J.T. Baker 5003 #20-40 Grade Silica Sand 50 lb- Silica sand is finely broken down quartz stone. This type of sand is designed to use with pool filtration systems to safely and effectively remove harmful containments and small debris. The rough and coarse sand is able to improve water quality over long periods of time by slowly removing pollutants such as dirt, hair, leaves and more. This process ensures that the pool water is clean and healthy, and ready to be enjoyed year-round.