My understanding is that over the course of several hundred years, the Spanish removed thousands of tons of gold and silver from their colonies in the Americas and shipped them back to Spain.
Putting aside shipwrecks, privateer attacks, etc., I'm curious what happened to the gold and silver that made it back to Spain. Was it melted down? Turned into jewelry, coins, various other things? Were these things hoarded in the royal treasury or spent?
Finally, do we know where all this treasure is today? Did it just disappear into general circulation? Could my aunt's gold necklace be made in part from looted Spanish gold?
They were spent: much of it circulated to sources outside of Spain to the point where it contributed to and accelerated general rise in prices of commodities in what is known as the price revolution in the 16th century.
The Hapsburg who ruled Spain and Austria made a bid to dominate Europe through diplomacy and the force of arms and paid for a large portion of it using the gains from new world gold and silver as well as gains from the Asian spice trade. Military expenditure took up to 80% of the Hapsburg budget in the 16th century, while total expenditured grew by 80%. The Spanish army increased 5-fold, from 20,000 men to 100,000.
This mean gold and silver were minted into coins and flowed from the treasury into the pockets of mercenaries and soldiers, shipbuilders and arm manufacturers, who in turn would have spent them on other goods and put them into circulation in the general economy. Not only Spain, but later on England minted coins from new world gold, in the form of the Doubloon and the golden Sovereign respectively.
Even the immense wealth generated by the new world turned out not to be sufficient for the fiscal needs of the Hapsburg however. The army of the Flanders mutinied more than a dozen times owing to the lack of payment, and Spain declared bankruptcy 4 times in the 16th century.
Source: States Versus Markets: The Emergence of a Global Economy By Herman M. Schwartz
Early Modern Europe, 1450-1789 By Merry E. Wiesner