Experts investigate at an ancient smelting site in Guiyang county in Central China's Hunan province on November 8, 2016. Archaeologists have unearthed evidences such as smelting furnace and slag on the ruins dating back to the late Ming Dynasty (1368-1644). The discovery of the site, as well as the findings of smelting ruins have provided new material for the study of ancient zinc smelting techniques in China. [Photo/VCG]