Featured Strange fastening on necklace

That resin is still used for traditional Dutch bead necklaces, those stunning multi-row coral, garnet or carnelian ones with the huge gold filigree clasps.

 

Great find! I am no expert but I also think it is coral. Besides, these golden elements on the clasp also point to coral.

 

I would also say they look very like white coral - a good way to check is to put a tiny drop of lemon juice on one of the smaller inconspicuous beads and watch with your loupe to see if any bubbles begin to appear under the juice on the surface of the bead. Glass or stone won't effervesce but coral will.

 

Since the other candidate here is conch shell, not sure the citric acid test can differentiate.

 

Of course - I don’t think the beads really look like conch - I have a few queen conch necklaces and the banding on the beads is quite visible but you’re right, conch would also effervesce.

 

This sounds like helmet shell beads. If you scroll down just about midway in this page there are photos showing beads of all 3 kinds you can use for comparison:

https://cameotimes.com/index.php/reference/materials-guide?start=1