Perlite is a mined mineral that is crushed then expanded under high temperature. Perlite is white in color, very light weight, but has high water holding capacity and high aeration properties.
Sources There are negligible differences in grades as far as crop performance is concerned.
Use horticultural grade perlite, coarse or medium size. Price and sales support might vary among perlite suppliers. Availability Perlite can be purchased ready to use in pre-made, lay flat bags, approximately three feet long, six to eight inches wide, and four inches tall. Perlite also can be purchased in bulk bags or in medium bags of about four cubic feet. Growers can then purchase rolls of polyethylene sleeving material and make up their own growing bags.