Take some dust particles whose size is big. Bring a magnet near them. They do not get attracted to the magnet and thus we conclude that they are non-magnetic. However, when you grind the particles to the smallest particle size you can go to (any practical size such as .5mm or .2mm) and then bring a magnet near it - the particles get attracted to the magnet!
Conclusion: The particles are, in-fact, magnetic
Why does this happen?
Is it possible that the dust particles have become magnetic with the decrease in size due to their para-magnetic property taking over (takes over because as the particle size decreases, there are less chances of the dipoles being cancelled in the material, since there are less dipoles in the material. So the dipoles can align in one direction more easily than in a bigger material)? (My Explanation)
I did find a link on the net related to this, however it was not that helpful: Non-Magnetic Aluminium Particles get attracted to magnet when they are cut into smaller pieces!
Please help! Thanks a lot!