Palmetto Vermiculite Grade A-3 is a premium, coarse particle size material meeting ASTM C516 Type 1, Grade 2 specifications.This OMRI-listed material is great for organic gardenging. It is widely used as a component of growing media for professional growers. Additionally, the material is used as a cover for seed topping. The particle size and absence of fines makes the material ideal for packaging smaller boxes of hazardous chemicals for air transport in accordance with IATA Regulations. Coarseness and size may vary depending on mine harvested from.