The capacity of a rock to transmit a fluid such as ground water is called permeability. The permeability of a rock or sediment indicates how freely water passes through the open spaces in it.
For a rock to be permeable, the open spaces must be connected. Permeability is affected by the size and sorting of the particles that make up a rock or sediment. The larger and more consistently sorted the particles are, the more permeable the rock or sediment tends to be.
The most permeable rocks are those composed of coarse particles such as sandstone.
