This thread is confusing me. I have almost no experience with pumice. Last year I did buy a bag of Dry Stall to use in a mix for some crocuses and fritillaries. The stuff which came out of the bag was pale gray-brown and very uniform in size: each piece was about the size of a grain of table salt or granulated sugar, but rounded rather than angular. It reminded me of celery seed. When the rest of you talk about dust, fines and small stuff, are you talking about particles smaller than the ones I've described? Did I pay $20 for a bag of something the rest of you sift out and throw away? Jim McKenney Montgomery County, Maryland, USA, USDA zone 7, where it seems to rain every day now.