Complex sentence: The mines were exploited in an extremely efficient and witty way according to the technology available (Jovanovic 1980, Craddock 1995, Timberlake 2003), the entire convenient mineral was cleaned and the abandon shafts carefully refilled with gangue and rocks (Mohen 1992; 85).
Split into simpler sentences: The mines were exploited in extremely efficient and clever ways, according to the technology available (Jovanovic 1980, Craddock 1995, Timberlake 2003). The entire convenient mineral was collected and the abandon shafts carefully refilled with gangue and rocks (Mohen 1992; 85).