Have you seen these type of clip on earrings?

I enjoy thrifting and when something caught my eyes I will surely pay attention to it. I found these clip-on earrings because the blue color stand out big time. My challenge is I cant find any jewelry maker in the back as well not knowing if these are real semi precious stones or something. The stones feels smooth like a glass. It looks very well made and not light. Any info is always appreciated.