I grew up in the gold country (high school was NUHS the Miners) and the streets were literally paved in gold, the ore wasn't processed nearly so fine as they can today. There is plenty of gold in them thar hills still.
How about the dude pulling over 3.5 oz. per 100 yds. of dirt daily? Almost $4K a day...that'll keep the sluice box running.
I've spelunked in many a mine/cave back in the day it's interesting stuff for sure.