危地马拉与缅甸含绿辉石翡翠的矿物学对比研究

Mineralogical comparison between omphacite-bearing jadeite from Guatemala and that from Myanmar

以危地马拉蓝水料与缅甸油青种翡翠为研究对象,通过显微镜观察、岩石薄片观察、X射线粉末衍射分析、激光拉曼光谱分析、扫描电镜分析、电子探针分析等测试手段对两者进行了常规宝石学特征、结构特征、杂质矿物、化学成分等方面的对比研究。结果表明,危地马拉蓝水料发育等粒变晶结构,主要成分为硬玉,含有绿辉石,硬玉环带以2~3层为主,绿辉石分别以自形颗粒、交代残余、沿微裂隙充填3种形式存在,其中白色点状物为钠长石,绿色点状物为霓辉石和绿辉石的混杂物;缅甸油青种翡翠以硬玉为主颗粒相对粗大,呈柱粒状镶嵌结构,硬玉发育3~5层环带结构,绿辉石以脉状充填硬玉颗粒间隙或被硬玉颗粒交代呈孤岛状。危地马拉蓝水料硬玉颗粒与脉状绿辉石的CaO含量均高于缅甸油青种翡翠,另外由于霓辉石的存在,推测两产地翡翠结晶环境中的Ca、Fe含量可能存在差异。

Guatemalan"blue water"jadeite and Myanmar"oil green"jadeite were analyzed by means of microscope observation,thin section observation,X-ray powder diffraction,laser Raman spectrum,and scanning electron microscope analysis.The authors tried to compare these two jadeites in conventional gemological characteristics,structural characteristics,impurity minerals and chemical composition.The results show that the jadeite grains of Guatemalan"blue water"material develop homoeoblastic structure,and the major mineral is jadeite,with a small amount of omphacite,the jadeite particles show the rhythmic zoning with 2~3 layers,and the omphacite occurs as euhedral grains,residues of metasomatism or filling material along the micro-crack,in which the white punctate mineral is albite,and the green punctate mineral is a mixture of aegirine-augite and omphacite.The jadeites in Myanmar"oil green"jadeite have coarse particles and a columnar granular mosaic structure,with relatively uniform sizes.The mineral has pure jadeite and mottled omphacite as impurity mineral,the jadeite particles of Myanmar"oil green"jadeite show the rhythmic zoning with 3~5 layers,and the omphacite grains fills the gap of jadeite particles in vein shape or is replaced by jadeite crystals in island shape.Meanwhile,the content of CaO in Guatemala"blue water"and vein omphacite are higher than that in Myanmar"oil green"jadeite.In addition,with the existence of aegirine-augite,it is inferred that there may be differences in Ca and Fe content in the crystal environment of jadeite from the two producing areas.