Millidarcy vs. Darcy — What's the Difference?

A unit of area that is 1/1000 darcy. Symbol mD.

A unit used to measure the permeability of porous substances such as soil, equal to the passage of 1 cubic centimeter of fluid having a viscosity of 1 centipoise for 1 second under the pressure of 1 atmosphere through a medium having a volume of 1 cubic centimeter.

A (non SI) unit of permeability used in measuring the permeability of porous mediums such as sand.