EE WAS ENGAGED IN SCOOPING UP A PILE OF LOOSE ROCK TO LOAD INTO DUMP TRUCK WHEN THE BUCKET OF FRONT END LOADER STRUCK A SOLID ROCK LEDGE JERKING EE FORWARD INSIDE OF CAB. EE WAS WEARING SEAT B ELT RESTRAINT AT THE TIME OF INCIDENT. BELIEVED POSSIBLY THAT THE IMPACT FROM HITTING THE SOLID ROCK LEDGE MAY HAVE CAUSED THE INJURY. EE WAS UNAWARE OF THE EXISTING CONDITIONS AT THE TIME OF