《天工开物·下篇·五金》
日本等处的铜矿，也有与银矿在一块的，当放进炉里去熔炼时，银会浮在上层，而铜沉在下面。
东夷铜又有托体银矿内者，入炉炼时，银结于面，铜沉于下。
Copper mines in Japan and other places also had silver mines together. When they were put into the furnace for smelting, the silver would float on the upper layer, and the copper would sink to the bottom.