Last updated
CategoryOxide mineral
(repeating unit)
Silica (silicon dioxide, SiO2)
Crystal system Trigonal
Formula mass 60 g/mol
Cleavage no cleavage
Fracture Uneven, conchoidal
Mohs scale hardness6.5–7
Luster Vitreous, silky
Streak White
Diaphaneity Translucent
Specific gravity 2.55–2.70
Optical propertiesUniaxial/+
Refractive index 1.530 to 1.543
References [1] [2]

Onyx primarily refers to the parallel banded variety of chalcedony, a silicate mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands: agate has curved bands and onyx has parallel bands. The colors of its bands range from black to almost every color. Commonly, specimens of onyx contain bands of black and/or white. [3] Onyx, as a descriptive term, has also been applied to parallel banded varieties of alabaster, marble, calcite, obsidian and opal, and misleadingly to materials with contorted banding, such as "Cave Onyx" and "Mexican Onyx". [4] [5] [6]



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. [7] The English word "nail" is cognate with the Greek word.


Red onyx (also called "Sardonyx") Red onyx - Handicraft.jpg
Red onyx (also called "Sardonyx")
Black onyx with bands of colors Black Onyx.jpg
Black onyx with bands of colors

Onyx is formed of bands of chalcedony in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel to one another, as opposed to the more chaotic banding that often occurs in agates. [8]

Sardonyx is a variant in which the colored bands are sard (shades of red) rather than black. Black onyx is perhaps the most famous variety, but is not as common as onyx with colored bands. 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. [9] [10]

Imitations and treatments

The name has also commonly been used to label other banded materials, such as banded calcite found in Mexico, India, and other places, and often carved, polished and sold. This material is much softer than true onyx, and much more readily available. The majority of carved items sold as "onyx" today are this carbonate material. [1] [11]

Artificial onyx types have also been produced from common chalcedony and plain agates. The first-century naturalist Pliny the Elder described these techniques being used in Roman times. [12] Treatments for producing black and other colours include soaking or boiling chalcedony in sugar solutions, then treating with sulfuric or hydrochloric acid to carbonise sugars which had been absorbed into the top layers of the stone. [10] [13] These techniques are still used, as well as other dyeing treatments, and most so-called "black onyx" sold is artificially treated. [14] In addition to dye treatments, heating and treatment with nitric acid have been used to lighten or eliminate undesirable colours. [10]

Geographic occurrence

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. [1]

Historical use

The Gemma Augustea is a Roman cameo produced 9-12 AD and carved in a two-layered onyx gem (19 x 23 cm) Kunsthistorisches Museum Vienna June 2006 031.jpg
The Gemma Augustea is a Roman cameo produced 9–12 AD and carved in a two-layered onyx gem (19 × 23 cm)

It has a long history of use for hardstone carving and jewelry, where it is usually cut as a cabochon or into beads. It has also been used for intaglio and hardstone cameo engraved gems, where the bands make the image contrast with the ground. [15] Some onyx is natural but much of the material in commerce is produced by the staining of agate. [16]

Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items. [17] Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos. [18]

Brazilian green onyx was often used as plinths for art deco sculptures created in the 1920s and 1930s. The German sculptor Ferdinand Preiss used Brazilian green onyx for the base on the majority of his chryselephantine sculptures. [19] Green onyx was also used for trays and pin dishes – produced mainly in Austria – often with small bronze animals or figures attached. [20]

Onyx is mentioned in the Bible many times. [21] Sardonyx (onyx in which white layers alternate with sard - a brownish color) is mentioned in the Bible as well. [22]

Onyx was known to the Ancient Greeks and Romans. [23] The first-century naturalist Pliny the Elder described both type of onyx and various artificial treatment techniques in his Naturalis Historia . [12]

Slabs of onyx (from the Atlas Mountains) were famously used by Mies van der Rohe in Villa Tugendhat at Brno (completed 1930) to create a shimmering semi-translucent interior wall. [24] [25]

The Hôtel de la Païva in Paris is noted for its yellow onyx décor, and the new Mariinsky Theatre Second Stage in St.Petersburg uses yellow onyx in the lobby.

Throne of Jahangir Agra Fort - Jahangir's Throne.JPG
Throne of Jahangir

The Throne of Jahangir (Urdu: Takht-i-Jahangir) was made of black onyx. It was built by Mughal emperor Jahangir (31 August 1569 – 28 October 1627) in 1602 and is located at the Diwan-i-Khas (hall of private audience) at the Red Fort in Agra, Uttar Pradesh, India.


The ancient Romans entered battle carrying amulets of sardonyx engraved with Mars, the god of war. This was believed to bestow courage in battle. In Renaissance Europe, wearing sardonyx was believed to bestow eloquence. [26] A traditional Persian belief is that it helped with epilepsy. [27] Sardonyx was traditionally used by English midwives to ease childbirth by laying it between the breasts of the mother. [28]

See also

Related Research Articles

<span class="mw-page-title-main">Agate</span> Rock consisting of cryptocrystalline silica alternating with microgranular quartz

Agate is a common rock formation, consisting of chalcedony and quartz as its primary components, with a wide variety of colors. Agates are primarily formed within volcanic and metamorphic rocks. The ornamental use of agate was common in Ancient Greece, in assorted jewelry and in the seal stones of Greek warriors, while bead necklaces with pierced and polished agate date back to the 3rd millennium BCE in the Indus Valley civilisation.

<span class="mw-page-title-main">Quartz</span> Mineral made of silicon and oxygen

Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2. Quartz is the second most abundant mineral in Earth's continental crust, behind feldspar.

<span class="mw-page-title-main">Topaz</span> Silicate mineral

Topaz is a silicate mineral of aluminium and fluorine with the chemical formula Al2SiO4(F,OH)2. It is used as a gemstone in jewelry and other adornments. Common topaz in its natural state is colorless, though trace element impurities can make it pale blue or golden brown to yellow orange. Topaz is often treated with heat or radiation to make it a deep blue, reddish-orange, pale green, pink, or purple.

<span class="mw-page-title-main">Tourmaline</span> Cyclosilicate mineral group

Tourmaline is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. Tourmaline is a gemstone and can be found in a wide variety of colors.

<span class="mw-page-title-main">Chalcedony</span> Microcrystalline varieties of silica, may contain moganite as well

Chalcedony ( kal-SED-ə-nee, or KAL-sə-doh-nee) is a cryptocrystalline form of silica, composed of very fine intergrowths of quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, while moganite is monoclinic. Chalcedony's standard chemical structure (based on the chemical structure of quartz) is SiO2 (silicon dioxide).

<span class="mw-page-title-main">Carnelian</span> Yellow-red chalcedony variety

Carnelian is a brownish-red mineral commonly used as a semi-precious gemstone. Similar to carnelian is sard, which is generally harder and darker. Both carnelian and sard are varieties of the silica mineral chalcedony colored by impurities of iron oxide. The color can vary greatly, ranging from pale orange to an intense almost-black coloration. Significant localities include Yanacodo (Peru); Ratnapura ; and Thailand. It has been found in Indonesia, Brazil, India, Russia (Siberia), and Germany.

<span class="mw-page-title-main">Jasper</span> Chalcedony variety colored by iron oxide

Jasper, an aggregate of microgranular quartz and/or cryptocrystalline chalcedony and other mineral phases, is an opaque, impure variety of silica, usually red, yellow, brown or green in color; and rarely blue. The common red color is due to iron(III) inclusions. Jasper breaks with a smooth surface and is used for ornamentation or as a gemstone. It can be highly polished and is used for items such as vases, seals, and snuff boxes. The specific gravity of jasper is typically 2.5 to 2.9. Jaspillite is a banded-iron-formation rock that often has distinctive bands of jasper.

<span class="mw-page-title-main">Cameo (carving)</span> Method of carving

Cameo is a method of carving an object such as an engraved gem, item of jewellery or vessel. It nearly always features a raised (positive) relief image; contrast with intaglio, which has a negative image. Originally, and still in discussing historical work, cameo only referred to works where the relief image was of a contrasting colour to the background; this was achieved by carefully carving a piece of material with a flat plane where two contrasting colours met, removing all the first colour except for the image to leave a contrasting background.

<span class="mw-page-title-main">Tiger's eye</span> Chatoyant gemstone from the quartz family

Tiger's eye is a chatoyant gemstone that is usually a metamorphic rock with a golden to red-brown colour and a silky lustre. As members of the quartz group, tiger's eye and the related blue-coloured mineral hawk's eye gain their silky, lustrous appearance from the parallel intergrowth of quartz crystals and altered amphibole fibres that have mostly turned into limonite.

<span class="mw-page-title-main">Priestly breastplate</span> Jewish ritual object worn by the High Priest

The priestly breastplate or breastpiece of judgment was a sacred breastplate worn by the High Priest of the Israelites, according to the Book of Exodus. In the biblical account, the breastplate is termed the breastplate of judgment, because the Urim and Thummim were placed upon it.(Exodus 28:30). These elements of the breastplate are said in the Exodus verse to carry the judgement of God concerning the Israelites at all times.

<span class="mw-page-title-main">Chrysoprase</span> Apple-green, gem-quality, chalcedony variety

Chrysoprase, chrysophrase or chrysoprasus is a gemstone variety of chalcedony that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. The darker varieties of chrysoprase are also referred to as prase.

<span class="mw-page-title-main">Moss agate</span>

Moss agate is a semi-precious gemstone formed from silicon dioxide. It is a form of chalcedony which includes minerals of a green color embedded in the stone, forming filaments and other patterns suggestive of moss. The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron. It is not a true form of agate, because it does not have concentric banding.

<span class="mw-page-title-main">Prasiolite</span> Mineral, quartz variety

Prasiolite is a green variety of quartz.

<span class="mw-page-title-main">Lake Superior agate</span>

The Lake Superior agate is a type of agate stained by iron and found on the shores of Lake Superior. Its wide distribution and iron-rich bands of color reflect the gemstone's geologic history in Minnesota, Wisconsin, Nebraska, Iowa, Kansas and Michigan. In 1969 the Lake Superior agate was designated by the Minnesota Legislature as the official state gemstone.

<span class="mw-page-title-main">Chrome chalcedony</span>

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<span class="mw-page-title-main">Hardstone carving</span> Artistic carving of semi-precious stones or gems

Hardstone carving is a general term in art history and archaeology for the artistic carving of predominantly semi-precious stones, such as jade, rock crystal, agate, onyx, jasper, serpentinite, or carnelian, and for an object made in this way. Normally the objects are small, and the category overlaps with both jewellery and sculpture. Hardstone carving is sometimes referred to by the Italian term pietre dure; however, pietra dura is the common term used for stone inlay work, which causes some confusion.

<span class="mw-page-title-main">Hardstone</span>

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