Distilling zinc with zinc sulfide ores: The technology of Qing Dynasty zinc production in Guiyang, Central South China

Abstract It is difficult to distill metal zinc partly due to the reduction temperature of zinc oxide ores close to the boiling point of metallic zinc. The treatment of zinc sulfide ores is more complicated since they have to be roasted before smelting. Previous archaeometallurgical studies on zinc smelting technology in China mainly focus on the distillation of zinc oxide ores. This paper, for the first time, presents analytical results of archaeological evidence about the distillation of zinc sulfide ores in Guiyang in southern China dated back to the Qing Dynasty (CE 1636–1912). The smelting remains including ores, distillation retorts and slags, especially the roasting hearths and zinc calcine firstly discovered and confirmed in zinc smelting sites were characterized comprehensively by p-XRF, OM, SEM-EDS and XRD. It was revealed that the zinc smelting technology in the Tongmuling site and the Doulingxia site was mainly based on the distillation of zinc sulfide ores, which should be oxidized by a lengthy roasting processing at the lower temperature before the distilling. In order to enhance the condensation efficiency, the height of the condensers in the distillation retorts has been significantly increased. Most of the zinc products were ordered by the Minting sub-Bureau of Baonan in Changsha.