Onyx

Onyx is a variety of chalcedony, a microcrystalline form of quartz, composed mainly of silicon dioxide (SiO₂). It is characterized by parallel, regular bands, usually of contrasting colors: white, black, brown, red, or gray. It forms through successive deposits of silica in rock cavities and fissures.

Marble onyx, also called calcareous onyx, is an ornamental rock composed mainly of calcite (CaCO₃) or aragonite, and not quartz. It is distinguished by its white, cream, yellow, green, brown, or orange colors, often arranged in translucent bands, veins, and patterns. It typically forms through the precipitation of calcium carbonate in springs, cavities, or hydrothermal environments.