Welcome to the forum. It's difficult to be certain from the photographs, and it would be easier to be sure if we could see one lit from behind. But from what I can see, these appear to be blue glass discs. If authentic (there are some copies around as there are of just about everything) they come from the Samon Valley in Burma. In her book Early Landscapes of Myanmar, Elizabeth Moore shows some on page 113. She cites villagers from Ywa-din-gon as saying that these are found generally close to the waists of skeletal remains. They date from the late first millennium BCE.

Cheers,

Will