Copper is sometimes just taken out of the ground and shaped into objects. But most copper is not in a metal form in the ground. Chalcopyrite is the main copper ore. It is heated with air to separate the iron as iron(II) oxide. Some copper(I) oxide is made. Sulfur dioxide is also made. Then silicon dioxide is added, which reacts with the iron(II) oxide to make a liquid which is drained. Now only copper and sulfide are left. The copper sulfide reacts with air to make copper metal and sulfur dioxide. Some copper sulfide reacts with the copper(I) oxide to make copper and sulfur dioxide. This makes impure copper.