An issue is the definition of a “gold mine”. Many mines that produce gold are composite ores, other valuable metals are extracted at the same, usually silver or copper but occasionally other metals. Mining of pure gold ores can be pretty clean as heavy metal mining goes, it is the other elements that tend to drag along messier chemistry.
That aside, gold mining has been moving outside of the developed world for decades, most operating mines in the US (and the US produces prodigious amounts of gold) were already grandfathered in under prior laws. You’d have to ban gold mining in countries that aren’t going to play along. Also, even in the developed world, there is a lot of opportunity for black market gold production. A large fraction in the US is small producers and reserve studies are incentivized to be heavily sandbagged. For example, while the US produces a lot of gold, the origin of at least 30% of it is not entirely clear. Laundering off-book gold ore would be a piece of cake. It is a fascinating business.
I don't care much about Musk mission to mars but with the cost declines in rocket launches in the next few years I really hope asteroid mining becomes a thing.
Harmful, dangerous industrial activity is always best relegated to undeveloped countries. That way it can kill the largest number of exploited workers and produce maximal environmental damage.
I think that the idea is that developed countries have no "need" for it, while developing countries could and will benefit from maximally exploiting their natural resources to develop as quickly as possible. There's a good point in your comment (that the process exploiting natural resources is more harmful in developing countries, and so might not be worth the tradeoff for faster development), but it's buried under sarcasm and lack of charity. We could have a more productive discussion without it.
It would also be ideal for developed countries to ban any multinational corporations from exploiting undeveloped countries for their gold. Tricky to enforce however possibly.
There is a World Gold Council that puts out stats on use of gold each year and by far the biggest use is for investment. Jewelry and industrial uses have been on the decline for decades.
That aside, gold mining has been moving outside of the developed world for decades, most operating mines in the US (and the US produces prodigious amounts of gold) were already grandfathered in under prior laws. You’d have to ban gold mining in countries that aren’t going to play along. Also, even in the developed world, there is a lot of opportunity for black market gold production. A large fraction in the US is small producers and reserve studies are incentivized to be heavily sandbagged. For example, while the US produces a lot of gold, the origin of at least 30% of it is not entirely clear. Laundering off-book gold ore would be a piece of cake. It is a fascinating business.