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Opal

Opal is a hydrated amorphous form of silica (SiO2·nH2O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to the amorphous (chemical) physical structure, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals. It is deposited at a relatively low temperature and may…

History, Precious opal & Local atomic structure

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Absorption spectra
green stones: 660 nm, 470 nm cutoff
Birefringence
none
Category
Mineraloid
Cleavage
None
Color
Colorless, white, yellow, red, orange, green, brown, black, blue, pink
Crystal habit
Irregular veins, in masses, in nodules

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Overview

Precious opal

Common opal

Varieties of common opal

History

Sources

Fossil opal

Synthetic opal

Local atomic structure

Etymology

Historical superstitions

Examples

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Map overview Semantic statistics

Opal

Nodes157
Edges156
Triples279
Avg. degree1.99
Density0.012739
Components1

How this topic connects Entity context

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Opal

Top relations

related to Examples · 26
Opal → Andamooka, Australia, Beauharnais, Beverly, Bug, Coober PedyThe Andamooka Opal, Earth, Fire, Flame Queen OpalOpal, France, Grand Central Terminal, Guinness Book, Joséphine, Napoleon, New York City, Queen Elizabeth II, Queen's OpalThe Addyman, RecordsThe Rainbow Virgin, Roebling Opal, Smithsonian InstitutionThe Galaxy Opal
related to External links · 20
Opal → December, Farlang, February, Fields, Fossils, Georg Agricola, Hist, ICA's Opal Page, International Colored Stone AssociationOpal, Isaac Newton, Map, Mineralogy DatabaseOpalworld Archived, October, Opal Mineral, References Archived, South Australian Museum Archived, Theophrastus, Wayback Machine Accessed, Wayback Machine Australian Opal, Wayback Machine Localities
related to Historical superstitions · 18
Opal → April, Arnheim, As, Baroness, Due, Europe, Even, Following, Geierstein, In, In Scott's, It, Middle Ages, Russian, Scott's, Sir Walter Scott's Anne, When, Within
related to Other locations · 18
Opal → Another, Brazil, Canada, Czech Republic, Erandique, Guatemala, Honduras, Hungary, Idaho, Indonesia, Nicaragua, Other, Pedro II, Piauí, Slovakia, Spencer, Turkey, United States
related to Virgin Valley, Nevada · 18
Opal → Black Peacock, Bonanza, Humboldt County, Miocene-age, Most, Nevada, Opal Queen, Opals, Rainbow Ridge, Rainbow Ridge Mine, Roebling, Royal Peacock, Smithsonian Institution, Some, The, The Virgin Valley, Virgin Valley, WRT Stonetree/Black Beauty
related to Ethiopia · 17
Opal → Australia, Brazil, Ethiopia, Ethiopia's Wollo Province, Ethiopian, In, Menz Gishe District, North Shewa Province, Shewa Province, The, The Wollo Province, These, This Shewa Province, Wegeltena, Wello, Welo, Wollo Province
related to Mexico · 16
Opal → Although, Another, Cantera, Colón, During, Ezequiel Montes, Fire, In, Mexican, Mexico, Querétaro, Tequisquiapan, The, This, Today's, US
related to Sources · 14
Opal → Australia, Australian, Because, Ethiopia, Ethiopian, In, Laurs, Mesfin, South Australia, The, United States Geological Survey, USGS, Wegeltena, Yet
related to Varieties of common opal · 14
Opal → Blue, Girasol, However, Idaho, It, Madagascar, Mexico, Nevada, Oregon, Owyhee, Peru, Peruvian, The, Virgin Valley
related to Etymology · 11
Opal → As, Elder, Latin, Opalia, Ops, Pliny, Roman, Sanskrit, Saturn, Saturnalia, The

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Important terminology

opals precious also silica color black water may common found australia light form play fire amorphous structure often white around

Entity relationships Subject–Predicate–Object triples

SubjectPredicateObjectConfidenceSrc
OpalAbsorption spectragreen stones: 660 nm, 470 nm cutoff1.00infobox
OpalBirefringencenone1.00infobox
OpalCategoryMineraloid1.00infobox
OpalCleavageNone1.00infobox
OpalColorColorless, white, yellow, red, orange, green, brown, black, blue, pink1.00infobox
OpalCrystal habitIrregular veins, in masses, in nodules1.00infobox
OpalCrystal systemAmorphous1.00infobox
OpalDensity2.09 g/cm31.00infobox
OpalDiagnostic featuresdarkening upon heating1.00infobox
OpalDiaphaneityopaque, translucent, transparent1.00infobox
OpalFormulaHydrated silica. SiO2·nH2O1.00infobox
OpalFractureConchoidal to uneven1.00infobox
OpalIMA symbolOpl1.00infobox
OpalLusterSubvitreous to waxy1.00infobox
OpalMohs scale hardness5.5–61.00infobox
OpalOptical propertiesSingle refractive, often anomalous double refractive due to strain1.00infobox
OpalPleochroismNone1.00infobox
OpalPolish lusterVitreous to resinous1.00infobox
OpalRefractive index1.450+0.020 −0.080 Mexican opal may read as low as 1.37, but typically reads 1.42–1.431.00infobox
OpalSolubilityhot salt water, bases, methanol, humic acid, hydrofluoric acid1.00infobox
OpalSpecific gravity2.15+0.08 −0.901.00infobox
OpalStreakWhite1.00infobox
OpalUltraviolet fluorescenceblack or white body color: inert to white to moderate light blue, green, or yellow in long and short wave, may also phosphoresce, common opal: inert to strong green or yellowish…1.00infobox
Opalcausesit to diffract light0.90text
Opalis ahydrated amorphous form of silica0.90text
Opalis atype of hyalite opal that exhibits a bluish glow or sheen that follows the light source around0.90text
Opalis anational gemstone of Australia0.90text
Opalis aofficial gemstone of Nevada0.90text
Opalis atransparent to translucent opal with warm body colors of yellow to orange to red0.90text

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