Petrology, a component of geology, is the study of rocks. If you could name all the rocks in the app right off the bat, you probably already knew that! If you are a earth science student, however - or just want to learn more about rocks - this is a good place to start. The game is broken down by the 3 rock types - igneous, sedimentary, and metamorphic. There are photos of rocks in each rock group to identify. The Learn button helps you study before playing. Have fun and learn at the same time! Teachers should check this out, too.