Hi Cynthia, Permatill is one of the trade name for stalite, an expanded slate product. It's also sold as vole-bloc. Like perlite, it is inert and porous, but it does not float. It's a nice neutral grey, and the particle size is fairly uniform, pea sized or smaller. I don't have easy access to pumice, but I would image in that permatill would work in most of the same applications. I use in mixes and also as a top dressing. Nick On Tue, Oct 27, 2015 at 8:34 AM, Cynthia Mueller <cynthiasbulbs@hotmail.com> wrote: > Nick, could you describe 'permatill' for us? I know the term but not the > actual composition. > > Cynthia W Mueller > >