sentences:  The Empire Mine opened in 1963 and was expanded in the mid- and late-1970s; the Pioneer Pellet Plant was opened in 1965 to pelletize the underground ore from the Mather B Mine in Negaunee.In 1974 the Tilden Mine opened in Ishpeming.This mine was and is the only mine in the world with the ability to produce both hematite and magnetite pellets.