Formation Mechanism and Gemological Characteristics of "Yellow-Skinned" Nanhong Agate in Northeastern Yunnan, China: Evidence from Mineralogy and Geochemistry. - Song, Qiuyun; Zhang, Shitao; Pu, Wenzhou; Chen, Liurunxuan; Zuo, Ruohan; Chen, Xianchao; Zhang, Dai; Liu, Wenlian (Crystals (2073-4352), 2025)