Onyx
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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>Template:Cite book</ref><ref>Template:Cite book</ref>
EtymologyEdit
Onyx comes through Latin (of the same spelling), from the Ancient Greek {{#invoke:Lang|lang}} (Template:Transliteration), meaning Template:Gloss or Template:Gloss. Onyx with pink and white bands can sometimes resemble a fingernail.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The English word "nail" is cognate with the Greek word.
VarietiesEdit
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>Template:Cite book</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. 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>Template:Cite book</ref><ref name="SA July 1874">Template:Cite journal</ref>Template:Better source neededTemplate:Disputed inline
Imitations and treatmentsEdit
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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite book</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">Template:Cite book</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>Template:Cite book</ref> These techniques are still used, as well as other dyeing treatments, and most so-called "black onyx" sold is artificially treated.<ref>Template:Cite book</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 occurrenceEdit
Onyx can be 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.<ref name=Mindat/>
Historical useEdit
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>Template:Cite book</ref> Some onyx is natural but much of the material in commerce is produced by the staining of agate.<ref>Template:Cite book</ref>
Onyx was used in Egypt as early as the Second Dynasty to make bowls and other pottery items.<ref>Template:Cite book</ref> Use of sardonyx appears in the art of Minoan Crete, notably from the archaeological recoveries at Knossos.<ref>C. Michael Hogan (2007) 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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Green onyx was also used for trays and pin dishes – produced mainly in Austria – often with small bronze animals or figures attached.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Onyx is mentioned in the Bible many times.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Sardonyx (onyx in which white layers alternate with sard – a brownish color) is mentioned in the Bible as well.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Onyx was known to the Ancient Greeks and Romans.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</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>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
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.Template:Citation needed
SuperstitionsEdit
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.<ref>Firefly Guide to Gems By Cally Oldershaw, p.168</ref> A traditional Persian belief 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 alsoEdit
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ReferencesEdit
External linksEdit
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