浅析出土软玉质玉器的沁对玉质鉴定的影响

Influence of Soaking of Unearthed Tremolite Jade Artifact on Jade Composition Identification

沁色不仅是出土玉器的常见重要特征,而且被认为是有价值的"美",所以,仿古玉器一般都会仿制沁色。出土玉器受沁作用和沁色会影响玉器玉质的宝石学特征,从而会影响对玉器玉质的正确鉴定。本文以4处软玉质出土玉器特征的研究成果为基础,根据出土玉器受沁特征的研究分析,初步探索了受沁作用和沁色对玉器颜色、光泽、透明度、孔隙度、密度、硬度等宝石学特征的影响和受沁后玉石成分的变化规律,以期为出土玉器的正确鉴定和仿古玉器伪沁的辨析提供参考和帮助。研究结果表明:(1)受沁对出土玉器颜色的影响规律是,受沁程度不同则影响表观颜色的程度不同,玉器受沁程度越严重,对玉器表观颜色的改变越大,一般是颜色变深;(2)受沁对出土玉器光泽和透明度的影响规律是,受沁越严重则玉器的光泽和透明度越差,从未受沁—轻度—中度—较重—重度受沁,光泽的变化一般呈现玻璃光泽—亚玻璃光泽—油脂光泽—蜡状光泽—土状光泽的变化,透明度的变化一般呈现透明—亚透明—半透明—不透明的变化;(3)受沁对出土玉器的密度、孔隙度和硬度的影响规律是,受沁越重孔隙度增大,相应地密度和硬度降低,如严重受沁的透闪石质玉器,其摩氏硬度一般小于5.5,最低可到4,最高可到6;(4)受沁对出土玉器成分的影响规律是,主要矿物组成一般不变化,玉石种类也不变化,只是有的玉器局部可产生化学元素种类和含量的变化。

Soak-induced colour is not only an important apparent feature of unearthed jade artifacts,but also considered to be a valuable＂beauty＂.So usually,imitated soak-induced colour has been seen in imitated ancient jade artifacts.The soak-induced colour can influence the gemmological characteristics of the jade and identification of jade composition.Based on the research conducted on unearthed jade artifacts from four different archeological sites,this paper presents a results of the influence of soaking on ancient jade artifacts,especially onluster,colour,transparency,porosity,density,hardness,composition etc.Such that useful information on how to identify the components of ancient jade accurately and how to discriminate fake soak-induced colour on imitated jade artifacts can be elucidated.In conclusion,Soaking influences the colour of unearthed jade.The more serious damage is caused by soaking,the more colour change is visible-usually darker.Soaking influences luster and transparency.The more serious damage is caused by soaking,the worse the luster and transparency become.With the degree of soaking change from mild to severe,luster changes generally from glassy luster to sub-glass luster then to greasy luster,wax luster and finally soil luster.Changes in the general transparency is from transparent to sub-transparent to translucent,and finally opaque.Soaking influences the density,porosity and hardness of the unearthed jade accordance.The more serious damage is caused by soaking,the higher the porosity is,thus it reduces the density and hardness.For example,the hardness of seriously soaked tremolite jade may become less than 5.5（ranging from 4up to 6）.Soaking also influences jade composition.The main mineral components generally do not change and jade species does not change as well,but some parts may change in the type and concentrations of chemical elements.