iridescent semi-precious stone of hydrated silica
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Opal Definition from Language, Idioms & Slang Dictionaries & Glossaries
(n.)
A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity.
Webster's Revised Unabridged Dictionary (1913), edited by Noah Porter. AboutA mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity.
opal
\o"pal\ (?), n. [l. opalus: cf. gr. &?;, skr. upala a rock, stone, precious stone: cf. f. opale.] (min.) a mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity.
note: the precious opal presents a peculiar play of colors of delicate tints, and is highly esteemed as a gem. one kind, with a varied play of color in a reddish ground, is called the harlequin opal. the fire opal has colors like the red and yellow of flame. common opal has a milky appearance. menilite is a brown impure variety, occurring in concretions at menilmontant, near paris. other varieties are cacholong, girasol, hyalite, and geyserite.
similar words(4)
jasper opal
harlequin opal
wood opal
fire opal
Noun
1. a translucent mineral consisting of hydrated silica of variable color; some varieties are used as gemstones
(hypernym) mineral
(hyponym) black opal
(derivation) opalize, opalise
Opal Definition from Government Dictionaries & Glossaries
Opal Definition from Science & Technology Dictionaries & Glossaries
General Information:
SiO2·n(H2O)
(Molecular Weight = 87.11 gm)
Silicon 32.24 % Si
Hydrogen 3.47 % H
Oxygen 64.29 % O
SiO21.5(H2O)
Sedimentary and secondary from the alteration of high silica igneous extrusive rocks.
World wide occurrences.
From the Old Indian upala - "precious stone."
Physical Properties:
None
white, yellow, red, brown, or blue.
1.9 - 2.3, Average = 2.09
Transparent to translucent to opaque
Amorphous - No crystalline form or imitative shape., Massive - Uniformly indistinguishable crystals forming large masses., Reniform - "Kidney like" in shape (e.g.. hematite).
5.5-6 - Knife Blade-Orthoclase
Fluorescent, Short UV=greenish yellow, Long UV=white.
Vitreous - Dull
white
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SiO2 n(H2O)
Opal Definition from Encyclopedia Dictionaries & Glossaries
Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most commonly found with limonite, sandstone, rhyolite, marl and basalt. Opal is the national gemstone of Australia, which produces 97% of the world's supply.
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OPAL (Open Pool Australian Lightwater reactor) is a 20 megawatt (MW) pool-type nuclear research reactor that was officially opened on 20 April 2007 at the Australian Nuclear Science and Technology Organisation (ANSTO) Research Establishment at Lucas Heights, located in South Sydney, Australia.
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