Thank you! The vendor I bought them from advertised them as glass, but they feel a little too lightweight. I didn't put glass in the description because I'm not 100% sure.
Yes, I tried the contact sound, and I still can't tell with 100% certainty. The sound is a bit too dull for glass and too sharp for plastic. I don't want to try the heat test because it might damage the bead, and they're too pretty. My best guess would be lucite or bakelite but I'm not an expert.