Complex sentence: In 1766, the Spanish colonists of Tumacacori discovered silver near their mission town, immediately afterward the priests had the local Opata and Tohono O'odham native Americans begin mining, thus establishing the Opata Mine.
Split into simpler sentences: In 1766, the Spanish colonists of Tumacacori discovered silver near their mission town. Immediately afterward the priests had the local Opata and Tohono O'odham natives begin mining, thus establishing the Opata Mine.