应用同步辐射技术解析黄色-红色石英质玉石中的致色矿物

Investigation of Color Causing Minerals in Yellow-Red Colored Quartzite Jade Using the Synchrotron Radiation Technique

质地细腻、颜色多彩的隐晶质-微粒脉石英在我国珠宝行业称为石英质玉石,颜色是石英质玉石价值判断的主要因素之一,揭示其致色矿物及致色机理对于研究石英质玉石的颜色评价指标和矿床成因具有重要意义,但前人并未直接获得致色矿物的准确信息。本文运用上海光源(SSRF)BL15U1线站的同步辐射硬X射线,使用μ-XRF和μ-XRD技术对黄色和红色隐晶质-微粒脉石英中的致色矿物进行了研究。结果表明,黄色石英质玉石由赋存于石英颗粒间或微裂纹中的针铁矿(特征衍射峰0.49574、0.41594、0.26887、0.25705、0.25189、0.24510、0.21806、0.17133 nm)或其集合体致色,红色石英质玉石由赋存于石英颗粒间或微裂纹中的赤铁矿(特征衍射峰0.36774、0.27091、0.25200 nm)或其集合体致色,黄色-红色石英质玉的颜色由针铁矿和赤铁矿共同致色,赤铁矿的显色能力要高于针铁矿。本文获得了石英质玉石中致色矿物的直接数据,为玉石结晶温度与致色机理的探讨、石英质玉石的品质评价提供了依据。

Jade-like cryptocrystalline-microcrystalline vein quartzite is called quartzite jade in the jewel business of China. Color is the main criteria for the value of quartzite jade,and therefore studying the coloration mechanism is very important for the color evaluation index and ore genesis. Previous studies have shown that the accurate information of color causing minerals cannot be acquired. The synchrotron radiation techniques,BL15U1 in SSRF equipped with μ-XRF and μ-XRD at SSRF were used for studying the color causing minerals in vein quartzite and are reported in this paper. It was found that yellow vein quartzite is colored by goethite （characteristic diffraction peaks at 0. 49574 , 0. 41594 ,0.26887,0.25705,0 .2 5 1 8 9,0 .2 4 5 1 0,0 .2 1 8 0 6,0.17133 nm ） ,whereas red quartzite is colored by hematite （characteristic diffraction peaks at 0. 36774 , 0.27091, 0. 25200 nm）. Yellow-red quartzite is colored by both goethite and hematite and hematite has a stronger coloration ability than goethite. This study provides direct data of the color causing minerals in quartzite jade , which is useful for discussing the crystallization conditions and the coloration mechanism, and also helpful for the quality evaluation of quartzite jade.