The occurrence and distribution of rock and mineral deposits in Illinois are studied by the State Geological Survey Division of the Department of Registration and Education (fig. 20). In seeking new information concerning the state’s natural mineral resources, physical and chemical studies of useful rocks, minerals, and mineral products are made. Techniques and methods are developed and experiments are conducted to find and prepare Illinois’ mineral substances for use. The results of the Survey’s field and laboratory findings are published and made available to all citizens upon request. Much information that has not been published is in the open files of the Geological Survey where it may be examined by the public. Members of the Survey’s scientific and technical staff answer requests for information received by letter, telegram, telephone, or personal interview. Since the main ideas of geology are easy to understand and greatly increase one’s enjoyment and appreciation of the world in which we live, the Geological Survey publishes popular and educational booklets designed for the use of Illinois teachers and students. The Survey also distributes a labeled collection of rocks and minerals for class use in Illinois schools. Six geological science field trips are conducted each year throughout various sections of the state for teachers and interested laymen. Members of the Survey staff give illustrated lectures to organized groups about the geology and mineral resources of the state. [Illustration: Figure 20—Geological Survey offices are located in the Natural Resources Building, Urbana, Illinois.] WHAT IS THE CHARGE FOR THESE SERVICES? All of the Survey’s publications are distributed free to schools and teachers. Only topographic maps and certain base maps, which are prepared and printed by the U.S. Geological Survey in Washington, are sold at nominal prices. [Illustration: uncaptioned] [Illustration: Geologic column] Era General Types of Rocks Period or System and Thickness Epoch