碧石的宝石学分类及定义界定初探

PRELIMINARY STUDY ON DEFINITION AND GEMOLOGICAL CLASSIFICATION OF JASPER

碧石属于石英质玉中一类,少有文献对其深入探讨,缺乏系统性分类以及定义界定,不能准确区别于颜色相对应的玉髓(玛瑙)。为解决上述问题,本次研究应用X射线衍射、拉曼光谱、红外光谱、电子探针、紫外-可见光光谱等多种测试技术相结合方式,初步确定常见单色碧石的致色矿物,其中红碧石的致色矿物为赤铁矿,黄碧石的致色矿物为针铁矿,绿碧石的致色矿物为绿鳞石,紫碧石的致色矿物是锐钛矿和赤铁矿。结合市场实际需求,从宝石学角度以颜色特征作为碧石分类依据,将碧石从宝石学分类角度,分为红碧石、黄碧石、绿碧石、紫碧石、血滴石、风景碧石、多彩碧石等七个大类。同时,根据X射线衍射半定量分析和电子探针测试近似计算结果:红碧石测试样品中赤铁矿平均含量均不低于2.187%,凉山南红样品红色富集区域测试赤铁矿含量不高于1.767%,低于2%。因此可以考虑将2%的赤铁矿含量作为区别红碧石和南红的界限。建议以杂质矿物含量2%对碧石和相似颜色的玉髓(玛瑙)区分界定,进一步补充完善已有碧石定义。

Jasper belonging to a class of quartz jade is rarely discussed in depth in the literature,which lacks systematic classification and definition,and can not be accurately distinguished from chalcedony(agate)according to the color.In this paper,X-ray diffraction,Raman spectroscopy,infrared spectroscopy,electron probe,UV-visible spectrum and other testing techniques have been used to determine the chroma-ticity minerals of common monochromatic quartz.The results reveal that different jasper is colorized by different mineral inclusions.Among them,red jasper is colorized by hematite,yellow jasper is colorized by goethite,green jasper is colorized by chlorite and purple jasper is colorized by anatase and hematite.Based on the gemological principle and in consideration of the market demand,jasper can be divided into seven categories,including red jasper,yellow jasper,green jasper,purple jasper,blood drop jasper,landscape jasper and colorful jasper.Meanwhile,the calculation and analysis of X-ray diffraction and Electron Microprobe testing data show that the hematite content of red jasper ranges from 2.187% to 2.5%and the content of Nanhong is about 1.767%.It is proposed that the total hematite content is important when it reaches to 2%,which can be used as a dividing line between jasper and chalcedony(agate).It is suggested that the impurity mineral content of 2% should be used to distinguish and define jade stone and chalcedony(agate)of similar color,so as to further supplement and perfect the existing definition of jade stone.