I can't find pumice on the east coast, and like Bonaventure I have used perlite extensively for many years. Not only has the particle size deteriorated significantly, but virtually all the brands available from the big box stores now add fertilizer to the perlite, making it worse than useless. I don't want to overfertilize bulbs and succulents, and I definitely don't want to add unknown amounts of fertilizer to carnivorous plants and terrestrial orchids. This year, I have started using stalite (marketed as "Permatill" and "VoleBloc") as a substitute for perlite. It is an expanded shale that is mined here in the southeast, and I have used it for years to break up our clay soil. Results in pots have so far been good. The particle size is uniform, with little dust or fines, and roots seem to like growing into it. Since it is dark grey, it looks nicer than perlite. It doesn't float and makes a fairly attractive top dressing. Nick Durham, NC Zone 7 On Tue, Jul 2, 2013 at 8:56 AM, Bonaventure Magrys wrote: > I can tell you for perlite with fine particles, it was bad news in the > way I used it. The stuff coming from the big box stores here in New Jersey, > USA, is loaded with dust and fines, the brand M******Gro has really gone to > sh*t. > > I had used it primarily for Cypripediums, mixed with other inorganic > material or cactus,palm,citrus potting mix. Even after being sprayed down > and washed through a sieve outdoors, whereupon it loses half of its volume, > I found that its addition turned the mix late in the season to a solid > concrete like consistency, completely unfriable in one thick clump with no > air spaces. > > Bonaventure Magrys >