Employee had just finished cutting the crosscut between #2 and #3 entry. He backed the miner into the last open crosscut and had hung a loop of miner cable and hose on the tail of the miner. He mistakingly hit the conveyer button on the remote box which started conveyer and ejected a rock measuring3'7"" length 1'8"" width 1'5"" thick. Rock struck him on lower shin.