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• opal
  opal

  noun

  a mineral, an amorphous form of silica, SiO 2 with some water of hydration, found in many varieties and colors, including a form that is milky white.
• Opal
  Opal

  noun

  a female given name.

opal

¹ American  

[oh-puhl] / ˈoʊ pəl /

noun

• opals
  plural

1. a mineral, an amorphous form of silica, SiO 2 with some water of hydration, found in many varieties and colors, including a form that is milky white.

2. an iridescent variety of this that is used as a gem.

3. a gem of this.

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Opal ² American  

[oh-puhl] / ˈoʊ pəl /

noun

1. a female given name.

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opal British  

/ ˈəʊpəl /

noun

1. an amorphous, usually iridescent, mineral that can be of almost any colour, found in igneous rocks and around hot springs. It is used as a gemstone. Composition: hydrated silica. Formula: SiO 2 . n H 2 O

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opal Scientific  

/ ō′pəl /

1. 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: SiO ₂ ·nH ₂ O.

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Usage

What does opal mean? An opal is a gemstone that’s best known for its iridescent, milky-white variety. Other varieties are black and gray, but it can be almost any color. As a mineral, opal is a form of silica. Unlike many of the other gemstones used in jewelry, opal is not crystalline, meaning it does not form in a crystal structure—it looks like a stone, as opposed to a faceted jewel like a diamond. Opal gemstones are classified as common or precious. Precious is a label given to certain gemstones that are high in value. Opals labeled precious are typically those that display a high level of iridescence. Opal is the traditional birthstone for the month of October. It is associated with the zodiac signs Libra and Scorpio. Example: The opal pendant had flecks of green, pink, and blue.

Other Word Forms

Derived Forms

• opal-like
  adjective

Inflected Forms

Nouns

• opals
  plural

Etymology

Origin of opal

1350–1400; Middle English < Latin opalus < Greek opállios opal, gem; probably from a source akin to Sanskrit upala precious stone

Explanation

An opal is a gem, a semi-precious stone that comes in many shimmery, partly translucent colors. If your birthday is in October, an opal is your birthstone. An opal is a mineral made of silica, and it's found within the cracks and notches of many different kinds of rock. Most of the world's supply of opals comes from Australia. A polished opal that's been set in a ring or necklace is usually several shades or colors — most often blues and greens — with sparkles or shimmers decorating the stone. The word opal comes from the Latin opalus, and its ultimate root is probably the Sanskrit upala, "precious stone."

Example Sentences

See Examples For:

opal Opal opals

The broth is still at the center of all things La Mer: Past celebrations have involved “broth-tinis,” which are just cocktails made to resemble the opal liquid with its root beer smell.

From The Wall Street Journal ● Mar. 18, 2026

All opal fossils are rare - monotreme ones even more so - but these specimens are "a revelation", says Ms Smith.

From BBC ● May 27, 2024

Found in the Lightning Ridge opal fields, NSW, the opalised jaws date back to the Cenomanian Age of the Cretaceous Period, between 102 million to 96.6 million years ago.

From Science Daily ● May 27, 2024

The faces are made by hand in Los Angeles and Ojai with recycled metals and Australian opal eyes.

From Los Angeles Times ● Nov. 2, 2022

In my parent’s creamy bedroom I sat at Mum's dressing table, spiked my hair with L’Oréal hair mousse, daubed an Adam Ant stripe across my face, and held her opal brooch over one eye.

From "Black Swan Green" by David Mitchell

We heard from a mother, Opal Foster, whose 18-year-old son has Down syndrome and lives at home as he strives to become a chef.

From Salon ● Apr. 29, 2026

“Every tool has a work-around, and teenagers are smart, so we haven’t really made Opal be the enforcer,” Church said.

From Los Angeles Times ● Dec. 31, 2025

Deputy Chief Constable Jayne Meir, the NPCC's first lead for freight crime, said a new team at Opal - a police intelligence unit tackling organised acquisitive crime - would start targeting the issue next year.

From BBC ● Nov. 17, 2025

Santos said a software issue affecting safety systems on board the BW Opal floating production storage and offloading unit had led to an unplanned shutdown of around two weeks last month.

From The Wall Street Journal ● Oct. 16, 2025

Opal had fallen asleep by the fire, her head resting on a pile of gold.

From "Rump: The (Fairly) True Story of Rumpelstilskin" by Liesl Shurtliff

There are also pink opals, pink malaya garnets, pink topaz.

From Seattle Times ● Nov. 17, 2022

At moments, as the rays of the setting sun flooded across the Potomac River, the upper branches of many trees seemed to glow as might a sea of opals and rubies.

From Washington Post ● Apr. 2, 2022

Some of Ms. Harris’s designs come in solid gold and others in platinum; many are clustered with brilliant diamonds or opals.

From New York Times ● Jan. 27, 2022

From the window seat of a 737, they look like flickering blue opals embedded in a matrix of dusty greenery and concrete.

From Los Angeles Times ● Jul. 13, 2021

Draco paused to examine a long coil of hangman’s rope and to read, smirking, the card propped on a magnificent necklace of opals, Caution: Do Not Touch.

From "Harry Potter And The Chamber Of Secrets" by J. K. Rowling