Sulfur is a common starting material for the Contact process. What is a source of sulfur?
Pyrite is an ore that can be mined from the ground. It is made of sulfur and iron. Its formula is
The pyrite is burned in excess oxygen to produce sulfur dioxide. The balanced chemical equation for this process is:
As you can see here, a lot of sulfur dioxide is produced, and also iron(III) oxide, and becomes rust when it comes into exposure to water.
For the full process, visit: