You Im not sure what they are, when I bought them on ebay a while ago, The heading said they were mother of pearl? but they were highly glossed and I couldn't really figure it out. They seem to be a form of shell but so highly glossed or maybe a type of ceramic.They are pretty- I a lot of them im my bead collection but I decided to part with a few. Ty for your inquiry. :P)
texture is a big clue when gauging MOP. I own a partenership with a man from french polynesia. I think they are pretty so i'll bid. They look great no matter what they are.