When Carlos brings a mystery rock to school, he hopes Ms. Frizzle will tell him what kind of rock it is. But the Friz doesn't like to tell when she can show....That's how the class ends up on a wild rock hunt in the Wild West, trying to solve a mineral mystery! They take a stagecoach ride, pan for precious gems, and even explore an old mine. Sure, the going gets a little rough at times--but this road trip rocks!