Probably a dumb ? re: Irony Extrusion

Don't laugh, lol, but the last load I took in I had separated what i thought was aluminum but the guy took it out of the rest of the aluminum and weighed it as irony extrusion. A magnet didnt' stick to it and there were no screws in it so what made it ''Irony?'' If it had iron in it wouldn't a magnet have stuck to it? I tell ya, seems every time I take something it gets weighed different (I scrap out at 2 different places) so they tend to keep me confused!! I tried googling irony extrusion but it really didnt help explain how it was different or why. Thanks for any help!

Bring your own magnet. When they start checking everything have them show you. On some alum screen doors they have hinges that are alum not steel. Everytime I bring in some they state that it is irony due to the hinges I put my magnet on it and show them that it is an alum hinge. Keeps it out of the irony/furnace/mixed/dirty pile!

The hinges on screen doors have a steel rod holding the two halves together that's not really visible, maybe that was it.