Onyx - Color, Types, and Properties

Onyx

Onyx is a banded variety of chalcedony, which is a type of microcrystalline quartz. Onyx is characterized by its parallel bands of different colors. The most common color combination is black and white, but onyx can also be found in other colors, such as red, brown, and green.

Onxy stone. Photo credit: UCL Geology Collections

 Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved chaotic bands and onyx has parallel bands. Its multi-layered structure is similar to that of agates. When the stone has a black base and a white upper layer, it's called onyx. When the base is brown, it is called sardonyx while carnelian-onyx has a red base.

Onyx comes through Latin (of the same spelling), from the Ancient Greek ὄνυξ, meaning "claw" or "fingernail". Onyx with flesh-colored and white bands can sometimes resemble a fingernail.

Onyx Types and Colors

Onyx isn’t an actual family of gemstones, rather a term used to describe layered stones that contain bands of black and white.

Black Onyx

The most sought-after type, black onyx, exhibits deep black bands, often with white or gray streaks. It is widely used in jewelry and ornamental objects due to its elegant and timeless appeal.

White Onyx

This variant showcases bands of white, often with a translucent appearance. White onyx is cherished for its purity and is commonly used in carvings and sculptures.

Green Onyx

Characterized by captivating green bands, this type of onyx exudes a sense of tranquility. It is popular in jewelry and decorative pieces.

Red Onyx

With vibrant red bands, red onyx is a rare and luxurious variation. It is frequently used in high-end jewelry and unique interior designs.

Sardonyx

Sardonyx is a variety of onyx that exhibits bands of brownish-red (sard) and white or black. It is highly prized for its distinctive appearance and is frequently used in cameos and intaglios.

Onxy agate with Quartz from Uruguay, at the Mineralogy Gallery in Paris. Photo: Camille Gévaudan

Artificial treatments have been used since ancient times to produce both the black color in "black onyx" and the reds and yellows in sardonyx. Most "black onyx" on the market is artificially colored.

Onyx is the traditional birthstone for February. It is associated with relaxation and comfort.

Onyx is popular as a carving stone, since clever use of alternating bands of black and white can create a highly appealing carving.

Onyx is a gemstone found in various regions of the world including Greece, Yemen, Uruguay, Argentina, Australia, Brazil, Canada, China, Czech Republic, Germany, Pakistan, India, Indonesia, Madagascar, Latin America, the UK, and various states in the US.

Onyx is a variety or type of:  Agate, which is a variety of Chalcedony, which is a variety of Quartz.

Onyx from Brazil. Photo: James St. John

Onyx Properties

Crystal System: Trigonal
Color: Various
Cleavage: no cleavage
Fracture: Onyx has a conchoidal fracture, which means that it breaks into smooth, curved surfaces that resemble the inside of a seashell.
Mohs scale hardness: 6.5–7
Luster: Vitreous, silky
Streak: White
Specific gravity: 2.55–2.70 g/cm³

Natural Onxy. Photo credit: UCL Geology Collections