Artisan-Made Natural Stone (Tourmaline?) & Brass Link Necklace

A modern piece made in San Francisco, though the texture of the stones and the handmade character of the links give it a really 70s craft fair feel. The stones seem to me to be tourmaline, and I don't know for sure, so please use your judgment on that point. They're strung on an 11.5" length of wire, which connects to a length of brass chain that's about 23". The diameter of the brass links is about .6" to give you a sense of scale. Can be worn as it comes, and you can also add your own charms or a statement pendant. In excellent condition, and I have been told that it was not worn.