EE WAS OPERATING JOY 10SC32 SHUTTLE CAR ON RT 4 SECTION. HE WAS TRAMMING TO THE FEEDER WHEN SHUTTLE CAR STRUCK A ROCK AT THE #6 INTERSECTION. WHEN HE BACKED SHUTTLE CAR UP, A PIECE OF ROCK 40"" X 12""X 10"" ROLLED OUT FROM THE RIB ONTO THE DECK & STRUCK HIS RT FOOT. X-RAYS WERE NEGATIVE. EE WAS SEEN BY A SPECIALIST ON JULY 8 & ADVISED TO REMAIN AWAY FROM WORK.