White Onyx Extra is quarried from a bedrock quarry. The slabs will have some clouds that are not as white, but overall they will be clean of any gold or rust veins. The slabs with the cleanest representation are priced in a higher category. Arizona Tile also stocks other white onyx slabs, such as White Onyx and White Onyx Extra A. Onyx is a sedimentary stone that is formed from carbonate minerals that are dissolved when dolomite sediments or limestone come into contact with water that has been heated due to volcanic activity, aiding in the formation of the Onyx. The layers of dolomite and limestone sediments accumulate, resulting in bands of various colors. This is similar to the process that results in the formation of stalagmites and stalactites in caves. It is a common characteristic for this stone to have voids in the raw material. Before the stone reaches the polishing stages, these voids are filled with an epoxy resin. Depending on how deep each void is, the resin may shrink as it dries, which will leave the surface of the filled area slightly lower than the rest. This does not affect the durability, maintenance or beauty of the stone. Due to the qualities of the stone, the slabs are book-matched; meaning slab one and slab two will be cut and polished to create a mirror image of each other. These are then kept in sequence, which allows for a consistent flow in pattern. Onyx slabs have transparent tendencies and, when backlit, will allow light to pass through, illuminating the stone. Because it is one of the softer and more fragile stones in the industry, careful maintenance of the slab is highly recommended. As a natural stone product, it is recommended that this be sealed to extend its longevity.