Cameo from France

This exquisite cameo was given to my mother by my father's mother to welcome her to the family. Since my father was the first in the family to marry someone not of French heritage. My grandmother was born approx 1900. The necklace had been handed down to her but I do not know how old it is or what it is made of but the setting is so beautiful (and quite clearly a good quality solid gold). It is about 1" high. I do not have the chain & do not recall one. If anyone can help me know more I would greatly appreciate it. Truly by far the most beautiful & tasteful one I've ever seen.