Why did Spanish conquistadores search the Americas?

Spain was the earliest of the European powers to exploit the resources of the New World. The "conquistadors" were explorers and conquerors of the ancient Native American empires. The purpose of expending the money and manpower to do this was based on two factors:

1. Gold and silver were easily transferred by ship to Spain, and

2. It seemed clear that there would be mines to gather even more precious metal wealth, and also gems & valuable mineral deposits.

3. Very importantly Spain wished to enlarge its sphere of influence in the world.