Metamorphic Rocks are either igneous or sedimentary rocks whose texture, composition or appearance has been altered by heat and/or pressure. This process is called metamorphism. Any one, or two or more characters may be affected. Examples of metamorphism are: limestone changed to marble, sandstone to quartzite, shale to argillite, and granite to gneiss. This article describes some metamorphic observations in Colorado. It is written as a field guide.