{{Short description|Black and white variety of agate}} {{About|the mineral|the New York hip hop group|Onyx (hip hop group)|other uses}} {{Infobox mineral |boxtextcolor=#FFFFFF|boxbgcolor=#353935| name = Onyx | category = Tectosilicate minerals | group = Quartz group | IMAstatus = Variety of quartz (chalcedony) | image = Agate-Quartz-49959.jpg | alt = Black onyx with concentric white bands | caption = Onyx with concentric banding | formula = SiO<sub>2</sub> (silicon dioxide) | molweight = 60.08 g/mol | color = Black and white; red to brown with black or white (sardonyx) | system = Trigonal (quartz), Monoclinic (moganite) | cleavage = None | fracture = Uneven, conchoidal | mohs = 6.5–7 | luster = Vitreous, silky | streak = White | gravity = 2.55–2.70 | diaphaneity = Translucent | opticalprop = Uniaxial/+ | refractive = 1.530–1.543 | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | references = <ref name=mindat>{{Mindat |id=2999 |name=Onyx |access-date=2025-02-14}}</ref><ref>{{cite web |url=https://gemdat.org/gem-2999.html |title=Onyx |publisher=gemdat.org |access-date=2015-08-22}}</ref> }}
'''Onyx''' is a typically black-and-white banded variety of agate, a silicate mineral. The bands can also be monochromatic with alternating light and dark bands. ''Sardonyx'' is a variety with red to brown bands alternated with black or white bands. The name "onyx" is also frequently used for level-banded (parallel-banded) agates, but in proper usage it refers to color pattern not band structure.<ref name=mindat/> Onyx, as a descriptive term, has also been incorrectly 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".<ref name=mindat/><ref>{{cite book |last=Manutchehr-Danai|first=Mohsen |year=2013 |title=Dictionary of Gems and Gemology |location=New York |publisher=Springer |pages=340–341 |isbn=9783662042885}}</ref><ref>{{cite book |last=Schumann|first=Walter |year=2009 |title=Gemstones of the World |location=New York |publisher=Sterling |page=158 |isbn=9781402768293}}</ref>
==Etymology== ''Onyx'' comes through Latin (of the same spelling), from the Ancient Greek {{lang|grc|ὄνυξ}} ({{Transliteration|grc|onyx}}), meaning {{gloss|claw}} or {{gloss|fingernail}}. Onyx with pink and white bands can sometimes resemble a fingernail.<ref>{{cite web|url=http://www.etymonline.com/index.php?term=onyx|title=Online Etymology Dictionary|work=etymonline.com|access-date=22 August 2015}}</ref> The English word "nail" is cognate with the Greek word.
==Varieties== [[File:Red onyx - Handicraft.jpg|thumb|Cabochons of red onyx, also called sardonyx]] thumb|left|alt=A photograph of 6 smooth black pebbles with white markings, arranged in a circle|Black onyx with white streaks
Onyx is formed of chalcedony bands in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel, unlike the more chaotic banding that often occurs in agates.<ref>{{cite book |last1=Assaad|first1=Fakhry A. |last2=LaMoreaux|first2=Philip E. Sr. |title=Field Methods for Geologists and Hydrogeologists |year=2004 |publisher=Springer-Verlag |location=Berlin, Heidelberg, New York |isbn=3-540-40882-7 |editor-last=Hughes|editor-first=Travis H. |page=8}}</ref>
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 it is not as common as onyx with colored bands. Several artificial treatments have been used since ancient times to produce the black color in "black onyx" and the reds and yellows in sardonyx. Most "black onyx" on the market is artificially colored.<ref>{{cite book |last=Sinkankas|first=John |title=Gemstones of North America |year=1959 |publisher=Van Nostrand |location=Princeton, New Jersey |page=316 |volume=1}}</ref><ref name="SA July 1874">{{cite journal |title=The Manufacture of Gem Stones |journal=Scientific American |date=25 July 1874 |page=49 |publisher=Munn & Company |location=New York}}</ref>
==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 more readily available. The majority of carved items sold as "onyx" today are this carbonate material.<ref name=Mindat>{{cite web |url=http://www.mindat.org/min-2999.html |title=Onyx |publisher=mindat.org |access-date=22 August 2015}}</ref><ref>{{cite book|last1=Hurlbut|first1=Cornelius S.|last2=Sharp|first2=W. Edwin|title=Dana's Minerals and How to Study Them|year=1998|publisher=Wiley|location=New York, New York|isbn=0-471-15677-9|page=[https://archive.org/details/danasmineralshow00hurl/page/200 200]|edition=4th|url-access=registration|url=https://archive.org/details/danasmineralshow00hurl/page/200}}</ref>
Artificial onyx types have also been produced from common chalcedony and plain agates. The first-century naturalist Pliny the Elder described these techniques used in Roman times.<ref name="O'Donoghue">{{cite book|last=O'Donoghue|first=Michael|title=Synthetic, Imitation, and Treated Gemstones |year=1997 |publisher=Butterworth-Heinemann |location=Boston |isbn=0-7506-3173-2|pages=125–127}}</ref> Treatments for producing black and other colors include soaking or boiling chalcedony in sugar solutions, then treating with sulfuric or hydrochloric acid to carbonize sugars which had been absorbed into the top layers of the stone.<ref name="SA July 1874"/><ref>{{cite book|last=Read|first=Peter G.|title=Gemmology|year=1999|publisher=Butterworth-Heinemann|location=Oxford |isbn=0-7506-4411-7|page=160}}</ref> These techniques are still used, as well as other dyeing treatments, and most so-called "black onyx" sold is artificially treated.<ref>{{cite book|last=Liddicoat|first=Richard Thomas|title=Handbook of Gem Identification |year=1987|publisher=Gemological Institute of America|location=Santa Monica, California |isbn=0-87311-012-9 |pages=158–160 |edition=12th}}</ref> In addition to dye treatments, heating and treatment with nitric acid have been used to lighten or eliminate undesirable colors.<ref name="SA July 1874"/>
==Geographic occurrence== Onyx can be found in various regions of the world, including Mexico, Greece, Yemen, Uruguay, Argentina, Australia, Brazil, Canada, China, Czech Republic, Germany, Pakistan, India, Indonesia, Madagascar, the UK, and various states in the US.<ref name=Mindat/>
==Historical use== [[File:Kunsthistorisches Museum Vienna June 2006 031.jpg|thumb|alt=A photograph showing a roughly rectangular gem set in a gold frame with 2 carved panels with various figures carved in shallow from translucent white chalcedony against a solid black background|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.<ref>{{cite book|last1=Kraus|first1=Edward Henry|last2=Slawson|first2=Chester Baker|title=Gems and Gem Materials|url=https://archive.org/details/in.ernet.dli.2015.280103|year=1947|publisher=McGraw-Hill|location=New York, New York|page=[https://archive.org/details/in.ernet.dli.2015.280103/page/n234 227]}}</ref> Some onyx is natural but much of the material in commerce is produced by the staining of agate.<ref>{{cite book|last1=Liddicoat|first1=Richard Thomas|last2=Copeland|first2=Lawrence L.|title=The Jewelers' Manual|year=1974|publisher=Gemological Institute of America|location=Los Angeles, California|page=87}}</ref>
Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.<ref>{{cite book|last=Porter|first=Mary Winearls|author-link=Mary Winearls Porter|title=What Rome was Built with: A Description of the Stones Employed|url=https://archive.org/details/whatromewasbuilt00portiala|year=1907|publisher=H. Frowde|location=Rome|page=[https://archive.org/details/whatromewasbuilt00portiala/page/108 108]}}</ref> Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.<ref>C. Michael Hogan (2007) [http://www.themodernantiquarian.com/site/10854/knossos.html#fieldnotes ''Knossos fieldnotes'', The Modern Antiquarian]</ref>
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.<ref name=Hickmet>{{cite web|title=Ferdinand Preiss|url=http://www.hickmet.com/artist/fritz-ferdinand-preiss|website=Hickmet.com|access-date=18 June 2015}}</ref> Green onyx was also used for trays and pin dishes—produced mainly in Austria—often with small bronze animals or figures attached.<ref>{{cite web|title=Lot 419, Schmidt-Hofer, Otto, 1873–1925 (Germany)|website=ArtValue.com|url=http://www.artvalue.com/auctionresult--schmidt-hofer-otto-1873-1925-g-art-deco-skulptur-in-form-eine-2160708.htm|access-date=2016-02-04|archive-date=2018-11-19|archive-url=https://web.archive.org/web/20181119223749/http://www.artvalue.com/auctionresult--schmidt-hofer-otto-1873-1925-g-art-deco-skulptur-in-form-eine-2160708.htm|url-status=dead}}</ref>
Onyx is mentioned in the Bible many times.<ref>{{cite web|url=https://www.biblegateway.com/quicksearch/?quicksearch=Onyx&version=DRA&resultspp=25|title=BibleGateway|work=biblegateway.com|access-date=22 August 2015}}</ref> Sardonyx (onyx in which white layers alternate with sard—a brownish color) is mentioned in the Bible as well.<ref>{{cite web|url=https://www.biblegateway.com/quicksearch/?quicksearch=sardOnyx&qs_version=DRA|title=BibleGateway|work=biblegateway.com|access-date=22 August 2015}}</ref>
Onyx was known to the ancient Greeks and Romans.<ref>{{cite web|url=http://www.gemstone.org/gem-by-gem/english/onyx.html|title=Onyx|author=Administrator|work=gemstone.org|access-date=22 August 2015|archive-date=17 April 2008|archive-url=https://web.archive.org/web/20080417034940/http://www.gemstone.org/gem-by-gem/english/onyx.html|url-status=dead}}</ref> The first-century naturalist Pliny the Elder described both types of onyx and various artificial treatment techniques in his ''Naturalis Historia''.<ref name="O'Donoghue"/>
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.<ref>{{cite web|title=The Interiors|url=http://www.tugendhat.eu|publisher=Villa Tugendhat|access-date=2 September 2017}}</ref><ref>{{cite web|title=Tugendhat Villa in Brno|url=https://whc.unesco.org/en/list/1052|publisher=UNESCO|access-date=2 September 2017}}</ref>
===Culture=== The ancient Romans entered battle carrying amulets of sardonyx engraved with Mars, the god of war. This was assumed to bestow courage in battle. In Renaissance Europe, wearing sardonyx was assumed to bestow eloquence.<ref>Firefly Guide to Gems By Cally Oldershaw, p.168</ref> A traditional Persian assumption is that it helped with epilepsy.<ref>The Mining World, Volume 32, June 25, 1910, p.1267</ref> Sardonyx was traditionally used by English midwives to ease childbirth by laying it between the breasts of the mother.<ref>Three thousand years of mental healing By George Barton Cutten, 1911 P.202</ref>
==See also== {{Portal|Minerals}} * {{Annotated link|List of minerals}} * {{Annotated link|Chalcedony}} * {{Annotated link|Gemstone}} * {{Annotated link|Jasper}} * {{Annotated link|Birthstone}}
==References== {{Reflist}}
==External links== {{Commons}} {{Wiktionary|onyx}} * {{cite EB1911|first=Frederick William |last=Rudler |wstitle=Onyx |volume=20 |page=118 |short=x}}
{{Jewellery}} {{Silica minerals}} {{Shades of black}} {{Authority control}}
Category:Chalcedony Category:Quartz gemstones