People visit the Hongshilin carbonatite cluster in Guzhang County, Xiangxi Tujia-Miao Autonomous Prefecture, central China's Hunan Province, June 28, 2015. The Hongshilin carbonatite cluster in Guzhang, the only red carbonatite cluster formed in the Cambrian Period in the world, has a history of about 450 million years. (Xinhua/Peng Biao)
