Warning: Missing argument 3 for write(), called in /www/wwwroot/biwei1.cn/incs/robot.php on line 68 and defined in /www/wwwroot/biwei1.cn/incs/data.php on line 487 Rainbow crystal geodes let you hold a dazzling combination of colors in your hand. But to achieve this brilliant effect, humans have to intervene with a process called metal coating [source, read more: ]