Complex sentence: The gold precipitate is then filtered out of the solution, mixed with fluxes and smelted to form crude and impure bars which are sent to a refinery to remove the copper and silver, the process used depending on the impurities in the gold.
Split into simpler sentences: The gold precipitate is then filtered out of the solution, mixed with fluxes, and smelted to form crude and impure bars. These bars are sent to a refinery to remove the copper and silver, the specific process used depending upon the impurities in the gold.