This is a 1" Lee Valley rare-earth magnet. This is what happens with a moment of inattention and allowing one loose magnet to collide with another.
Their insert says in part "All of our rare-earth magnets are strong and should be treated with respect.
Their attractive forces can cause loose magnets to unite with such impact that their edges can chip."
Their insert says in part "All of our rare-earth magnets are strong and should be treated with respect.
Their attractive forces can cause loose magnets to unite with such impact that their edges can chip."