Origin of "Pan Out" and "Flash in The Pan"

During the gold rush people were trying to make fortune panning rivers, looking for nuggets of gold. But few rivers ever panned out enough of the stuff to make them rich, but the practice did enrich the English language with this phrase, plus, another one: "Flash in the pan", a hint of something valuable that turns out to be short-lived and disappointing, probably from the flashes of what were thought to be chunks of gold in your pan, but turn out to be other, worthless metals.