Back when I was a kid and first started going to antique shops, thrift stores, and vintage shops on my own, I could never figure out why in god’s name people were paying (what seemed like to me) exorbitant prices for plastic bangles. Oh naïve Scout Savant, they weren’t plastic - they were bakelite! And what is this proto-plastic known as bakelite? Originally used for things that gave off a lot of heat (such as tube radios, car parts, electrical components), bakelite become a jewelry trend all on its own.
So how do you test for bakelite? One tried and true way involves rubbing the piece against your hand to heat it up - if it’s bakelite, it will release a smell that I can only describe as “like formaldehyde.” Another way to test is using simichrome - a tiny dot on cloth then rubbed on the piece will cause the pink simichrome to leave a yellow stain. There are plenty of other methods, but these are the least damaging and most reliable. There’s a chance other ways to test the pieces could cause damage. Some folks will use a hot pin to test, a hot pin won’t penetrate a bakelite piece but could damage other non-bakelite pieces.
OK, I know what you're thinking, that’s all well and good, but where can I find bakelite? This is the great news right here - you can usually find them in junk jewelry lots, placed in there by folks not familiar with the material or mistakenly identified as cheap plastic. Go rummage around in the jewelry section of your favorite thrift shop (don’t forget your gloves), and be amazed at how much bakelite is hiding among the broken costume jewelry and cheap rings that turn your fingers green.