This Earth science animation demonstrates the formation of a cast and mold fossil to middle and high school students. The introduction provides a brief description of the process. The animation shows how a shelled animal becomes buried in mud that eventually turns into stone. The shell dissolves and is replaced by minerals and, when the layers of rock are split, a cast and mold fossil is revealed. Movie controls allow students to repeat, pause, or step through the animation, which can give students more time to analyze the images. Copyright 2005 Eisenhower National Clearinghouse