|Perlite is an inert material derived from a
naturally occurring volcanic rock, which when expanded by a
heating process, forms white, lightweight granules. Perlite is a
good soil amendment added to container potting mixes or other
growing medium, to promote moisture retention while allowing
good drainage. It is also useful to introduce air pockets in the
soil enhancing aeration as well as to keep the soil from
compacting. Perlite is chemically a sodium potassium aluminum
silicate. Its size ranges, but it is about as large as gravel.
See also vermiculite.