五种常见中低档绿色宝石致色机理研究

Study on Color Genesis of Five Common Middle and Low Grade Green Gemstones

绿色宝石因其美丽的颜色深受人们喜爱,但高品质的高档绿色宝石较为稀少,而品质稍差的中低档绿色宝石产量较高,种类繁多。近年来,随着物质生活水平的提高,人们对中低档宝石的关注逐渐增加,但许多宝石因颜色不够好而使其价值受到了很大的影响。如果能对中低档宝石适当改色,改善其品质,便可以从中获得巨大的经济利益和显著的社会效益。而宝石改色的重要前提是要了解其呈色机理。本文选取蛋白石、葡萄石、萤石、磷灰石、碧玺五种常见中低档宝石的绿色品种作为研究对象,通过紫外–可见光光谱和X射线荧光光谱,探究其呈色机理。研究表明绿色宝石的致色离子主要是Cr3+、Fe2+、Fe3+、V3+、Ni2+和一些稀土元素,本文研究的绿色宝石样品的呈色机理主要有三种,1) 电子跃迁致色:蛋白石为Ni2+的电子跃迁致色;碧玺为Mn3+和Fe2+的电子跃迁致色;葡萄石为Fe2+电子跃迁致色;萤石为Cu2+的电子跃迁致色。2) 电荷转移致色:碧玺为Fe2+和Fe3+的电荷转移致色。3) 色心致色:磷灰石为F−-V−F-F−的电子色心致色;萤石为稀土元素引起的色心致色。此外,宝石的颜色通常是由多种呈色机理共同决定的混合色。通过研究,初步探讨了几种绿色宝石的呈色机理,为绿色宝石的呈色机理提供了理论参考。

Green gemstones are popular because of their beautiful color, but high-quality high-grade green gemstones are rare, while lower and middle-grade green gemstones of a slightly lower quality are produced in high quantity and are of various kinds. In recent years, with the improvement of the material living standard, people pay more and more attention to the middle and low-grade gems. However, the value of many gems is greatly affected because the color is not good enough. If we can properly change the color of middle and low-grade gems and improve their quality, we can obtain huge economic benefits and significant social benefits. The important premise of gem color change is to understand its color mechanism. In this paper, five green varieties of common middle and low-grade gemstones, opal, grape, fluorite, apatite and tourmaline, were selected as the research objects, and their color mechanism was explored through UV-visible light spectrum and X-ray fluorescence spectrum. Studies have shown that the main chromogenic ions of green gemstones are Cr3+, Fe2+, Fe3+, V3+, Ni2+ and some rare earth elements. There are three main chromogenic mechanisms of green gemstones studied in this paper: 1) Electron transition: Opal is Ni2+ electron transition chromophoresis;Tourmaline is the electron transition chromaticity of Mn3+ and Fe2+;The grape stone is colored by Fe2+ electron transition. The color formation of fluorite may be caused by Cu2+ electron transition. 2) Charge transfer color: Tourmaline is the charge transfer chromaticity of Fe2+ and Fe3+. 3) Color-centric color: Apatite is F−-V−F-F− electronic color center;Chromophores are caused by fluorite rare earth elements. In addition, the color of gemstones is usually a mixture of colors determined by a variety of color mechanisms. The color mechanism of several green gemstones is preliminarily discussed, which provides a theoretical reference for the color mechanism of green gemstones.