Gemmological Characteristics of Yellow-green Pitchstone Jade

Recently the authors received some yellow-green jade samples, which were translucent and opaque rough stones with glass-to-greasy luster and have some white spots.The yellow-green jades were studied by using the gemmological microscope, X-ray powder diffraction spectrometer (XRD), Fourier transform infrared spectrometer (FTIR) and slice identification.Infrared spectra of the samples are similar with those of microcline.XRD testing results indicate that the samples contain microcline and quartz, according to the results of infrared spectra.However, according to analyses of thin rock slice, the sample presents porphyritic texture, with about 20% feldspar and quartz and about 80% glass matrix.The white spots are microcline and quartz in sample.According to GB/T 16552-2010jewelry name, the samples can be called pitchstone jade.By using conventional gemmological testing methods, IR and XRD, it is easy to confuse the samples with feldspar jade.The reason is that infrared spectra of feldspar and volcano glass are similar and prone to overlap, and XRD could not detect amorphous substance, which as a result only shows the main characteristic peaks of feldspar.Using slice observation analysis, the main matrix of the samples is volcano glass with microcline and quartz. This kind of mineral is easily mistaken in appearance as well as data analysis, and more attention should be paid in the daily examination.