This is an incredibly unique ring.
The cabochon is made from horn.
It is the tip of the horn and you can see all the streaks running along to the point. I usually find pure black tips and rarely ones with so many shades of browns.
The setting is made with sterling silver prongs.
The ring is adjustable so it would fit any size.
The top of the ring measures 3 cm in diameter and 1 cm tall.