Perlite is siliceous, or containing silicon, volcanic rock. Perlite is heated in order to cause it to expand to almost twenty times its size and volume, resulting in a white, puffy material. Gardeners, to improve the drainage of the soil, especially soil used in container planting, frequently use perlite. It also great for aeration of the soil. There are two types of perlite usually available on the market. One is "coarse" and the other is "fine." The coarse texture is the one that the vast majority of gardeners need to use. The fine-textured perlite is almost like a powder and really does not serve the purpose of improving drainage and aerating the soil. In addition, some companies actually include other materials; i.e., fertilizer, in their perlite. Any gardener will want pure perlite for their plantings and do not want any extra materials added. It would seem that buying perlite would be a quite easy, which it can be if you know where to look.
Check Lowe's, Home Depot, and Wal-Mart for perlite. Each of these large chain stores usually carry perlite. They are, therefore, the best places to check first. However, you may find that they have vermiculite instead of perlite. Vermiculite is made from a mineral, which at times contains impurities, specifically asbestos. In addition, the process by which vermiculite is made can result in fibers that can be harmful if inhaled. This means that you will want to think twice about substituting vermiculite for the perlite.
Check the major gardening centers in your area. This may sound rather obvious; however, you should focus on the word "major." Most small, locally-owned garden centers or nurseries will not usually carry such materials as perlite. Larger gardening centers normally will.
Check Reed's Green House on the internet at www.reedsgreenhouse.com. They sell perlite online and offer pure perlite that does not contain fillers.
Check with your local agricultural county extension. These extensions are supported by area universities and offer assistance to the public, usually free-of-charge. (Note: The Master Gardener program, which focuses on volunteering their services in the community, is sponsored by these county extensions; and any Master Gardener will be willing to help you in your quest.) Any of the employees and/or members of your county extension should be able to help you locate perlite.