石榴石的品种及鉴定

Variety and Identification of Garnet

  • 摘要: 本文通过对比不同品种石榴石的常规宝石学特征和红外光谱特征,以期找到一种可以快速区别不同品种石榴石的方法。结果表明,铝系列和钙系列石榴石之间的区别较为简单:铝系列一般为暖色系的红色、橙色等,而钙系列一般为冷色系列的绿色;铝系列石榴石B带频率一般高于870cm-1,且常缺少D带,而钙系列石榴石B带频率一般低于870cm-1,而且一般具有D带。钙系列中钙铝榴石、钙铁榴石由于完全类质同相混溶较少,通过折射率和红外光谱也可以较好区别:钙铝榴石折射率一般小于1.78,钙铁榴石折射率一般大于1.78;钙铝榴石的红外光谱B带一般在864cm-1左右,而钙铁榴石的B带一般在837cm-1左右。铝系列中镁铝榴石、铁铝榴石、锰铝石榴石由于相互混溶现象普遍,需要综合颜色、折射率和红外光谱特征才能进行准确的判定。

     

    Abstract: In this paper,the common characteristics and infrared spectra of different varieties of garnets are compared in order to find a fast way to distinguish garnet.The results show it is relatively straightforward to separate pyralspite series from ugrandite series.The colour of pyralspite series usually shows warm-toned,such as red and orange,on the other hand urgrandite series often shows cool-toned such as green colour.The B-zone frequency of pyralspite infrared spectrum is higher than 870cm-1 and there is usually no D-zone frequency.The B-zone frequency of ugrandite is lower than 870cm-1 and it shows D-zone frequency in the infrared spectrum.Because grossular and andradite are incomplete isomorphism series,it is also relatively straightforward to separate grossular from andradite.The refractive index of grossular is lower than 1.78and the B-zone infrared frequency of grossular is at 864cm-1.While the refractive index of andradite is higher than 1.78and the B-zone infrared frequency of andradite is at 837cm-1.Because the pyrope,almandine and spessartine are isomorphism series,it is difficult to separate them.The colour,refractive index and infrared spectrum should be considered overall to make a accurate conclusion.

     

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