The study of earth science concepts frequently requires the use of reference documents and graphic representations of complex systems and processes. Geologists, as well as students, are required to describe and identify geological materials based upon peer-reviewed and widely accepted classification systems. In the support of the Indiana Geological Survey's mission to disseminate information, the documents provided within these pages are meant to enhance the learning experience of a novice or as quick reference sheets for experienced geologists. In addition, frequently requested graphic organizers and diagrams are included. Users should expect periodic updates or modifications to these documents.