EMPLOYEE WAS OPERATING A ROOF BOLTING MACHINE. HE WAS STANDING BESIDE THE BOOM OF THE MACHINE GETTING READY TO START DRILLING A HOLE. STONE FELL FROM THE TOP, HIT BOOM OF MACHINE AND THEN STRU CK EMPLOYEE'S RIGHT THIGH. NO DAMAGE TO THE MINING OPERATION. THE INJURY DID NOT INVOLVE COMPLIANCE, JOB SKILLS, PROFICIENCY, TRAINING, ALTITUDE, PROTECTIVE ITEMS, OR PROTECTIVE DEVICES.