It was - and is - an effective means to extract gold nuggets and gold flakes from surface deposits where there is a supply of water. So the answer is, it worked as long as there was gold at the surface and a source of water. Perhaps I am missing the intent of your question?

While prospectors often used the easily-transportable pan, nineteenth-century placer miners employed larger implements once they were certain a viable deposit existed, but these "rockers" and sluices" worked in the same way, namely washing away lighter dirt and then picking through what remained with tweezers to pick out the gold. Sometimes miners of the periods also used mercury to form an amalgam, which was cooked or squeezed off to leave the gold, but that was not as common since the cost of the mercury would reduce profit. (People did not fully appreciate the health risk.)

I suspect I'm missing something in your question, however, so let me know.