Approximately 35mm round black onyx gemstone donuts. 34-35 x 5-6mm with large hole. Black Onyx. These beads have been enhanced to bring out their natural beauty. It is said that wearing onyx can help in public speaking. Gemstone donuts are often used in jewelry as pendants and focal pieces. Questions? Call our friendly sales staff at 1-800-366-2156, or email us.