Perlite has many uses and is often used in horticulture. It is a hard highly porous material made by super-heating volcanic glass. It is mixed into the soil to help improve aeration and drainage. Perlite is rough so water and nutrients gather in its crevices, making moisture and nutrients available to the plant. Perlite is a naturally occurring siliceous rock and as such, is not toxic.
Perlite is also used as a lightweight aggregate material in concrete. Perlite offers thermal insulation, fire resistance and other desirable properties when used in cement.
Perlite is also used in reptile incubation. It's a great incubation medium for reptile eggs and also for raising the humidity in incubators.
It is advisable to wear a dust mask and goggles when working with perlite to avoid throat or eye irritation.