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