黄绿色松脂岩玉的宝石学特征

近期，笔者在检测中见到一批黄绿色玉石原石样品，外观呈油脂光泽、黄绿色，可见白色斑点，外形似软玉。为查明其成分，经客户同意后对样品进行切磨抛光。利用宝石显微镜、X射线粉末衍射仪、红外光谱仪等仪器进行了测试分析以及岩石薄片分析。宝石显微镜、X射线粉末衍射仪、红外光谱仪的结果分析，很容易将结果误判为长石质玉，岩石薄片分析表明该样品基质由火山玻璃组成，含微斜长石以及石英斑晶，属于花岗岩类的松脂岩，根据国标应定名为松脂岩玉。

Gemmological Characteristics of Yellow-green Pitchstone Jade

Recently the authors received some yellow-green jade samples, which were translu- cent 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 dif- fraction spectrometer（XRD）, Fourier transform infrared spectrometer （FTIR） and slice i- dentification. Infrared spectra of the samples are similar with those of microcline. XRD tes- ting 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--2010 jewelry 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.