This resource provides a 5E style lesson (Engage, Explore, Explain, Elaborate, Evaluate) over the rock cycle, including a single-period lab using crayons to model the cycle.  It’s often a difficult concept for students to imagine that over millions of years, one kind of rock will change into another kind of rock.  This lab allows students to see the changes taking place, and learn important qualities of each type of rock and how they are formed.Photo:  Rainbow of Crayon Shavings by Richie Girardin via Flickr