Sky Blue is a limestone formed as a very fine-grained mud deposit with a relatively high percentage of organic matter. The sulfur content protects the stone against fungus. Some minor re-crystallization occurred, creating small calcite crystals that give it a slight glittery effect. The stone has very low porosity and permeability, making it suitable for swimming pools, driveways, and terraces. Selected tiles reflect the actual sky and cloud conditions, resulting in an amazing display of colors and brightness.