Onyx 304011 222545999 2008-06-29T22:39:13Z VMS Mosaic 638345 [[WP:UNDO|Undid]] revision 222534423 by [[Special:Contributions/76.105.173.209|76.105.173.209]] ([[User talk:76.105.173.209|talk]]) {{otheruses1|the mineral}} '''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. [[Image:Agate banded 750pix.jpg|thumb|The agate-like sardonyx (banded agate). The specimen is 2.5 cm (1 inch) wide.]] It is usually cut as a [[cabochon]], or into beads, and is also used for [[intaglio (jewellery)|intaglio]]s and [[cameo]]s, 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.<ref>[http://www.mindat.org/min-2999.html Profile of onyx]</ref> {| class="wikitable" |+Technical details |- | Chemical composition and name | SiO<SUB>2</SUB> - [[Silicon dioxide]] |- | Hardness ([[Mohs scale of mineral 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 |} ==Historical usage== [[Image:Onyks ,Australia.jpg|thumb|left|200px|Onyx from [[Australia]]]] [[Image:Onyks grudka polerowana Brazylia.jpg|thumb|left|200px|Onyx from [[Brazil]]]] ''Onyx'' is originally an [[Assyria]]n word meaning ''ring'', and so could refer to anything used for making rings. The [[Beinecke Rare Book and Manuscript Library]] at [[Yale University]] was originally planned to be coated in green onyx. However, there wasn't sufficient green onyx in the world to build such a structure, so that the designers used [[marble]]. Onyx was known to the ancient Greeks and Romans.<ref>[http://www.gemstone.org/gem-by-gem/english/onyx.html International Colored Gemstone Association: Onyx] </ref> Use of sardonyx appears in the art of [[Minoan]] [[Crete]], notably from the archaeological recoveries at [[Knossos]].<ref>[http://letmespeaktothedriver.com/site/10854/knossos.html#fieldnotes C. Michael Hogan, ''Knossos fieldnotes'', Modern Antiquarian (2007)]</ref> Onyx was used in [[Egypt]] as early as the Second Dynasty to make bowls and other pottery items.<ref>Mary Winearls Porter, ''What Rome was Built with: A Description of the Stones Employed'', 1907, H. Frowde, Rome, 108 pages</ref> In [[folk religion]], onyx is sometimes used for targets of [[curse|psychic attacks]] of all forms, especially those sexual in nature. <ref>[http://www.wiccasources.netfirms.com/magickal_properties_of_gemstones.htm The Magickal Properties of Gemstones: Black Onyx]</ref> [[Image:Black Onyx.jpg|thumb|right|150px|Black Onyx with bands of colors.]] ==Precautions== If onyx is cleaned with an [[ultrasonic]] device or cleaned with abrasive or [[ammonia]] based chemicals, discoloration of the stone may occur. ==Line note references== {{reflist}} ==See also== {{wiktionarypar|onyx}} {{Commons|Onyx}} *[[List of minerals]] {{Jewellery Materials}} {{Silica minerals}} [[Category:Quartz varieties]] [[Category:Gemstones]] [[ar:أونيكس]] [[bg:Оникс]] [[cs:Onyx]] [[de:Onyx (Mineral)]] [[es:Ónix]] [[fa:عقیق سلیمانی]] [[fr:Onyx (minéral)]] [[gl:Ónix]] [[he:אוניקס]] [[la:Onyx]] [[lv:Onikss]] [[lt:Oniksas]] [[nl:Onyx (mineraal)]] [[pl:Onyks]] [[pt:Ónix]] [[ro:Onix]] [[ru:Оникс]] [[simple:Onyx]] [[sr:Оникс]] [[fi:Onyksi]] [[sv:Onyx]]