At first glance, it looks like some bullshit the soil company puts in as non-soil filler so they can screw you out of the soil you paid for. Well maybe it is. Anyway, it is made from a mined mineral, unexpanded perlite. Perlite is volcanic glass that has become hydrated over time, that is, it absorbed water. To make expanded perlite, they heat it, like, really lots, and it puffs out. It's kind of like when they make puffed wheat or rice, or how a popcorn is made. The mineral bubbles up from the expansion of the water to its gaseous state. I like to call the crap popcorn rock.