That thing obviously has been forced to the surface by high pressure water, probably in a volcanic vent.
Not much likelihood of finding another one near by.
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It is a Placer.
It was pushed up with molten rock many, many moons ago, but it certainly has traveled along ways since it broke away from it’s original source... being smooth like that! Had to be quite the flow to move that huge dense hunk.
I also would not bet against others being found near it... gold concentrates together and nuggets are often found in patches when metal detecting.