Characterized by kaleidoscopic colors unfolding across undulating layers, onyx is a precious gemstone material that is imbued with intrigue. The lightweight and luminous stone has a long and rich history of use—its earliest appearances can be traced back to ancient Egypt and Greece. With an elegant and opulent aesthetic defined by dramatic bands of color that playfully combine with the stone’s subtle glow, onyx is employed across an array of applications from pottery and jewelry to interior elements. “Onyx is always fascinating to people because it is so different compared to other stone varieties that we work with,” says Josh Levinson of Artistic Tile. “It is prized for its beautiful aesthetic with amazing colors and veining.” The information below provides a brief overview of onyx’s unique formation and composition as well as its colorways and characteristics.
Formation and Composition
Though occasionally mistaken for marble, the mineral makeup of onyx offers a distinct look that is distinguished by layered bands of lustrous, translucent minerals. Onyx has a lightweight and porous composition comprised of the silicate mineral chalcedony—a cryptocrystalline form of quartz with a waxy sheen that can assume many colors. “Onyx is a calcium carbonate-based stone and a type of sedimentary stone that is very different,” says Levinson. “What is unique about onyx is that it is formed in subterranean caves in limestone-rich areas where water percolates down and picks up the calcium carbonate. Onyx is formed out of the stalagmites and stalactites in the caves. Over time, these grow together and eventually fill out the whole cave with onyx.”
Exposed to both pressure and heat for an extended period of time, onyx features varied bands of chalcedony in alternating colors that are fused together in a fluid pattern. Onyx can be identified by bands that run parallel to one another, unlike the chaotic banding that commonly occurs within its chalcedony counterpart agate. The bands form from the cooling of added minerals mixed with silica. This, in turn, causes the minerals to deposit in delicate layers. Moreover, Onyx is often considered to have a delicate composition that can be easily etched and scratched. “Onyx is a beautiful but relatively fragile material,” says Levinson. “Since it is a calcium carbonate stone, onyx has very small grain sizes and is susceptible to chemical and acid attacks, as well as mechanical abrasion and scratching.” As such, polished onyx is not well-suited for interior applications that are heavily trafficked. However, honed onyx may hold up better to abrasion. “Another limiting factor for onyx is that because of the way it is formed, the blocks are somewhat small, which results in smaller slabs that oftentimes have more fracturing and fissures and may be more challenging to fabricate.”
Colorways and Characteristics
Onyx’s wavy bands commonly come in naturally formed shades of black and white that stretch across the stone. Of course, onyx can also be seen in an inspiring array of iridescent hues—ranging from pastel pinks and rich reds to vivid yellows and oranges, and nearly all the colors in between. “Onyx appears in lots of colors such as vanillas, grays, ambers, greens, and more,” says Levinson. “Some of the colors have more of a vein cut appearance while some have a crosscut and flowery appearance.”
Onyx showcases a shimmering and luminous luster that can contradict with the commonly understood composition of stone. “It is typically translucent so it can often be backlit since and it transmits the light very well,” says Levinson. Touting a semitransparent texture that stands in contrast to the opacity of other stones, onyx often emits an ethereal radiance when exposed to light, which makes for an ideal and illustrious interior element. “Onyx has a unique beauty that is unparalleled by other types of natural stone,” adds Levinson.