Hi - thought I'd reply as I have just had an antique garnet ring appraised in-store. If the garnets are backed with gold or silver foil, the ring could actually be older, it might even be Antique Victorian. Now if the ring was made in the 19th century, which means the ring is older still, the garnets would not have been faceted but cut "en cabochon" which are round-dome like cabochon stones.
It would be interesting to know how many garnets are in the ring and what the setting looks like? I think this will play a part in the value. I recently had my antique garnet ring appraised for $1500 however the gold work on the shoulders is quite intricate. Good Luck! Sue J