Perlite, in its naturally occurring form, is a dense, amorphous, hydrated volcanic glass, generally of rhyolitic composition (sodium potassium aluminum silicate). Because of its commercial applications, perlite has a dual nomenclature in the industry. It is known by the same name as both the naturally occurring rock and, after processing and thermal expansion, as the lightweight aggregate (Kadey 1983).
Aggregate in plasters, loose-fill insulation, filtration medium, paint filler, oil-well drilling muds, inert packing materials.
