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

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, 0.25189, 0.24510, 0.21806, 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.