Shale is a clay-dehydrated rock that can be divided into carbonaceous shale, calcareous shale, sandy shale, and siliceous shale. Shale is weak against weathering. The shale is impervious to water and often becomes a water barrier in the distribution of groundwater. There are many shale classifications, and they are relatively widely used. For example, iron shale may become iron ore, oil shale can refine oil, and black shale can be used as an indicator formation for petroleum. And shales can also be used as raw materials for brick, cement, ceramsite and other products.