Why does Zhangpu shrimp red stone turn yellow?

Long-term storage or transmission. The surface of iron, carbon dioxide and water vapor stored or transported in the air for a long time is easy to turn yellow. Zhangpu County is located in the south of Minnan Golden Triangle, bordering Taiwan Province Strait in the east, Dongshan and Shantou in the south and Zhangzhou and Xiamen in the north. Located at the southern end of the southeast coast of Fujian.