Supreme Perlite Medium Soil Mix Grade Perlite consists of particles primarily between 1/16” – 1/4” (1 – 4 mm). Used in nursery seedling mixes, stormwater filtration and DOT approved media filter mixes. Supreme Perlite NATURAL VOLCANIC PERLITE® products are made exclusively from 100% naturally occurring volcanic glass. Our perlite products are sterile, ultra-lightweight, non-toxic, durable, incombustible, insulating, asbestos-free, pH-neutral, and are compatible with most other substances.