Employee was bolting on the left side of the Joy miner at 13+28 in H4 section. A rock that measured 3""x4.5"" up to 8"" thick fell and landed on the rib protector door, sliding down and hitting the employee on the upper back. Employee returned to work on 7/21/23 and was then diagnosed with concussion like symptoms on 7/24/23. No other part 50.20-5 apply.