What is Perlite?

Perlite is a naturally occurring siliceous rock that expands 4 to 20 times its original size when rapidly heated to approximately 1,700 °F.,A non-crystalline silicate that occurs naturally in volcanic ash deposits;

Perlite consists of small beads of volcanic glass that can be "popped," i.e., heated until it expands into a styrofoam-like material that is used in construction products and soil conditioners. Crystalline silica not bound to other minerals is "free" silica. Silicates are minerals in which silicon and oxygen are combined with other elements.