“云南绿松石”的鉴定、颜色成因与宝石学特征研究

The Identification,Color Genesis and Gemmological Characteristics of"Yunnan turquoise"

近期,云南珠宝市场盛行一种新型“绿松石”品种,商家称作“云南绿松石”,上品全绿,以大而美著称。现有资料表明云南省仅安宁对门山区域曾有绿松石出产,但该矿点已被列为保护矿区禁止开采。本文通过常规宝石学测试、红外光谱、拉曼光谱、X射线粉晶衍射、X射线荧光光谱、激光诱导击穿光谱和电子探针等研究方法,对“云南绿松石”进行了样品鉴定和颜色成因分析。结果表明,“云南绿松石”实际为磷铝石质矿物集合体,在宝石学基本性质和谱学特征上与绿松石具有较大差异,抛光后呈现弱玻璃至玻璃光泽,表现为由浅至深的绿色,色泽浓郁,部分间杂白色、褐色条带;折射率为1.56~1.57;密度为2.52~2.56,紫外荧光均呈惰性;该产地磷铝石以“富铁贫铬”为致色元素特征,XRF和电子探针测试显示出Fe_(2)O_(3)和Cr_(2)O_(3)富集现象,紫外光谱显示出360 nm,640 nm吸收峰和690 nm吸收带,匹配为Fe^(3+)和Cr^(3+)的共同作用。

Recently,a new type of turquoise has gained popularity in the Yunnan jewelry market.It is called"Yunnan Turquoise"by the traders,and is famous for its vivid green color.Available data indicated that previously,Yunnan turquoise was sourced from the Duimenshan area of Anning,Yunnan Province.However,this mine has been designated as a protected mining zone and is now off-limits for excavation.In this study,we analyzed the composition and color origin of the"Yunnan turquoise"via conventional gemmological test,Fourier transform infrared(FIFR)spectroscopy,Raman microprobe spectroscopy,X-ray diffraction(XRD),X-ray fluorescence(XRF)spectroscopy,laser-induced breakdown spectroscopy(LIBS),and electron probe X-ray micro-analyzer(EPMA).Its fundamental gemmological properties and spectral characteristics are distinct from traditional turquoise.It appears a subtle glassy luster and dark to light green color.Some samples are with interspersed white and brown bands.Its refractive index ranges of 1.56 to 1.57,and its density varies from 2.52 to 2.56.Notably,it does not fluoresce under ultraviolet light.The colouring element characteristics in this region's variscite are rich in ferrum and poor in chromium.Both XRF and EPMA confirm the enrichment of Fe_(2)O_(3) and Cr_(2)O_(3).There absorption peaks at 360,640 and 690 nm in the ultraviolet spectrum are related to the combined effects of Fe^(3+)and Cr^(3+).