绿松石呈色机理初探

Elementary research on color-forming mechanism of turquoise

矿物的成分、结构和键型是复杂的,所以引起矿物颜色变化的因素也是复杂的:一种矿物的颜色往往是多种呈色机制的总效应。绿松石是一种自色玉石,即它的颜色是由自身的成分和结构决定的。电子探针分析了不同颜色的绿松石的化学成分,从实验结果看出,绿松石的颜色主要由Cu2+、Fe3+离子决定,Cu2+离子对绿松石的基色——天蓝色起有益作用,而Fe3+起相反作用,二者含量多少决定了色调的变化特点。这与用晶体场理论和光谱实验观测解释的呈色机制是一致的。差热分析和热分析结果认为,吸附水和结晶水的存在对绿松石的颜色有一定影响:吸附水含量较高的样品,其颜色较深;当样品经300oC灼烧后(绿松石失去部分或全部结晶水),其颜色发生明显变化,由蓝变为黄绿。

On account of the complexities of mineralogical composition,structure and bond,the factors of leading to the variation of color are complicate.The color of a mineral is often the effect of many factors.Turquoise is a kind of jade that shows its own color,that is to say,the color of turquoise is determined by its own components and structures.Through microprobe analysis,the turquoise′s components of distinct color are studied,and the result shows that turquoise′s color is decided by Cu^(2+) ions and Fe^(3+)ions,the basic color of turquoise is related to the existence of Cu^(2+) octahedron,which is beneficial effect,but Fe^(3+)ions lead to the reverse.The crystal field and the spectrum experiment analysis get the coincident conclusion.The differential thermal analysis(DTA) and thermal analysis get the conclusion that some effects on the color of turquoise are come into being because of absorped water and crystalline water:the more the absorped water contains,the deeper the color is.When it is heated to 300(~oC)(turquoise loses a part of or the whole crystalline),turquoise′s color is changed obviously from blue to green.