EMPLOYEE WAS STRUCK BY A BOLT THAT FELL OUT OF THE ROOF WHILE GETTING HIS BOLT TIGHTNER WRENCH TO TORQUE THE BOLT. CAUSE OF THIS INJURY WAS SAFETY AWARENESS. COMPLIANCE WITH RULES/REGS WAS NOT A FACTOR; PROTECTIVE EQUIP. WAS BEING WORN. MINER PROFICIENCY A FACTOR; MINING EQUIP/SYSTEM COULD BE A FACTOR.