>Perlite is a volcanic product that is composed primarily of silica.
>Most people use it to replace sand.
I would add that it is available in many hardware/lumber stores
because it is used as an additive to plaster...primarily to "lighten"
the plaster. It is quite "dusty" in my experience, so I try to
handle it as little as possible when dry as it is very irritating.
Moistened, perlite is a wonderful growing medium for plants
needing nutrients at an almost nil level.
ross
Ross Koning Internet: Koning@ecsuc.ctstateu.edu
Biology Department Phone: (203)-465-5327
Eastern CT State University Fax: (203)-465-5213
Willimantic, CT 06226 USA