from Pagan, Burma, shows significantly higher crystallinity than that from Qitai, Xinjiang, China. In addition, in the petrified wood from Qitai, Xinjiang, the semitransparent part is fine radial quartz particles or fibrous chalcedony, but the slightly transparent part is granular quartz particles which are not compact. The wholly opaque petrified wood from Burma is granular quartz whose size is at the micron level.