Understanding where gold actually concentrates in a stream

Gold is roughly 19 times denser than water, which is why moving water sorts and concentrates it in specific, predictable spots rather than spreading it evenly across a streambed. The inside curve of a bend is a classic spot, current slows there and drops heavier material. Behind large boulders and other obstructions is another, the water slows immediately downstream of anything that disrupts the flow. Cracks and depressions in exposed bedrock, once the overlying gravel is cleared away, can trap gold that has been working its way down through the gravel for a very long time, sometimes called false bedrock when it is not the true bottom. The base of gravel bars is another common concentration point. None of this is new information, it is the same basic placer geology prospectors have relied on for well over a century, but understanding why it works makes it much easier to read a new stream instead of panning at random.