Onyx
Onyx | ||
---|---|---|
Specific gravity 2.55–2.70 | | |
Optical properties | Uniaxial/+ | |
Refractive index | 1.530–1.543 | |
References | [1][2] |
Onyx is the parallel-banded variety of chalcedony, an oxide mineral. Agate and onyx are both varieties of layered chalcedony that differ only in the form of the bands; agate has curved bands while onyx has parallel bands. The colors of its bands range from black to almost every color. Specimens of onyx commonly contain bands of black and/or white.[1] 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".[1][3][4]
Etymology
Onyx comes through Latin (of the same spelling), from the Ancient Greek ὄνυξ, meaning "claw" or "fingernail". Onyx with pink and white bands can sometimes resemble a fingernail.[5] The English word "nail" is cognate with the Greek word.
Varieties
Onyx is formed of bands of
Sardonyx is a variant in which the colored bands are
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.[9][10]
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.[11] 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.[8][12] These techniques are still used, as well as other dyeing treatments, and most so-called "black onyx" sold is artificially treated.[13] In addition to dye treatments, heating and treatment with nitric acid have been used to lighten or eliminate undesirable colours.[8]
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.[9]
Historical use
It has a long history of use for
Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.[16] Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.[17]
Brazilian green onyx was often used as plinths for
Onyx is mentioned in the Bible many times.[20] Sardonyx (onyx in which white layers alternate with sard - a brownish color) is mentioned in the Bible as well.[21]
Onyx was known to the Ancient Greeks and Romans.[22] The first-century naturalist Pliny the Elder described both type of onyx and various artificial treatment techniques in his Naturalis Historia.[11]
Slabs of onyx (from the
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.
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.
Superstitions
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.[25] A traditional Persian belief is that it helped with epilepsy.[26] Sardonyx was traditionally used by English midwives to ease childbirth by laying it between the breasts of the mother.[27]
See also
- Birthstone – Gemstones representing a person's birth month
- Chalcedony – Microcrystalline varieties of silica
- Gemstone – Piece of mineral crystal used to make jewelry
- Jasper – Chalcedony variety colored by iron oxide
- List of minerals – List of minerals with Wikipedia articles
References
- ^ a b c Onyx, Mindat.org, retrieved 2015-08-22
- ^ "Onyx". gemdat.org. Retrieved 2015-08-22.
- ISBN 9783662042885.
- ISBN 9781402768293.
- ^ "Online Etymology Dictionary". etymonline.com. Retrieved 22 August 2015.
- ISBN 3-540-40882-7.
- ^ Sinkankas, John (1959). Gemstones of North America. Vol. 1. Princeton, New Jersey: Van Nostrand. p. 316.
- ^ a b c "The Manufacture of Gem Stones". Scientific American. New York: Munn & Company: 49. 25 July 1874.
- ^ a b "Onyx". mindat.org. Retrieved 22 August 2015.
- ISBN 0-471-15677-9.
- ^ ISBN 0-7506-3173-2.
- ISBN 0-7506-4411-7.
- ISBN 0-87311-012-9.
- ^ Kraus, Edward Henry; Slawson, Chester Baker (1947). Gems and Gem Materials. New York, New York: McGraw-Hill. p. 227.
- ^ Liddicoat, Richard Thomas; Copeland, Lawrence L. (1974). The Jewelers' Manual. Los Angeles, California: Gemological Institute of America. p. 87.
- ^ Porter, Mary Winearls (1907). What Rome was Built with: A Description of the Stones Employed. Rome: H. Frowde. p. 108.
- ^ C. Michael Hogan (2007) Knossos fieldnotes, The Modern Antiquarian
- ^ "Ferdinand Preiss". Hickmet.com. Retrieved 18 June 2015.
- ^ "Lot 419, Schmidt-Hofer, Otto, 1873-1925 (Germany)". ArtValue.com.
- ^ "BibleGateway". biblegateway.com. Retrieved 22 August 2015.
- ^ "BibleGateway". biblegateway.com. Retrieved 22 August 2015.
- ^ Administrator. "Onyx". gemstone.org. Retrieved 22 August 2015.
- ^ "The Interiors". Villa Tugendhat. Retrieved 2 September 2017.
- ^ "Tugendhat Villa in Brno". UNESCO. Retrieved 2 September 2017.
- ^ Firefly Guide to Gems By Cally Oldershaw, p.168
- ^ The Mining World, Volume 32, June 25, 1910, p.1267
- ^ Three thousand years of mental healing By George Barton Cutten, 1911 P.202
External links
- Rudler, Frederick William (1911). Encyclopædia Britannica. Vol. 20 (11th ed.). p. 118. .