Germanium: Germanium Dioxide Reduced with Carbon at Full Red Heat, Fused under Borax (Roscoe 1913)

Carbon takes the oxygen from germanium dioxide at a full red heat. Washing removes the leftover carbon and a little borax melts the regulus clean. Result: greyish-white, brittle, lustrous germanium (sp. gr. 5.47, melts about 960 °C), often in octahedra. Source: Roscoe and Schorlemmer, A Treatise on Chemistry vol. 2 (1913), p. 838. Not given: amounts and vessel. Picture drawn by Youblob.