What would be the effects on the world if Spanish gold was never looted in bulk from the New World? Not to say that North America doesn't get colonized but that the Aztecs and Incas have some degree of success resisting as opposed to OTL's perfect storm. Personally I'm interested in the lack of economic stimulus that the rest of Europe got from Spain combined with the lack of local silver/gold sources.
First the latest search confirm that american gold was never used for money until 1700's. Not "just a little", no one piece analyzed showed a similarity with american metal.
Second, it is evaluated that at least 1/3 of the american gold disappered on sea. No. Not in the hands of corsairs and privateers. Litteraly in the sea.
The economical stimulus wasn't that important for Europe (except the taxation) and it was more directed towards italian bankers. The port of Genoa recieved flotilla of gold to pay the interest of the loan taken by spanish monarchs. American gold directly passed on the paiment of european wars.
Now, it certainly gave a stimulus for America itself, funding and stimuling the colonization, the creation of latifundiae in the XVII.
And, more surprisingly, it helped greatly the trade with China, that searched silver ore.
So, Spain managed to buy tea, silk, etc. from a power that didn't wanted something else. It's basically why, and not a particular greed in itself for the metal, the Portuguese created a road to Potosi trough Brazil to "borrow" some of surplus.
Talking about mines, the climax of Zatatecas and Potosi production was reached in the XVII/XVIII thanks to more rational (aka, more mercure) mining.