Pure natural calcium carbonate substrate. T-Rex Calci-Sand is a fine granular calciferous sand specially prepared to be the ideal reptile cage substrate for snakes lizards tortoises and turtles. T-Rex Calci-Sand is the only substrate for reptiles designed to be not only ingestible but digestible when swallowed. Many reptiles freely eat particles of sand and other substrates in an effort to gain the calcium that they require. T-Rex Calci-Sand is safe in direct contact with heating elements. It makes spot cleaning both easy and accurate. It clumps readily to wet waste material. It does not harbor mites nor the growth of molds or fungus.