[ oh-puhl ]
/ ˈoʊ pəl /
Save This Word!

a mineral, an amorphous form of silica, SiO2 with some water of hydration, found in many varieties and colors, including a form that is milky white.
an iridescent variety of this that is used as a gem.
a gem of this.
Smoothly step over to these common grammar mistakes that trip many people up. Good luck!
Question 1 of 7
Fill in the blank: I can’t figure out _____ gave me this gift.

Origin of opal

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

Other definitions for opal (2 of 2)

[ oh-puhl ]
/ ˈoʊ pəl /

a female given name.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022


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.

Where does opal come from?

The first records of the word opal come from the 1300s. It comes from the Greek opállios, meaning “opal” or “gem.” The word may be related to the Sanskrit upala, meaning “precious stone.”

Opal is an amorphous hydrated silica mineral. The word hydrated indicates that water is a large part of its makeup (up to 20%). Opal is found in igneous rocks, often around hot springs. It is also found in the shells of some marine organisms.

Some opal is synthetic, meaning it is manufactured.

Did you know ... ?

What are some other forms related to opal-like?

  • opal-like (adjective)

What are some words that often get used in discussing opal?

How is opal used in real life?

Opal is commonly used in jewelry and is known for its iridescent qualities.



Try using opal!

True or False?

Precious opal is considered a gemstone, but it does not have a crystalline structure.

How to use opal in a sentence

British Dictionary definitions for opal

/ (ˈəʊpəl) /

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

Derived forms of opal

opal-like, adjective

Word Origin for opal

C16: from Latin opalus, from Greek opallios, from Sanskrit upala precious stone
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for opal

[ ōpəl ]

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.