People sell their Estate jewelry for many reasons. Perhaps it's a ring they bought many years ago and never wear anymore, or they've inherited their grandmother's necklace, and it's simply not their style. The old saying goes "One person's junk is another person's treasure," and that's the beauty of Estate jewelry. Everyone's personal style is a little bit different, so it's wonderful that you can sell an item you're not so fond of, knowing that there's someone out there who will fall in love with that very piece.
So, you're considering selling a piece of Estate jewelry (or "Antique" if it is over 100 years old). The most important thing is: make sure you go to a trusted source to get it appraised and subsequently sell it. Soliciting a few different opinions is always a good idea, especially with something that could be very valuable. Also look online or at jewelry stores to the prices of pieces similar to yours. Keep in mind that you will most likely receive less than that because whoever you're selling to needs to make a profit. Also consider the condition of your piece. Items needing repair usually have less value than jewelry in good condition, and the price offered to you will reflect that. If you have a certificate of authenticity for your piece (a certified diamond for example), bring it to the appraisal.