My husband works for an iron ore and coal mining company, and our recent trip to Marquette was a business conference for him in which we tagged along. One morning we had a three-hour behind the scenes field trip of an iron ore mine. We followed the entire value chain of the product from the moment it is dug out of the ground up until when it is processed into purchasable pellets. This included seeing the loaders, haulers, processing plant, etc. It was a very educational morning.
The picture below shows the kids standing in front of a tire from a hauler (pictured above). Each tire costs $60,000!