三种绿色印章石的宝石矿物学特征

近两年,我国珠宝市场上出现了大量的＂西安绿＂＂丹东绿＂等绿色印材,其多被用来仿冒绿色寿山石（＂月尾绿＂）,并以高价售卖。采用X射线粉末衍射仪,电感耦合等离子质谱仪,扫描电子显微镜等测试仪器,对＂西安绿＂＂丹东绿＂的矿物组成、化学成分以及微观结构进行分析,并与寿山＂月尾绿＂的宝石矿物学特征进行了对比。结果表明,＂月尾绿＂主要由铬云母组成,Cr,Fe元素是其呈浅绿色并略带灰黄色调的主要原因之一;＂西安绿＂主要由伊利石组成,其Cr,V元素的质量分数远高于＂月尾绿＂中的,且前者几乎不含Fe元素,这可能是其呈艳丽绿色的主要原因;＂丹东绿＂主要由斜绿泥石组成,Fe元素的质量分数较高且几乎不含Cr元素,致使其呈现较深的暗绿色。扫描电子显微镜的观察结果发现,与＂月尾绿＂相比,＂西安绿＂中伊利石的片晶厚、粒度小,＂丹东绿＂中斜绿泥石的片晶薄、堆积紧密,挠性发育。这三种绿色印章石在绿色色调、光泽、密度、内含物等方面存在不少的差异,可作为其鉴别特征。

Gemmological and Mineralogical Characteristics of Three Green Seal Stones

＂Xi＇anlv＂ and ＂Dandonglv＂ are used as the imitations of green larderite（＂Yueweilv＂） in the jewelry market recently.Mineral components,chemical compositions and microstructures of ＂Xi＇anlv＂ and ＂Dandonglv＂ are investigated by using the XRD,ICP-MS and SEM,which are also compared with ＂Yueweilv＂.The results show that ＂Yueweilv＂ is mainly composed of fuchsite,where the Cr and Fe elements lead to a slightly gray-green tone in colour;that ＂Xi＇anlv＂ is mainly composed of illite with much lower Fe,and the content of elements Cr and V are much higher than those of ＂Yueweilv＂,which may be the main reason for the green colour of ＂Xi＇anlv＂;and that ＂Dandonglv＂ is mainly composed of clinochlore with higher Fe and lack of Cr elements,which is the main reason for its dark-green tone in colour.The observation by SEM shows that the lamellar crystal of illite is small but thick in ＂Xi＇anlv＂ and that the lamellar crystal of clinochlore is thin,flexible and piled up closely in ＂Dandonglv＂.The three kinds of green seal stones mentioned here are quite different in colour,luster,weighting,and inclusion,due to their different compositions and microstructures.