Ok Gentlemen!
As usual you are all trying to overthink all of this stuff. The bottom line is that for years people knew of "solid surface" as Corian and that is how it was defined. Now that there are soooooo many different manufacturers offering good products and our industry is rapidly growing with more and more countertop material choices, we as fabricators have to provide our customers with a definition of the types of countertops that we offer.
The bottom line, Corian, Staron, Hi-Macs, Avonite....and the like are solid surface materials. Caesarstone, Silestone, Zodiaq and the like are quartz surfaces or Estone. Granite, soapstone, travertine, marble are natural stone surfaces.
There are your definitions. Nothing technical about it, just laymen's terms.
Just my thoughts!
Valerie