Perlite is an amorphous form of volcanic glass. It is sometimes called expanded pyrite and has the nickname “volcanic popcorn” and I will discuss why in the next section. If you look at a garden perlite under a microscope, you will see that it is quite porous. The voids inside the perlite help to store nutrients and some moisture that the plant may need, but drain excess water. It is non-toxic, clean, disease-free and extremely lightweight and easy to handle. Perlite is often used in industrial settings as well as in the garden. It is often mixed into products such as lightweight plasters, ceiling tiles or masonry as a stabiliser or insulator. It is also popular as a leaching agent and is often used to leach grain or other solids from beer or used in the biochemical industry.