热处理对黝帘石颜色的影响及其致色成因探讨——以坦桑尼亚黄色和蓝色黝帘石为例  

Study on the effect of heat treatment on the color of zoisite and the cause of coloration:The example of yellow and blue Tanzanian zoisite

作　　者：杨淑淇 刘迎新[1] YANG Shu-qi;LIU Ying-xin(School of Gemmology,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)珠宝学院,北京100083

出　　处：《岩石矿物学杂志》2024年第3期503-517,共15页Acta Petrologica et Mineralogica

摘　　要：坦桑尼亚的天然蓝紫色黝帘石(也被称为坦桑石)产量稀少,储量较低。然而,通过热处理优化改色后,黝帘石的经济价值会得到显著提升。但多年来,关于热处理后黝帘石的蓝紫色成因一直存在争议。本文选取天然的坦桑尼亚黄色及蓝色黝帘石为研究对象,通过设置300℃、400℃和500℃3个不同的温度条件,并利用L^(*)a^(*)b^(*)颜色参数对样品的颜色变化进行了量化分析。热处理前不同颜色黝帘石的宝石学特征具有一致性,热处理后结果表明,500℃左右的温度是浅蓝-蓝色黝帘石的最佳改色条件。经过热处理黝帘石的蓝紫色调明显增强,通过调整温度可有效调控样品中的黄色或褐色调。黄色黝帘石在热处理后展现出从黄褐色到蓝紫色的独特变色效应,而400~500℃是这一颜色变化的临界温度范围。结合EDXRF、LA-ICP-MS及UV-VIS等多种分析手段,认为天然黝帘石的蓝色主要由V^(3+)和Ti^(3+)导致,黄色则主要由Ti^(3+)引起,V/Ti值在天然黝帘石的成因机制中起辅助作用。此外,热处理后黝帘石蓝紫色调的产生与增加以及黄色→蓝-蓝紫色的转变与Ti^(3+)+V^(4+)→Ti^(4+)+V^(3+)的电荷迁移密切相关。The natural Tanzanian zoisite(tanzanite),with its distinctive blue-violet tone,is a rare and valuable gemstone.Heat treatment can optimise the color of zoisite and make it more economically valuable.However,the exact cause of this captivating blue-violet of zoisite has been a subject of debate for years.This study presents an examination of natural yellow and blue zoisites.The color changes of stones at different thermal stages were ob-served by setting three different temperature conditions 300℃,400℃and 500℃,and using the L^(*)a^(*)b^(*) color pa-rameter.The research findings indicate that the gemological properties of different colored zoisites remain consistent before heat treatment.It was determined that a temperature of approximately 500℃ is optimal for achieving a light blue-violet tone in zoisite.Heat treatment results in a pronounced enhancement of the blue-violet hues,enabling the modulation of zoisites'yellow or brown undertones through temperature control.Notably,the yellow zoisite expe-riences a fascinating color transformation from yellow-brown to blue-violet,with the critical temperature range between 400℃ and 500℃.Usingenergy dispersiveX-Ray spectroscopy(EDXRF),laser ablation inductively coupled plas-ma mass spectrometry(LA-ICP-MS)and ultraviolet and visible spectrophotometry(UV-VIS)techniques,the study identified that the blue color in natural zoisite is primarily caused by V^(3+)and Ti^(3+)ions working in tandem.On the other hand,the yellow color is mainly attributed to Ti^(3+).The V/Ti ratio plays a supporting role in coloration of nat-ural zoisite.Moreover,the development and intensification of blue-violet tones in heat-treated zoisite,as well as the transition from yellow to blue-violet,are intricately linked to the charge migration of Ti^(3+)+V^(4+)→Ti^(4+)+V^(3+).

关 键 词：坦桑尼亚黝帘石 热处理 颜色 致色成因 

分 类 号：P578.94[天文地球—矿物学]