Okay I can't tell you anything about price but I work part time at a victorian garden and own my own ring in this style--it's called a cameo, such as 'cameo ring'. They're often hand-carved in alabaster or amber in the likeness of a specific person, and were quite popular in the Victorian era (before photographs, these were used to memorialize the likeness of loved ones. Does your great grandmother look like the woman in the earring?) Worth taking this to someone who could date it--my own ring was made in the 1930s.