I would just ask to see the bag the Red Clay came from to make the pots. Typically Powdered Red clay comes in 40# bags for about $20 in the States. This is pure 100% clay.
Most hobby store clays have polymers in them so they can be bake in a home oven or air dried. Those are much more expensive.
If he does have a 40# bag you can see to read the label, offer him $5 bucks for a 2 pounds of the powdered clay. You'll be way happier working with powdered clay than smashing up clay pots.
BTW - For what it would cost to analyzed a sample you could UPS a 40# bag to your home.
Last edited by DogFish; 11-27-2012 at 02:36 PM.