I saw a statement somewhere once that claimed that all of the gold ever mined in the history of the world would fit into a 60’x60’ cube. But if annual global production is over 3,000 tons, I find that claim very hard to believe.
A 15 inch cube of gold weighs a ton. So 3,000 tons is almost 6,000 cubic feet per year. A 60’ x ‘60’ x 60’ cube is 216,000 square feet - so the claim is very plausible, even though it sounds far-fetched.
It kinda makes sense. A ton is a 14 inch cube. Very roughly, that 60x60 foot cube growing a foot taller each year would account for 3000 tons. And it’s easy to imagine that humanity mines more gold than ever before due to the massive machinery involved.
The 49ers did little more than scratch the surface of a continent and take the fairly easy stuff with the technology of the day.