Perlite is a lightweight granular material that is white in color and is used in horticultural applications to improve soil drainage and aeration. It is made from a naturally occurring mineral that is a type of volcanic glass, created when the volcanic obsidian glass gets saturated with water over a long time. Perlite typically contains 70-75% silicon dioxide, aluminum oxide, sodium oxide, potassium oxide, iron oxide, magnesium oxide, calcium oxide, and 3-5% water. The mined raw material is heated to temperatures between 1400° and 1800° F, causing it to expand and pop like popcorn, resulting in the airy, sphere-like particles we know as perlite. Perlite is typically bright white, with the look and feel of Styrofoam, but closer inspection reveals a texture closer to pumice. It is a non-renewable resource, and the world reserves of perlite are estimated at 700 million tonnes.