Black Gemstone Necklace Black Quartz Necklace 14kGF. This gorgeous necklace is made with black quartz gemstones and 14 k GF beads, lobster clasp and chain extender. Necklace is approximately 17-20” including the 14k gold filled lobster claw clasp and extender chain. The bracelet is 7 1/2”. This set looks quite expensive due to the beautiful natural stones and 14k gold filled beads.