墨绿色钠长石玉的初步研究

以墨绿色钠长石玉样品为研究对象,采用常规的宝石学测试、偏光显微镜、电子探针、X射线粉末衍射等分析方法,从宝石学特征、矿物组成、结构特征、有序度等方面,对该钠长石玉进行了较全面的研究。结果表明,墨绿色钠长石玉的折射率为1.53（点测）,密度约为2.64g/cm^3;其薄片中矿物晶体的形态主要呈半自形-他形粒状、短柱状和纤维状,结构主要有糜棱结构和纤维粒状变晶结构,主要矿物组成为钠长石和角闪石。电子探针的化学成分分析显示,样品中钠长石的An值小于0.006,说明钠长石的成分很纯;所含的角闪石种类主要为镁钠铁闪石。由X射线粉末衍射峰数据计算出钠长石的结构有序度极接近于1,其为完全有序的低钠长石,形成温度低于300℃。本文填补了钠长石玉研究中的一些空缺,为钠长石玉的系统性和综合性研究提供一些有意义的理论成果。

Preliminary Study on Dark-green Albite Jade

The gemmological characteristics,mineral components,texture feature and degree of order of the dark-green albite jade are systematically studied by using many kinds of analytical methods,such as conventional gemmological methods,polarizing microscope,electron microprobe and X-ray powder diffraction.The results show that the refractive index of the dark-green albite jade is about 1.53 with density of 2.64 g/cm3.In the petrographic thin sections,the mineral crystals are mainly hypidiomorphic to xenomorphic granular,short prismatic and fibrous.There are two major kinds of texure,mylonitic texture and fibrous granular crystalloblastic texture.The main mineral components are albite and amphibole.The results of chemical compositions of samples by using electron microprobe are that the values of An of albite is less than 0.006,which suggests that the albite ingredient is very pure.The major amphibole type is magnesioarfvedsonite.Based on the X-ray powder diffraction data,the degree of order of albite structure has been calculated,which is very close to 1.It is completely ordered low albite.The formation temperature is lower than 300℃.The present paper makes up some deficiencies in the research on albite jade and provides some meaningful theoretical achievements for the further systematic and comprehensive research on it.