I posted on this topic a while back. A quick search will find the thread.
Ebay, where I ran across them, has some info in the listings.
I am looking for any information on these stones. I have been finding them on the land that I live on and have recently had them identified. They are very large compared to the ones I see on-line(14") How should they be used? What is their history? How did they get to N. CA? Any insight is appreciated, Thank you.