From Etsy seller SomethingLikeThat1:

This one of a kind wearable artwork is hand sculpted from polymer clay and finished with my finishing method to make it appear like glass. This unique necklace is beautifully finished and ready to use. no molds or pre-made shape are used, each piece starts from a lump of clay and finishes as you see in the images.

[Source: SomethingLikeThat1 on Etsy.com | Via Technabob]