Perlite in potting soil is a non-organic additive used to aerate the media. It appears as small, roundish white specks amid the other ingredients. As a soil additive (though less than perlite), vermiculite is also used for aeration, but they are not always interchangeable, although both are beneficial for rooting.
Other uses of perlite include masonry construction, cement, gypsum plasters, and loose-fill insulation. Perlite is also used in pharmaceuticals and municipal swimming pool water filtration as well as an abrasive in polishes, cleansers, and soaps.
Perlite Production
A perlite is a form of volcanic glass that is mined all over the world. It is an amorphous volcanic glass that has a relatively high water content, typically formed by the hydration of obsidian. It occurs naturally and has the unusual property of greatly expanding when heated sufficiently. It is an industrial mineral and a commercial product useful for its low density after processing.
Perlite is mined using open pit methods such as ripping or blasting, or both. If the perlite is soft and friable, brecciated, or extensively jointed, ripping is employed with significant cost savings. Blasting is required where perlite cannot be readily broken using rippers, but care must be taken to achieve fragmentation without the production resulting in excessive fines or oversized material.