>>13427567this is some dead reckoning, so you might have to conduct a small scale test first.
lenz's law is much more pronounced in copper, so if you drop a steady stream of these granules through a powerful changing magnetic field, then the copper granules should slow down (and heat up) more than the aluminium granules. if you can control the speed of flow of these granules, and have them fall at some kind of angle (say by using a conveyor belt and a jump) then you could sort the granules by speed. put buckets in two positions, one at distance the granules would go if they did not slow down significantly b/c of the magnetic field and the second bucket before then.
keep in mind i am just guessing here.
