WHILE PICKING MUD & ROCKS OFF OF CONVEYOR BELT, HE REACHED OUT TO PUSH A ROCK OFF THAT WAS HEAVIER THAN EXPECTED. THIS SPRAINED HIS RIGHT SHOULDER & HE NOTIFIED FELLOW EMPLOYEES & MANAGEMENT IMMEDIATELY. HE CHOSE NOT TO SEEK ANY MEDICAL ATTENTION UNTIL 07-12-2013 AFTER CONTINUED SORENESS PERSISTED.