If you're looking for natural onyx beads you've come to the right place! What is onyx? Onyx refers to a variety of the silicate mineral chalcedony. Agate and onyx are similar in that they are both composed of similar material, but agates are banded while onyx is not. The distinction of agate vs onyx, however, is not black and white, with many varieties of sardonyx agate which takes the onyx name but show banding characteristics. At Tejas Beads, we carry a large assortment of shapes and colors of natural onyx and sardonyx including red, brown, and black onyx gemstone beads. We hope you enjoy shopping in our onyx gemstone beads collection.