Magic sand is a special type of hydrophobic sand. It can be blue, green, or red in colour. Magic Sand was originally developed to trap ocean oil spills near the shore. This would be done by sprinkling Magic Sand on floating petroleum, which would then mix with the oil and make it heavy enough to sink. However, due to the expense of production, it is not being used for this purpose.
Magic sand was marketed by Nickelodeon and Mattel as Sqand.
Due to its water repellence, grains of the sand will adhere to each other in the presence of water. When sprinkling grains onto the surface of water, they will at first form a "sand raft," until the weight of the agglomerate is large enough to break the surface tension. The mass will then sink to the bottom as a single object. When immersed, the sand forms columns in order to reduce the surface area in contact with water. As soon as the sand is taken out of water, it is completely dry and flows freely.
Though blue, green, or red in colour, immersed columns of magic sand appear silvery because of a layer of air that forms around the sand.
These remarkable properties are achieved by covering ordinary beach sand with tiny particles of pure silica and exposing them to vapors of trimethylhydroxysilane (CH3)3SiOH, a silicon compound. Upon exposure, the trimethylsilane compound bonds to the silica particles while forming water. The exteriors of the sand grains are thus coated with hydrophobic groups.