WHILE EMPLOYEE WAS OPERATING CONTINUOUS MINER, APIECE OF ROCK (19 1/2 X 22"" WITH ONE END SHARPENED) FELL FROM BETWEEN THE ROOF BOLTS OF THE MINEROOF. IT STRUCK HIS LEFT HAND WITH WHICH HE WAS USING TO OPERATE THE REMOTE CONTROL. THE ROCK CAUSED AN ABRASION TO THE TOP OF HIS HAND & THE 2ND, 3RD, & 5TH FINGER. THE FACE AREA WAS ABOUT 8' HIGH WHERE THE ROCK FELL.