Soil for Cob?

Hi everyone..  I've  read quite a bit of info on here about  testing your soil for clay content, where to look for clay soil, etc. to make cob. 

I own property in West Texas that is desert, with mostly sandy soil, no clay. 

Does anyone know if road base that can be ordered from quarries,  contains clay?  I know that for earthbag building,  a lot of times people  will order cheap road base to fill the bags.  I know there are also different grades of road base....but not familiar enough to know the difference.

Just looking at my options for building a small cabin on my property in the desert...

TejasTerry

From my research into the same thing, I can suggest looking for clay with pottery clubs in your area, garden centers may have earth with high clay content. I am in similar position but clay content is smaller than sand can be 15% to 50% clay so 85% sand to 50 %.

Make some test bricks first though, gathering materials is an adventure it seems. Good luck.