It seems that there is once again confusion on "Dry Stall" and "Stall Dry", two different products. Dry Stall is pure pumice, I believe it is from the same mine near Death Valley that supplies horticultural pumice to most of North America. Stall Dry is a calcined clay (I prefer Turface MVP, less dust and slower breakdown). It is obviously easy to confuse the two product names. Just this weekend I bought two bags of Dry Stall at my local feed store, and they loaded Stall Dry in my car! m 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