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Learn about opal, a gemstone with the colors of the rainbow, from its formation, interaction with light, and unique patterns. Explore opal's history, lore, treatments, synthetics, and more on GIA's website.
- Research
Opal is the product of seasonal rains that drenched dry...
- Buyer's Guide
Opal is the product of seasonal rains that drenched dry...
- Opal History and Lore
Opal is considered an October birthstone. Some people think...
- An Introduction to Synthetic Gem Materials
Synthetic ruby can be produced via flux growth processes...
- Opal Description
"The Path of Enlightenment" necklace contains 180...
- Research
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- Chemistry
- Uses
- Availability
- Formation
- Examples
- Names
- Appearance
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Gem-quality opal is one of the most spectacular gemstones. A single stone can flash every color of the spectrum with an intensity and quality of color that can surpass the \\"fire\\" of diamond. The best opals can command prices per carat that rival expensive diamonds, rubies and emeralds. Opal is one of the most popular gems.
Opal is a hydrous silicon dioxide (SiO2.nH2O). It is amorphous, without a crystalline structure, and without a definite chemical composition. Therefore it is a \\"mineraloid\\" rather than a \\"mineral.\\"
Opal is a wonderful stone for earrings, pendants, brooches and rings. However, it is softer than most other gemstones. Opal has a hardness of about 5.5 to 6.0 on the Mohs hardness scale. Because of that opal is best suited for use in earrings, brooches and other pieces of jewelry that rarely encounter scuffs and impacts. To protect the fragile opal...
Opal is a very common material that is found throughout the world. Most of this opal is \\"common opal\\" or \\"potch\\" which has a milky or pearly luster known as \\"opalescence.\\" However, rare specimens of opal produce brilliant color flashes when turned in the light. These color flashes are known as a \\"play-of-color.\\" Opal specimens that exhibit ...
Areas within an opal that produce a play-of-color are made up of microscopic spheres of silica arranged in an orderly network. This network of spheres acts as a diffraction grating. As the light passes through it is diffracted into the colors of the spectrum. The size of the spheres and their geometric packing determine the color and quality of dif...
Famous mining areas in Australia include: Coober Pedy, Mintabie, Andamooka, Lightning Ridge, Yowah, Koroit, Jundah, and Quilpie. Other countries that produce precious and fancy varieties of common opal include: Mexico, Hungary, Indonesia, Brazil, Peru, Honduras, Guatemala, Nicaragua, Slovakia, Czech Republic, and Ethiopia. Opal has been produced in...
There are many types of opal, and a wide variety of names are used to communicate about them. If you have spent a small amount of time looking at opal, you have probably been surprised by this extensive vocabulary of wonderful names. There is actually a logic behind names such as fire opal, black opal, boulder opal, matrix opal, Coober Pedy, Mintab...
\\"Precious opal\\" flashes iridescent colors when it is viewed from different angles, when the stone is moved, or when the light source is moved. This phenomenon is known as a \\"play-of-color.\\" Precious opal can flash a number of colors such as bright yellow, orange, green, blue, red or purple. Play-of-color is what makes opal a popular gem. The de...
Precious opal is very rare and found in a limited number of locations worldwide. Most precious opal to date has been mined in Australia. Ethiopia and Mexico are secondary sources of precious opal. Precious opal is also mined in Brazil, the United States, Canada, Honduras, Indonesia, Zambia, Guatemala, Poland, Peru, and New Zealand. The accompanying...
\\"Common opal\\" does not exhibit \\"play-of-color.\\" It is given the name \\"common\\" because it is found in many locations throughout the world. Most specimens of common opal are also \\"common\\" in appearance and do not attract any commercial attention.
If you understand the difference between precious opal and fire opal, here is another variation. This opal from Ethiopia has an orange bodycolor, making it a fire opal, and it also contains an electric green to purple play-of-color, making it a precious opal. So, we might call this a precious fire opal. Much of the Ethiopian opal currently being pr...
\\"Morado\\" is the Spanish word for \\"purple.\\" Some common opal with a purple bodycolor produced in Mexico has been given the name \\"Morado Opal.\\" The stones in the accompanying photos are nice examples. The stone on the left is a 19-millimeter round, and the stone on the right is a 13x26-millimeter teardrop.
Andamooka is one of the early mining districts of South Australia. Commercial production began there in the 1920s. The area is famous for its matrix opal. The stone in the photo is a cabochon cut from Andamooka matrix and weighs about 30 carats.
Honduras is well known for producing a black, basalt-matrix opal that contains tiny vesicles filled with play-of-color opal. Most people who know opal will understand exactly what you are talking about if you use the term \\"Honduras Black Opal.\\" The specimen shown is a bead cut from Honduras Black Opal.
Lightning Ridge is a town in New South Wales, Australia that has become world-famous for its deposits of black opal. More black opals have been produced at Lightning Ridge than at any other location in the world. The specimen on the left is a solid black opal with a strong blue face-up color mined at Lightning Ridge. It is 2.46 carats in weight and...
Most cut opals are solid stones. The entire stone is cut from a single piece of rough (see top illustration). However, some opal rough has very thin but brilliant layers of play-of-color material. Some artisans cut the stone down to the thin color layer and glue it to a base of obsidian, potch, basalt, or plastic - then cut a finished stone. These ...
\\"Synthetic opal\\" or \\"lab-created opal\\" or \\"lab-grown opal\\" are some of the names used for opal that has been made by humans. These opals are made from materials that have the same chemical composition (hydrated silicon dioxide) as natural opal. They can have spectacular play-of-color and a beauty that rivals some of the best natural opals.
Learn about the different types of opal, such as fire, boulder, common and precious, and their physical and chemical properties. Discover how opal can display play-of-color, a phenomenon of diffraction of light into its component colors, and how to care for it as a gemstone.
Opal is a hydrated amorphous form of silica (SiO 2 · n H 2 O); its water content may range from 3% to 21% by weight, but is usually between 6% and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline forms of silica, which are considered minerals.
- Amorphous
- Mineraloid
- Opl
Learn about the unique properties, history, and value of opal gems, the most delicate and colorful gemstones commonly worn. Find out how to identify, appraise, and buy opals of different types, such as black, fire, crystal, and boulder opals. Discover the difference between common and precious opals, and the meaning of opal's play of colors.
Aug 11, 2021 · Opal is a gemstone that forms in a variety of different colors, shapes, and sizes. Unlike most gemstones, opal isn't a mineral but a mineraloid. The composition is a hydrated (wet) amorphous silica with a Mohs hardness scale ranking between 5.0 to 6.5.
Oct 1, 2023 · Learn about the history, science and varieties of Opal, the 'queen of gems' that changes colour with the light. Discover how Opal was valued, traded and worn by ancient and modern civilisations across the world.
