What Type of Sedimentary Rock Is Permeable?

Limestone and sandstone are usually permeable. The rule of thumb is that coarse-grained rock is more permeable than fine-grained rock. Rock also needs a fairly low level of cementation to be permeable.

All permeable rocks have relatively high porosity, which is the percentage of the rock's volume that consists of open space. Sedimentary rocks consisting of well-rounded coarse grains are usually porous; fine-grained rocks and rocks made of poorly sorted sediments have low porosity because the fine grains fill in most of the available space. Cements or binding agents also fill in pore space. For rock to be permeable, pores must be interconnected with large enough channels to permit the passage of water.