Hi, I ran into this thread and want to offer a clarification: as I understand it, Dri-Stall is technically a 'calcined clay' (fired but not to the point of full vitrification). This is why the material does not break down like aggregated clay in its natural state. The physical characteristics of the clay ensure that it retains its high CEC after firing (which also burns out any organic matter.) I am looking for insight and observations (or even better, scholarly/technical references) that might guide me on choosing proportions of calcined clay and horticultural pumice when preparing a media for long-term container growth of specimen plants. Here locally (Santa Cruz County, CA) some of the bonsai enthusiasts are HUGE advocates for Dri-Stall, I have them to thank for turning me onto this material. If these folks trust their precious plants to Dri-Stall I consider this a solid endorsement. I appreciate any insight and suggestions, thanks very much! Dave Moore