What is onyx?
By Jared James · Last updated 21 May 2026
Definition
Onyx is a variety of chalcedony quartz that forms with parallel banding of alternating colours, most commonly black and white. In jewellery, the term almost always refers to solid black onyx, which is the pure black bands of this material, sometimes dyed to achieve an even, intense black. It has a glassy surface, takes an excellent polish, and is hard-wearing at around 7 on the Mohs scale. Black onyx is widely used in men's jewellery, mourning jewellery and statement pieces, and it has been carved and worn for thousands of years.
Frequently asked questions
- Is black onyx naturally black?
- Black onyx is typically dyed from lighter chalcedony to achieve its uniform black colour. This is a long-standing, accepted and stable treatment that does not affect quality or value in the way some other treatments do. Natural solid black banding does occur but commercial black onyx is almost always treated.
- Is onyx a precious stone?
- Onyx is classed as a semi-precious gemstone. It is affordable and widely available, though quality carving in antique pieces can command significant prices. What makes it desirable is its deep, rich black colour and the quality of its polish rather than rarity.
- How do you care for black onyx jewellery?
- Onyx is reasonably durable and handles everyday wear well. Clean it with warm soapy water and a soft cloth, avoid harsh chemicals and ultrasonic cleaners, and store it away from harder stones that could scratch the surface.
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