The symbol looks too small. Take a picture and upload it, then out the link in one of our comments. Or if a mod can help. They can delete this post and you can post a new one so we can see it and put the link there.
I can't make out the symbol but the necklace looks like sterling silver.. It is an old piece and silver was used in jewelry. You can send that picture to www.skinners.com and they can help you out. They do free appraisals. Once you get to the sight, follow the directions. You can call first and describe it . They might tell you to just email the picture..I use them all the time now. Skinners is an auction house by the way.