Major coal deposits of India occur in

Major coal deposits of India occur in seams separated by sedimentary rocks. Today, coal formed by these processes is often found layered between other layers of sedimentary rock. Sedimentary rock is formed when sand, silt, clay, and similar materials are packed together under heavy pressure. In some cases, the coal layers may lie at or very near Earth's surface. In other cases, they may be buried thousands of feet underground. Coal seams usually range from no more than 3 to 200 feet (1 to 60 meters) in thickness.