Where I work in the Arkansas River the gold can be so fine I would describe it as feathery. I found that the most abundant gold is the flood gold that is deposited and moved each year. I get my MD-20 and probe the downstream side of rocks, and when I get either a beep for gold or a "boing" for black sand accumulation, I dig just the imediate area right behind the rock. Don't go deeper than the rock, this is just targeting the temporary flood gold right behind the rock. Then run the material in a low water velocity sluice like a Grizzly Sluice III, or a Gold Cradle. You'll get more fine gold than you know what to do with. When I use my Blue Bowl, I run a cup of concentrates like normal. Then, after it washes out the light stuff and the black sand, your left with the visible gold by the center cone. Turn off the water, snuffer that, then turn the water valve really high. The sudden current will make your Blue Bowl dislodge and push fines that got stuck on the bottom, and you'll only really see them when they start moving in wave twords the center cone. They are only visible when they are clustered together. Do this several times. Also you have to use a flashlight or a headlamp to actually see the fines.
