If semi-precious stones have their own cache of best kept secrets, then one of them is definitely Larimar. It's an extremely rare precious stone that has only been found in one very small location on the planet, a remote mountain range of the Dominican Republic in the Caribbean.
This is a beautiful double strand combined with freshwater pearls and baby blue Swarovski crystals. It measures 17" with 1/12" extender. The clasp is Sterling Silver (.925).