Mining for gold
watch youkon gold on discovery channel to see how larger operations get their gold concentrations from the test dirt digs when at bedrock.
red dirt usually has high concentration of gold
The golden triangle in BC is the best place in the world to get gold suposedly less than 3% of it has been discovered sofar. an ounce an hour can make a million dollars in gold per season with 3k gold prices.
mining moss works great for getting blackdirt and gold and holding onto it during large digs. rubber mats underneath it get more yeild.
handpumps with screens on the suction end are legal in most places.
venturi effect sluces with screens on the end should be ok too but dont quote me on that. (when the river is moving faster its easier on ecosystems please dont dredge slow or lowflow streams.)