Why doesn't a magnet pick up shards of hard disk platter?

[RisingSun]

I intentionally shattered an old hard disk platter. Then I used several magnets to try to pick up the pieces, but the magnets wouldn't pick them up. Why?

 

[FuryRosewood]

because there is a thin coating on the platter that actually has magnetism to it, and its probably so minute it wont allow you to pick up the mass of the platter