onyx

[Middle English onix, from Old French, from Latin onyx, from Greek onux, nail, onyx.]

For more information on onyx, visit Britannica.com.

Banded chalcedonic quartz, in which the bands are straight and parallel, rather than curved, as in agate. Unfortunately, in the colored-stone trade, gray chalcedony dyed in various solid colors such as black, blue, and green is called onyx, with the color used as a prefix. Because the color is permanent, the fact that it is the result of dyeing is seldom mentioned.

The natural colors of true onyx are usually red or brown with white, although black is occasionally encountered as one of the colors. When the colors are red-brown with white or black, the material is known as sardonyx; this is the only kind commonly used as a gemstone. Its most familiar gem use is in cameos and intaglios. See also Cameo; Chalcedony.

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adjective

Of the darkest achromatic visual value: black, ebon, ebony, inky, jet¹, jetty, pitch-black, pitchy, sable, sooty. See colors/colorless.

A banded, varicolored form of quartz, closely related to agate; cut into slabs, polished, and used for decorative building stone.

This article is about the mineral. For other uses, see Onyx (disambiguation).

the Gemma Augustea, a Roman cameo engraved gem, 9-12 AD, in two layered onyx; 19 × 23 cm.

Sardonyx (banded agate). The specimen is 2.5 cm (1 inch) wide.

Onyx is a cryptocrystalline form of quartz. The colors of its bands range from white to almost every color (save some shades, such as purple or blue). Commonly, specimens of onyx available contain bands of colors of white, tan, and brown. Sardonyx is a variant in which the colored bands are sard (shades of red) rather than black. Pure black onyx is common, and perhaps the most famous variety, but not as common as onyx with banded colors.

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

The name has sometimes been used, incorrectly, to label other banded lapidary materials, such as banded calcite found in Mexico, Pakistan, 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]

Technical details

Chemical composition and name	SiO2 - Silicon dioxide
Hardness (Mohs scale)	7
Specific gravity	2.65 - 2.667
Refractive index (R.I.)	1.543 - 1.552 to 1.545 - 1.554
Birefringence	0.009
Optic sign	Positive
Optical character	Uniaxial

Contents 1 Etymology 2 Historical usage 3 References 4 See also

Etymology

Onyx comes through Latin from the Greek onyx meaning 'claw' or 'fingernail'. With its fleshtone color, onyx can be said to resemble a fingernail. The English word 'nail' is cognate with the Greek word.^[2]

Historical usage

Onyx from Australia.

Onyx from Brazil.

Onyx was known to the ancient Greeks and Romans.^[3] Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.^[4] Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.^[5]

Black onyx with bands of colors.

References

1. ^ Profile of onyx
2. ^ http://www.etymonline.com/index.php?term=onyx
3. ^ International Colored Gemstone Association: Onyx
4. ^ C. Michael Hogan (2007) Knossos fieldnotes, The Modern Antiquarian
5. ^ Mary Winearls Porter, What Rome was Built with: A Description of the Stones Employed, 1907, H. Frowde, Rome, 108 pages

See also

Look up onyx in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: Onyx

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Dansk (Danish)
n. - onyks

Nederlands (Dutch)
onyx, steensoort

Français (French)
n. - onyx

Deutsch (German)
n. - Onyx

Ελληνική (Greek)
n. - (ορυκτολ.) όνυχας

Italiano (Italian)
onice

Português (Portuguese)
n. - ônix (m)

Русский (Russian)
оникс

Español (Spanish)
n. - ónice, ónix

Svenska (Swedish)
n. - onyx

中文（简体）(Chinese (Simplified))
缟玛瑙

中文（繁體）(Chinese (Traditional))
n. - 縞瑪瑙

한국어 (Korean)
n. - (줄무늬가 있는)마노, 손,발톱

日本語 (Japanese)
n. - 縞瑪瑙, オニキス, 縞大理石
adj. - 漆黒の

العربيه (Arabic)
‏(الاسم) العقيق اليماني‏

עברית (Hebrew)
n. - ‮שוהם, קוורץ צבעוני, אנך‬

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