opal

¹ American  

[oh-puhl] / ˈoʊ pəl /

noun

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

• opal-like adjective

Etymology

Origin of opal

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

Example Sentences

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

Fossilised pieces of the animal's jaw bone were found in opal fields in northern New South Wales, alongside evidence of several other ancient and now extinct monotreme species.

From BBC • May 27, 2024

The fossils were found by Elizabeth Smith and her daughter Clytie of the Australian Opal Centre in Lightning Ridge, who have spent decades working and searching over the opal fields.

From Science Daily • May 27, 2024

Around him, teeth coverings sparkled on the shelves — diamond, gold, opal, some featuring designs including a pink fang-shaped outline.

From Los Angeles Times • Mar. 8, 2024

His hands were pale, with green veins and fingers that were like parasites, and he wore a solid gold ring with a round sunflower opal on his left index finger.

From "One Hundred Years of Solitude" by Gabriel Garcia Marquez