Roman Soldier Cameo on Locket engraved 1880

by Cynthia Royer
(Harrisburg, PA)

What can you tell me about the significance of this cameo locket? It is engraved from a husband to a wife 12/25/1880 on the back. The cameo is a Roman soldier. Why is the cameo black? Has it deteriorated in color or has it always been like that?

Also, do you think the locket is gold and what might something like this be worth? It opens and closes perfectly but the edges around the locket seem to be somewhat darkened.

Thanks so much! This is a piece from my grandmother's estate.