Onyx is a banded variety of Calcite. The colors of its bands range from white to almost every color except shades of purple, blue and black. It is used for vases, bowls, beads, cabochons and other items. This type is found in Mexico and Pakistan and is often carved and polished into various items. This material is much more readily available and softer than the gemstone commonly called Black Onyx which is a silica gem.