Copper (pure copper) is produced by melting copper ore in a melting furnace, adding silicic acid and oxygen to eliminate sulfur and iron, removing the oxygen, and electrolyzing the ore to remove impurities. The impurities include gold, silver, platinum, palladium, and sulfuric acid. There are several types of copper, and tin or zinc can be added to pure copper to make bronze or brass. Copper is highly workable and resistant to rust that it is always used for items which can be used for a long time, and usually it is used as a material for ships, construction, and daily necessities. It is also widely used in electronic devices due to its high thermal conductivity and electrical conductivity.