Approximately 16x20x7.5mm faceted puffed black onyx gemstone oval beads. There are 18-22 beads per 16" strand. Black onyx might be somewhat smaller than other gemstones in this cut. Black Onyx. These beads have been enhanced to bring out their natural beauty. It is believed that onyx can sooth nervousness, and reduce stress. Questions? Call our friendly sales staff at 1-800-366-2156, or email us.