To be clear this is gold that is physically possible to extract from everywhere in the earth— but without some sort of star-trek leap in technology not gold that is there by multiplying the accepted ppm all throughout (which would be ridiculously high, like in the hundreds of billions or trillions)
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Dude, there's gigantic zones on the earth that we have zero idea about and that are collectively managed by the supposedly "warring" goverenments.
It's naive to name any figure on how much available
We have a petty good idea about how much good can be economically extracted I'd say.
Of course could be upset by some giant leap in mining technology. But the calculation for bitcoin could also be upset by quantum and other technologies, so there's always that x factor there.