Complex sentence: In 1967 the Chilean government bought a 51% stake in the mine and founded Sociedad Minera El Teniente, and under this agreement a new concentrator was built, and the mine expanded its production to per day.
Split into simpler sentences: In 1967 the Chilean government bought a 51% stake in the mine and founded Sociedad Minera El Teniente. Under this agreement a new concentrator was built, and the mine expanded its production to per day.