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opal

opal

The Columbia Encyclopedia, 6th ed. | 2008 | Copyright

opal , a mineral consisting of poorly crystalline to amorphous silica, SiO 2 · n H 2 O; the water content is quite variable but usually ranges from 3% to 10%. Common opal is usually colorless or white, but it may be gray, brown, yellow, or red; the color is due to fine-grained impurities. Opal is formed at low temperatures from silica-bearing waters and can occur in fissures and cavities of any rock type. Precious, or gem, opal has a rich iridescence and remarkable play of changing colors, usually in red, green, and blue. This is the result of a specific internal structure consisting of regularly packed uniform spheres of amorphous silica a few tenths of a micron in diameter; sphere diameter and refractive index determine the range of colors displayed. The greater part of the world's supply of precious opal comes from the Coober Pedy and Andamooka fields in South Australia. The original source, known in Roman times, was in what is now E Slovakia. Precious opal has also been mined in Honduras, Mexico, and the Virgin Valley in Nevada. Fire opal is a bright red transparent or translucent opal that may or may not show a play of color.

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opal

A Dictionary of Earth Sciences | 1999 | | Copyright

opal Hydrous silica SiO2.nH2O associated with the chalcedonic (see CHALCEDONY) varieties of silica. A layer of water molecules trapped near the mineral surface causes the iridescence (opalescence) which is a diagnostic property of opal; sp. gr. 1.99–2.25; hardness 5.5–6.5; amorphous; colourless, or milky-white to grey, red, brown, blue, green, to nearly black; resinous lustre; normally massive, but can be stalactitic, botryoidal, and also in veinlets, the various varieties depending on the amount of water contained in the mineral, which can vary from 6% to 10%; no cleavage; conchoidal fracture; normally deposited at low temperatures from silica-bearing waters, and occurs as fissure fillings in rocks of any kind, and especially near geysers and hot springs. The variety known as precious opal has a milky-white or sometimes black body colour which exhibits a brilliant play of colours, usually blues, reds, and yellows. The colours can often disappear with the loss of water when the mineral is exposed to air.
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AILSA ALLABY and MICHAEL ALLABY. "opal." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

AILSA ALLABY and MICHAEL ALLABY. "opal." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O13-opal.html

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Opal

Encyclopedia of Occultism and Parapsychology | 2001 | Copyright

Opal

Gemstone of quartz or silica, praised by Pliny the Elder (ca. 23-79 C.E.), who wrote: "For in them you shall see the living fire of the ruby, the glorious purple of the amethyst, the green sea of the emerald, all glittering together in an incredible mixture of light." In ancient times many legends existed around its claimed virtues. It was believed to recreate the heart, ward off airborne contagions, and dispel sadness. It was also good for weak eyes. The name poederos, applied to the opal, refers to the complexion of youth.

The superstition that opals were unlucky seems to have been popularized by Sir Walter Scott's novel Anne of Geirstein (1829). The story claims the opal worn by Baroness Hermione of Arnheim lost its luster after a drop of water touched it.
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opal

The Oxford Dictionary of Phrase and Fable | 2006 | | Copyright

opal a gemstone which is typically semi-transparent and showing many small points of shifting colour against a pale or dark ground; it is often referred to allusively to evoke the idea of changing colours.

The belief that opals are unlucky is recorded from the 19th century, and may originate with Walter Scott's novel Anne of Geierstein (1829), in which an opal brings ill fortune on its owner.
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ELIZABETH KNOWLES. "opal." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

ELIZABETH KNOWLES. "opal." The Oxford Dictionary of Phrase and Fable. 2006. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O214-opal.html

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opal

The Oxford Pocket Dictionary of Current English | 2009 | Copyright

o·pal / ˈōpəl/ • n. a gemstone consisting of hydrated silica, typically semitransparent and showing varying colors against a pale or dark ground. ORIGIN: late 16th cent.: from French opale or Latin opalus, probably based on Sanskrit upala ‘precious stone’ (having been first brought from India).

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Opal

A Dictionary of First Names | 2006 | | Copyright

Opal ♀ One of the rarer girls' names created in the late 19th century from vocabulary words for gemstones. This English word is ultimately derived (via Latin and Greek) from an Indian language (compare Sanskrit upala ‘precious stone’).
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PATRICK HANKS, KATE HARDCASTLE, and FLAVIA HODGES. "Opal." A Dictionary of First Names. 2006. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

PATRICK HANKS, KATE HARDCASTLE, and FLAVIA HODGES. "Opal." A Dictionary of First Names. 2006. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O41-Opal.html

PATRICK HANKS, KATE HARDCASTLE, and FLAVIA HODGES. "Opal." A Dictionary of First Names. 2006. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O41-Opal.html

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opal

World Encyclopedia | 2005 | Copyright

opal Non-crystalline variety of quartz, found in recent volcanoes, deposits from hot springs and sediments. Usually colourless or white with a rainbow play of colour in gem forms, it is the most valuable of quartz gems. Hardness 5.5–6.5; r.d. 2.0.
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opal

The Concise Oxford Dictionary of English Etymology | 1996 | | Copyright

opal XVI. — F. opale or L. opalus, prob. ult. (like late Gr. opállios) — Skr. úpala- stone.
Hence opalescent XIX.
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T. F. HOAD. "opal." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

T. F. HOAD. "opal." The Concise Oxford Dictionary of English Etymology. 1996. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O27-opal.html

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opal

Oxford Dictionary of Rhymes | 2007 | Copyright

opal •apple, chapel, chappal, Chappell, dapple, grapple, scrapple •scalpel •ample, trample •pineapple •carpal, carpel •example, sample •sepal •stemple, temple •maple, papal, staple •peepul, people, steeple •tradespeople • sportspeople •townspeople • workpeople •cripple, fipple, nipple, ripple, stipple, tipple, triple •dimple, pimple, simple, wimple •Oedipal • maniple • manciple •municipal •principal, principle •participle • multiple •archetypal, disciple, typal •prototypal •hopple, popple, stopple, topple •gospel •Constantinople, copal, nopal, opal, Opel •duple, pupal, pupil, scruple •quadruple • septuple • sextuple •quintuple • octuple •couple, supple •crumple, rumple, scrumple •syncopal • episcopal • purple

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Aqua blue Peruvian opal sterling silver necklace. (Image by Natalia Photos, CC)

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