Approximately 12x5.5mm faceted puffed squares. There are 31-37 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 said that wearing onyx can help in public speaking. Questions? Call our friendly sales staff at 1-800-366-2156, or email us.