Onyx
| Property | Details |
|---|
| Mineral | Chalcedony (quartz family) |
| Mohs Hardness | 6.5 – 7 |
| Refractive Index | 1.530 – 1.539 |
| Major Sources | Brazil, India, Madagascar, Uruguay |
| Treatments | Dyeing to achieve uniform black (standard, permanent) |
Overview
Onyx is a variety of chalcedony most commonly known in its solid black form. Black onyx has been used in jewelry and carvings since antiquity and remains one of the most popular black gemstones for men's jewelry, signet rings, cuff links, and bold fashion pieces. Its opaque, uniformly black surface provides a dramatic backdrop for diamonds and creates striking contrast in two-tone designs.
Varieties
Black onyx: The most recognized form, used extensively in men's and fashion jewelry. Sardonyx: A banded variety combining black onyx with reddish-brown sard, traditionally used for cameo carvings. Most commercial black onyx is dyed to achieve a uniform deep black color, a permanent and long-accepted treatment.
Care & Cleaning
Onyx ranks 6.5 to 7 on the Mohs scale and is durable enough for most jewelry. Clean with warm soapy water and a soft cloth. Avoid harsh chemicals and prolonged soaking.
Frequently Asked Questions
Is black onyx naturally black?
Most commercial black onyx is dyed to achieve its uniform, deep black color. Natural onyx is typically banded in various shades. The dyeing process for black onyx has been practiced for thousands of years (since Roman times) and is permanent, stable, and universally accepted in the gem trade. The treatment is so standard that disclosure is often considered unnecessary, though reputable jewelers will note it upon request.
What is sardonyx?
Sardonyx is a banded variety of onyx that combines layers of black or dark brown onyx with reddish-brown sard (a type of chalcedony). It has been used since antiquity for carved cameos and intaglios because the contrasting color layers allow artisans to create detailed relief images. Sardonyx is the original August birthstone and was prized by Roman soldiers as a talisman of courage.
Is onyx good for men's jewelry?
Black onyx is one of the most popular gemstones for men's jewelry and has been for centuries. Its bold, uniform black color works well in signet rings, cuff links, tie bars, bracelets, and pendants. Onyx pairs beautifully with gold, silver, and stainless steel. At 6.5 to 7 on the Mohs scale, it is durable enough for daily wear in most jewelry types, though it should be protected from hard impacts in ring settings.
How durable is onyx for everyday wear?
Onyx ranks 6.5 to 7 on the Mohs hardness scale, making it moderately durable. It will resist scratching from most everyday materials but can be scratched by harder gemstones and abrasives. Onyx is tough and unlikely to chip or break under normal conditions. For rings worn daily, choose a design with a slightly recessed stone to protect the surface. Onyx earrings, pendants, and cuff links are excellent for everyday wear.
What is the difference between onyx and obsidian?
Onyx is a variety of chalcedony (microcrystalline quartz) formed from layered deposits of silica. Obsidian is a volcanic glass formed when lava cools rapidly. Both can appear solid black, but they are fundamentally different materials. Onyx is harder (6.5-7 vs 5-5.5 Mohs), more durable, and takes a smoother polish. Obsidian often has a glassy luster and can display iridescent sheen (rainbow obsidian) or golden specks (gold sheen obsidian).
Specialty & Collector Gemstones