田黄颜色及萝卜纹研究

A study of color and Luobowen of Tianhuang stone

对中国寿山田黄石进行了薄片观察、扫描电子显微镜(SEM)观察及能谱(EDS)测试、显微拉曼光谱(Raman)测试、激光剥蚀等离子质谱(LA-ICP-MS)测试、全铁化学分析和电子顺磁共振(EPR)测试,以研究田黄的萝卜纹及颜色成因。放大及薄片观察显示,萝卜纹与基体无明显规则的界限,并呈体状扩散。SEM、EDS和拉曼光谱测试表明田黄萝卜纹的矿物成分为硫磷铝锶石,主要呈碎屑状集合体和纤柱状集合体,为原生特征。LA-ICP-MS和全铁化学分析表明三价铁离子导致田黄呈黄色,电子顺磁共振测试表明铁在田黄中主要以游离态的形式存在,认为是水田环境中铁(氢)氧化物吸附于组成田黄的层状硅酸盐矿物颗粒表面而呈黄色,为次生色。

The Tianhuang stone from Shoushan in China was studied by using slice observation, SEM, EDS, micro-Raman spectra, LA-ICP-MS, total iron analysis and EPR with the purpose of investigating the Luobowen and color genesis of Tianhuang stone. Under close magnification, no obvious regular boundary exists between matrix and Luobowen which diffuses around. SEM, EDS and micro-Raman spectral analysis show that svanbergite is the main mineral composition of the Luobowen. Svanbergite was formed before the formation of the matrix. Luobowen shows primary characteristics. LA-ICP-MS and total iron analysis indicate that Fe3＋ causes yellow color, and EPR studies show that iron exists in the Tianhuang stone in the free state. The authors hold that iron oxides and/or iron hydroxides are adsorbed at the surface of layered silicate mineral grains, leading to secondary color.