I.E. was operating 239CM on the Right Side of Unit #2. I.E. set the CM over to start on the 1st cut out of the Right Side. After doing so, I.E. knelt down in the corner, which had been cut when the slider was turned for Entry 8-7. A rock measuring approx. 6' x 4'4"" x 3"" fell from a height of 6.5', traveled approx. 39"", and struck I.E. in the Right Shoulder.