Onyx is often confused with marbles, yet it is a significantly different rock type. Onyx is a sedimentary rock, formed as stalactites and stalagmites in cave interiors. This formation method results in the cryptocrystalline construction of the rock fabric, and it is the size and uniformity of these crystals that contribute to the classic translucent property of most onyx varieties. While vulnerable to chemical and abrasive attack, the decorative appeal of onyx is perhaps unsurpassed by any other material.
Due to the way onyx is formed via dripping limestone that then re-forms into new stone, every single slab of onyx will have a unique pattern to it. It comes in a variety of colors, each with different styles and swirls of accent colors (generally called “veining.”)