Antique Cameo value?

by Tamara D
(Indiana, USA)

I have a cameo brooch that I was given a couple of years ago. I know it is made of shell and is encased in gold. She has a flower and three leaves in her hair as well as diamond studded crescent moon in her hair. The back has a c shaped clasp that is open. I know it's old but I need to know what era its from and the value of the brooch. Can anyone help with this information?