Opal definition

ōpəl
Frequency:
A gemstone made of this mineral, noted for its rich iridescence.
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(mineralogy) A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula SiO2·nH2O.
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(biology, genetics, biochemistry) A colloquial name used in molecular biology referring to a particular stop codon sequence, "UGA."
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A female given name from the precious stone, invented in the nineteenth century.
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(Australia) A type of petrol made by British Petroleum designed to be unable to be used for petrol sniffing.[Developed 2005.]
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A mineral of hydrated silica.
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An amorphous, iridescent mineral, SiO2n H2O, of various colors, often used as a gem; hydrous silicon oxide.
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A usually transparent mineral consisting of hydrous silica. Opal can occur in almost any color, but it is often pinkish white with a milky or pearly appearance. It typically forms within cracks in igneous rocks, in limestones, and in mineral veins. It also occurs in the silica-rich shells of certain marine organisms. Chemical formula: SiO2·nH2O.
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Other Word Forms

Noun

Singular:
opal
Plural:
opals

Origin of opal

  • Middle English opalus from Latin alteration of Greek opallios probably from Sanskrit upalaḥ from variant of upara- lower from upa below upo in Indo-European roots

    From American Heritage Dictionary of the English Language, 5th Edition

  • In Florio's A World of Words 1598 as opale, from French opale, from Latin opalus, from Byzantine Greek ὀπάλλιος (opallios), from Sanskrit उपल (upala, “gem", “stone").

    From Wiktionary