Ultra Purification of a Metal is Done by:
Zone Melting purification process is known as Ultra-Purification of Metal.
What is Zone Melting Purification?
In this process a small region of metal is melted and this molted zone is moved along the crystal or metal rod. In this zone impurities are easily melted at forward edge and leaves behind more pure metal. This melting process is done slowly with full metal rod. It will produce highly pure metal.
All other methods like leaching, smelting and slugging can provide pure metal but not of high quality.