Onyx is a unique natural stone formed from dripstone deposits in limestone caves. When water drips from the cave’s stalactites and stalagmites and evaporates, a substance known as calcium carbonate is left behind. As a result it causes the stone’s colourful veins, swirls, and patterns that are unique to onyx. Onyx is crystalline stone, and often translucent – which means it allows for light to pass through. The degree of translucency varies among onyx slabs and is dependent on the colour, thickness and surface finish.