The geology of gravel in Indiana is related to glaciation. Gravel is found in ice-contact sediments, such as kame and esker deposits, and in outwash sediments, such as outwash-plain and valley-train deposits. The exploration for gravel requires the use of many tools; the most important of these tools are the topographic map, the soil map, and aerial photographs. Combining these three tools provides one of the best initial ways of isolating the favorable regions for gravel exploration from the unfavorable regions. The material that make up a gravel deposit reflect the parent rock in the source area, the way in which the rock particles were transported, and the depositional environment in which the rock particles were laid down. The results of the laboratory study of gravel show: (1) the major source area of Indiana gravels is close by the deposit, (2) mechanical breakdown during transportation is a more important factor than chemical solution, (3) gravel deposits do not result entirely from deposition in one transporting medium at any one time, (4) sandstone occurs in larger amounts in kame and esker deposits, (5) no single factor can account for the relationship between particle size and composition, and (6) most materials in gravel that make it undesirable for use as gravel aggregate increase in the smaller sizes in all gravel deposits.