Process for preparing highly purified silicon and optionally aluminum and silumin (aluminum silicon alloy) in the same cell, wherein silicate and/or quartz containing rocks are subjected to electrolysis in a salt melt containing fluoride, whereby silicon and aluminum are formed in the same bath, and aluminum formed, which may be low alloyed, flow to the bottom and is optionally drawn off, and deposit formed on the cathode is removed from the cathode and crushed, optionally together with the remaining electrolysis bath, concentrated sulfuric acid and then hydrochloric acid and water are added to the crushed material, liberated Si-grains float to the surface and are taken out and treated further as desired.