Please don't forget to get back to us! I know I for one am curious as to what the stone is. My first thought was a synthetic Spinel and my second thought was a Sapphire, lab or natural. It is a cool color, thats for sure.
Question...does Peridot go that yellow/light in tone? Only reason I mention that is because the stone does seem to glow in the lower lighted picture, and isn't that a sign of Peridot? I know the OP mentioned that Peridot was her G'mothers birthstone...
I'm going to put in my guess that it is a synthetic spinel colored to look like your grandmother's birthstone, peridot. I'm thinking back to my high school days when we could pick our birthstone to be in our class rings. Synthetic stones were called "spinel" and that is part of the reason that real spinel had a bad reputation for so many years.
It's really pretty and looks good on your hand. The colored halo is unique! I'm not sure what it is. I have seen synthetic spinel that color in older pieces of jewelry before ( at least it will be durable if it is ). But it could be something else too.
I don't want this thread to get forgotten, cause I am dying to find out what the stone is...if we are right that it is synthetic Spinel, or if it is something more exotic..
Chrisa, I'd be suprised if it was a peridot since it's not a new stone and yet has very little damage - I would expect it to be a material relatively high up on the Mohs. Would opt for Chrysobel over peridot as a natural possibility...