Anyone know?

Bob,

What department are you finding this in? 

Since silica is the base mineral which weathers to kaolinite, I would advise against the use of these in place of turface. This is due to the soft nature of kaolinite and ease to fracture. Most of us know kaolinite in the home environment as porcelain figurines.  

It's in Walmart in their automotive section.  It's used as an adsorbent for liquid spills.  It's quartz related.  I'm not too worried about fractures as it wont see much abuse.  But thanks for the bump  :)

hi Bob,
it might be similar to Napa, also for the same automotive use.
and napa is used by some bonsai enthusiasts as part of their soil-less planting medium

found this
http://forums2.gardenweb.com/forums/load/contain/msg0814421119289.html