White Cloud is a limestone composed of bio-turbated muddy lime. The stone is very well packed, resulting in low porosity and permeability. Calcite crystals embedded in the fine muddy lime are protected against external chemicals, making it suitable for swimming pool applications. The high percentage of muddy lime gives the stone a degree of flexibility, making it suitable for paving and driveway applications. Precipitation on top of the stone may occur if the water is hard, air pollution is strong, and water circulation/filtering is inadequate. Saltwater pools especially need good chemical balances.