Almost certain it is green turquoise. I have a fairly decent amount of raw turquoise and there are a few green pieces in it. The design also looks fairly modern to me, but I am not an expert.
No matter what it is a nice piece, and I would assume it is silver, a lot of the modern Native Americans still work with silver. Not sure if it will be a full 925 quality, but it might be worth more for what it is, than it's silver content. Is there a reservation nearby? Might look to see if they have a museum and if they could tell you more about it.