Are there diamonds anywhere in N. America besides Arkansas? Good luck.
I also have to ask, what brought up this question? Probably only way to do this would be to dry all material first, than spread some, not alot, on a cookie sheet painted flat black and a diamond should stand out amidst the black sand. Time consuming but does the job when dealing with smaller classified material. Specific gravity of black sand being 5.2-5.26 and diamonds at 3.1-3.53, black sand will always be heavier.