Final answer:
The main resources mined and exported from the Spanish colonies to the Old World were silver and gold. These precious metals were a critical part of Spain's colonial economy and were heavily regulated by the Crown.
Step-by-step explanation:
The main resource mined and exported to the Old World from the Spanish colonies was silver, followed by gold. These precious metals were central to Spain's mercantilist economy, and significant quantities were extracted from locations such as the mountain of Potosà in South America. The Spanish Crown implemented a policy called the quinto, which dictated that one-fifth of all precious metals mined in the colonies was to be submitted to the Crown, emphasizing the importance of these resources. Although other commodities, such as sugar and cochineal, were also valuable, silver and gold remained the backbone of Spain's colonial wealth and were the primary target of their stringent trade regulations and economic policies.