Even if you are a pavement only short track fan, you gotta check this out:
senoiaraceway.com/new-gumbo-clay-down-and-ready-for-open-practice/
This track is about an hour south of Atlanta. It was dirt for a long time, then paved for about twenty years I believe. It went back to red clay about 5 years ago.
The owners had some problems with the surface last year, and they sourced some grey “gumbo” clay from south Georgia. I’ve never heard of that before, and have never seen anything like it! I"m really looking forward to catching a race here this summer.