陕西商洛紫绿玛瑙的宝石学特征及致色机理研究

通过常规宝石学仪器、偏光显微镜、电子探针及扫描电子显微镜等检测手段,对陕西商洛紫绿玛瑙的宝石学特征及致色机理进行了深入研究。研究表明,紫绿玛瑙是典型的石英质玉石,颜色以绿色、紫红色为主,颜色分布多以紫心绿边、灰白心绿边、淡青白色加紫红色等纹带特征出现,半透明—微透明,部分透明度较好的区域可见明显包裹体。紫绿玛瑙为典型的隐晶质结构,主要组成矿物为石英,结晶程度较好,为呈半自形—他形结构,含量≥90%,粒径为1~25μm,分布均匀;次要矿物有绿泥石、绢云母、铁白云石、白云石等。紫绿玛瑙为矿物致色,紫红色的致色矿物为铁的氧化物或氢氧化物,粒度微细,粒径为1~10μm,呈星点状均匀分布,含量为1%~2%;绿色的致色矿物为绿泥石,含量较高(6%~7%),主要呈集合体状均匀的分布于石英粒间,绿泥石含量与绿色区域的颜色深浅程度成正比。

The gemological characteristics and color mechanism of purple green agate in Shangluo,Shaanxi

The gemmological characteristics and color mechanism of the purple green agate in Shangluo,Shaanxi Province are analyzed by conventional gemmological instruments,polarized microscope,electronic probe and scanning electron microscope.Research result shows that the purple green agate is a typical quartz jade.The main colors are green and purple,and the characteristics of color texture are obvious with purple-heart-green-edge,gray-white-heart-green-edge,light cyan-white and purple-red belt,and so on.The transparency is translucency-semitransparency,some areas are more transparent and the inclusion can be seen clearly.Purple Green Agate is a typical cryptocrystalline structure,and its main mineral is quartz which is evenly distributed with a content of more than 90%.Its crystallinity is generally in the form of a semi-self-other structure,the size is about 1-25μm.The secondary minerals are chlorite,sericite,iron dolomite,dolomite and so on.Minerals are the origin of the color of the purple green agate.The chromophoric mineral of purple color is iron oxide or hydroxide with a content about 1%-2%,of fine particle size about 1-10μm and the star-like uniform distribution.In the green part,chlorite is the most important color mineral,with a high content of 6%-7%.It is mainly distributed among quartz grains in an aggregate shape,and the content of chlorite is directly proportional to the color depth of green areas.