近年来宝石扩散处理的改色研究进展

The Research Development of Colour Change of Gemstones by Diffusion Treatment in Recent Years

宝石的扩散改色是一种处理工艺,主要机理是在热处理过程中添加特定的致色剂或活化剂,辅以温度、恒温时间和氧化还原环境的控制,从而达到部分或整体改变宝石颜色的目的。扩散改色按照着色层的深度可分为表面扩散和体扩散处理。目前比较常见的扩散处理方法包括:Ti元素的表面扩散处理,Co元素的表面扩散处理,Cu元素的表面扩散处理,Bc元素的体扩散处理以及Mg元素的体扩散处理。根据前人研究,Ti^(4+)与Fc^(2+)联合扩散无色-浅色蓝宝石可得到深蓝色蓝宝石,还能产生星光效应;Co元素可以使浅色托帕石和尖晶石变为深蓝色;对无色至黄色长石进行Cu的扩散处理可以得到红色长石;Bc扩散则可以使过深的蓝宝石色调减弱,与其他致色元素联合后更可以得到颜色多样的扩散蓝宝石,但由于其剧毒的特性,操作时需要非常严格的工作环境,近来有研究者提出一种Mg代替Bc的体扩散处理工艺,并成功将浅色蓝宝石改变为黄色。

Colour change of gemstones by diffusion treatment is a type of treatment process. Its main mechanism is to add a specific colouring agent or activator in the process of heat treatment, and assisted by the control of temperature, holding time and redox environment, so as to partially or entirely change the color of the gemstones. Diffusion modification can be divided into surface diffusion and bulk diffusion according to the depth of color layer. The common methods of diffusion treatment at present include： surface diffusion treatment of Ti element, surface diffusion treatment of Co element, surface diffusion treatment of Cu element, bulk diffusion treatment of Be element and bulk diffusion treatment of Mg element. According to previous studies, indigo sapphire with asterism can be abtained through combined diffusion of colourless-light colour sapphire by Ti4＋and Fe2; Co element can change the color of light colour Topaz and spinel into deep blue;red feldspar can be obtained through Cu diffusion treatment of colorless to yellow feldspar;Be diffusion can weaken the hue of the deep colored sapphire, when combined with other colored elements, diffused sapphire of different colors can be obtained. However,due to its hypertoxic nature, a very strict working environment has to be met during the operation. Recently, a bulk diffusion process to substitute Be by Mg has been proposed by researchers and the light colour sapphire has been successfully changed into yellow color by this technique.