The old Yuba dredge piles can be good hunting.......most had screens in the trommels ranging from 5/8 to 3/4 inch holes....anything bigger went on through the trommel and on the stacker belt and got dumped. And some of the old adit and shaft dump piles can be very worthwhile as they were following the main vein and some little side offshoots would get mucked on out and dumped over the side.
Nice lookin stuff you are finding.