What happens next is known as the Siemens process and it involves breaking down that pure silicon metal into its elemental pieces and re-forming them all over again. The metal is ground into a powder, mixed with pure hydrogen chloride, distilled and then heated up in a bell jar to 1,150°C. At the end you are left with long rods a little like the heating elements in an old kettle, except that the material here is not furred-up limescale but ultra-pure silicon.
