I don't toss anything anymore, I used to but they're just getting to hard to get ahold of. A few pix, one of a handmade with mica & another a Peltier NLR with Aventurine. No !! not all Iridescence marbles are throw away, iridescence is a good indicator of 'Vacor" or (Mega) a newer marble all are made in Mexico but some do have value !! If you have a loupe you'll be able to tell air bubbles from mica. Don't feel bad Gina I have been duped before also. You're in the right place now, people here will help ya out, no one is here to judge anyone else, just share what we know.
An antique German Handmade with mica flakes
A Peltier NLR Tiger with Aventurine, this pic is in the sunlight
Same marble under normal indoor lighting using a daylight bulb