Made from 150-million-year-old fossilized dinosaur bone, this Monique Péan necklace (www.moniquepean.com) also features black tourmaline, 18-karat pink gold, and diamonds. The bone material—which dates to the Jurassic period and was discovered in the Colorado Plateau, near the Four Corners region of the southwestern United States—is naturally purplish, the result of mineral permeation. Each smooth, triangular-cut black tourmaline displays fine gray lines across its surface. The necklace, which is priced at $22,035, exemplifies Péan’s use of recycled material in her designs: The gold was recovered from older jewelry pieces. For other designs, the New York–based jeweler incorporates fossilized woolly-mammoth tusk and walrus ivory that are nearly 150,000 years old.