36″ x 24″ full color laminated poster. This is an outstanding rock identification chart! The introduction explains that each type of rock is the result of a specific mixture of minerals subjected to a clearly defined geological process. It shows and describes the most common rock-forming minerals and variations that occur within rock types. The bulk of the poster is divided into three sections, one for each rock type: igneous, sedimentary, and metamorphic. An illustration shows how they are made, and a photograph shows a natural formation. A dozen other photographs show representative specimens. Each is accompanied by an informative caption citing identifying characteristics and common variations. A bonus section shows and explains some of the more specialized and popular rock forms, such as geodes, concretions, agates, and meteorites. This is a great poster for earth science classes. Rock collectors find it invaluable for quick reference.