While the reaction happens on the surface of iron, the presence of chemicals in rocks can influence the rate and extent of rust formation. For example:

* Salts in rocks can accelerate rust formation, leading to faster corrosion.

* Acids in rocks, especially those like sulfuric acid, can greatly speed up rusting.

* Moisture from rain or humidity can also contribute to the reaction.

So, it's not the rocks themselves that react to form rust, but rather the iron within them reacting with oxygen and water. However, the chemicals within the rocks can play a significant role in how quickly and easily this reaction occurs.