''opal'' ▫ᴱᴺ｜Definition｜1st｜20260813235252-00-⌔

opal - Wiktionary, the free dictionary

English

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Noun

opal (plural opals)

• (mineralogy) A mineral consisting, like quartz, of silica, but inferior to quartz in hardness and specific gravity, of the chemical formula Si O${}_2$ · n H${}_2$ O.
  • (gemology) A precious gem, an iridescent gemstone found in the opal-silica mineral substrate (potch)
  • ✤ Although there are dozens of different types of gems, among the best known and most important are […]. (Common gem materials not addressed in this article include amber, amethyst, chalcedony, garnet, lazurite, malachite, opals, peridot, rhodonite, spinel, tourmaline, turquoise and zircon.)¹
• The colour of opal: any shade of blue with bright flecks of other colours, such as white, yellow, and red.
  • ✤ The witchery of the dawn turned the grey river-reaches to purple, gold, and opal; and it was as though the lumbering dhoni crept across the splendors of a new heaven.²
• (biology, genetics, biochemistry) A colloquial name used in molecular biology referring to a particular stop codon sequence, “UGA.”
• Any of various lycaenid butterflies of the genus Nesolycaena.

Etymology

In Florio ’s A World of Words 1598 as opale, from French opale, from Latin opalus, from Byzantine Greek ὀπάλλιος (opállios), from Sanskrit उपल (upala, “gem, stone”), from उपरि (upári, “the upper millstone”).³ Distantly related to over.

Pronunciation

• (UK) IPA: /ˈəʊpəl/
• Audio (Southern England): 🔊
• (US) IPA: /ˈoʊpəl/
• Rhymes: -əʊpəl

Printed 2026-08-13.

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Footnotes

1. 2012 March, Lee A. Groat, “Gemstones”, in American Scientist ‎${}^{[2]}$, volume 100, number 2, archived from the original on 14 June 2012, page 128: ↩

2. 1889, Rudyard Kipling, “Only A Subaltern”, in Under the Deodars, Boston: The Greenock Press, published 1899, page 141: ↩

3. Chambers Dictionary of Etymology, Robert K. Barnhart (ed.), Chambers, 1988 ↩