Use two hooks for hanging a large mirror. Each hook should be capable of supporting the mirror's weight, to be safe. Because you are hanging the mirror on brick, you'll need wall anchors. Metal or plastic will do.
Drill two holes on an even line in the brick. If the line isn't even, the mirror will hang at a crooked angle. The exact placement can vary. In general, consider the full length of the mirror and place the holes somewhere between 1/4 to 1/3 of the distance in from each side. Drill the holes to match the size of the anchors. While drilling holes, be sure to wear safety goggles and use the drill according to the manufacturer's directions.
Insert the anchors into the holes.
Thread the hooks onto the screws and insert the screws into the anchors. Tighten the screws down.
Hang the mirror onto the two hooks. When hanging large and heavy mirrors, have someone to help you to avoid straining your back or having an accident.