Precious opal may seem to contain every color in the rainbow, depending on which angle you look at it. This color-changing phenomenon, known as iridescence or color play, has captivated imaginations for centuries. Thanks to its flashing colors, often resembling the flecks in irises, it has been thought to bring good luck and heal to eye ailments. Other cultures associate it with bad luck and the evil eye. Not surprisingly, perhaps, it’s been employed in Rorschach-type tests in psychology.

Opal, made of hydrated or hardened silica gel, is 5 to 30 percent water, which means the stone may eventually dry out, causing it to lose its iridescence and crack. Iridescence is created by the structure of the stone, wherein tiny, tightly packed silica spheres diffract light. The bigger and more orderly these spheres, the more color the opal appears to contain.

An amorphous stone, opal is formed in the cavities of sedimentary rocks such as ironstone and sandstone. It also creates veins in igneous rocks, is found in stalagmites or stalactites in caves, and works as a petrifying agent, replacing wood, shell, and bones in fossils. Before the 19th century, Czechoslovakia was the primary source of precious opal, but these days it’s Australia. Opal is also mined in Brazil, Ethiopia, Honduras, Indonesia, Japan, Mexico, Peru, Russia, southern Africa, and in Nevada and Idaho in the United States.

Being a soft, fragile stone, opal is easy to damage and difficult to work with. Nonetheless, jewelers find its enchanting color difficult to resist. Opal is often cut into cabochons with free-form shapes that best show off the color play within. These unique shapes inspire much creativity in the jewelry design for necklaces, rings, and bracelets. Opal may be opaque to translucent to transparent. It comes in a wide range of base colors, and generally has a vitreous luster.

There are both precious and non-precious types of opal. Perhaps the most well-known of the precious is called white opal, which has a light-colored based such as white or cream and intense color play. These opals may appear washed out without a closed-back bezel setting, which bring out their iridescence.

Even more rare and desirable, though, is black opal, which has a higher carat price than white. Black opal is actually a dark-colored opal, which can be gray, blue, green, or gray-black. Less dark is the precious jelly or semiblack opal, which has a lighter base in similar colors, and may have an amber color body that creates a stunning blue-purple iridescence.

Especially rare forms of precious opals include harlequin opals (transparent to translucent opals with mosiac-like patches of color), crystal opals (completely transparent and gl...

Sometimes the matrix rock, or mother rock, like ironstone or sandstone creates bands or inclusions inside the opal. Some opal is cut to highlight such inclusions, but boulder opal is cut so the stronger matrix stone is only on the back of the cabochon, making the piece both more resilient and cheaper to purchase. Andean opal is another popular stone because of its turquoise color, usually opaque. It is believed that Andean opal will lose its color when exposed to air, so the stone is often “fixed” with a glue-like coating.

Fire opal is usually transparent and lacks the color play of other opals. It ranges in color from yellow to orange to red, with red being the most desirable. Fire opals, unlike precious opal, is often faceted and less expensive.

Common, or “potch,” opals come in three basic varieties: Honey opal, which has no color play and is often used in bead form; prase opal, which is a pretty green color thanks to the presence of nickel and has a cloudy look similar to that of chrysoprase; and seascape opal, which is a blue-green color, often with dendritic inclusions.

In medieval times, the opal was thought to bring great luck, possessing all the virtues of the various gemstones, thanks to the color play. It was believed that if you wrapped an opal stone in a fresh bay leaf, it could make you invisible. However, in Victorian times, the 1829 novel “Anne of Geierstein,” by Sir Walter Scott made the opal disreputable, described as a talisman that turned to colorless stone when touched by holy water—an event that killed the wearer. After his novel was published, the opal was believed to be a symbol of bad luck and death, and sales in Europe diminished.

Even in the early 20th century, fear and suspicion of the stone lingered, particularly with Russians, who thought the stone embodied the evil eye. That is perhaps why the opal appears in so few of the great jewelry collections of the 20th century.

The rebellious Art Nouveau artisans, though, rejected Victorian conventions and embraced the “organic” look of opal cabochons, which worked well with their insect motifs and elaborate enamel work.

Opals, being soft and subdued, are nearly the opposite of diamonds, with their hardness, brilliance, and fire. Yet these two stones complement each other well, particularly when a large opal cabochon is set within a protective ring of small, faceted diamonds.

Cartier made two pearl necklaces for Barbara Hutton featuring such opal-and-diamond clasps. One featured two rows of golden cultured pearls, and she would often wear this necklace with her beloved ruby and diamond tiara. The other was used on a strand of pearls once worn by Marie Antoinette and given to Hutton in 1933 by her father on the occasion of her marriage to Prince Alexis Mdivani.

Synthetic composite opals come in two forms: doublets and triplets. Doublets have an outer layer of precious opal, but a base of potch opal, whereas a triplet has a base of common opal, a thin layer of precious opal, and a protective covering of rock crystal. These composites can be identified by looking at them side-on with a magnifying glass.

In 1973, Gilson, the French company that developed imitation turquoise, also created imitation opal in the lab with nice iridescence but clearly fake color patterning. In the United States, John Slocum made a tough glass that resembled opal, but it lacked the texture of opal and looked crumpled under magnification. The cheapest fake opal around is made of polystryrene latex, which has a milky bluish sheen.

The most important factor in determining the quality of a piece of opal is the brightness and evenness of color. To check, turn the stone 360 degrees and make sure the iridescent color appears all across the surface, with no “dead” zones. For what it’s worth, “opalescence” is an incorrect term to apply to an opal; it refers to the the bluish-white shimmer, or “shiller,” on other gemstones, such as the moonstone.

Opals that have been drilled are more prone to dehydration, but it is possible to restore a dried-out opal by submerging it in water. Some evaporation is inevitable over time, but you can slow it by storing your opals in moist cotton balls. Opals are particular sensitive to perfume, soaps, and detergents, so opal necklaces and rings should be removed when washing or grooming.

About our sources | Got something to add?

▼ Expand to read the full article ▼

Best of the Web (“Hall of Fame”)

All About Jewels Dictionary

All About Jewels Dictionary

This incredible reference dictionary on jewelry, from Enchantedlearning.com, is both beautiful and comprehensive. S… [read review or visit site]

Morning Glory Antiques and Jewelry

Morning Glory Antiques and Jewelry

Jewelry collectors, feast your eyes on this internet gem! It's a goldmine of jewelry information featuring all styl… [read review or visit site]

Cathy Gordon's Jewelry Gallery

Cathy Gordon's Jewelry Gallery

With its vast galleries featuring clear images of jewelry and style, this site really covers it all! Divided up by … [read review or visit site]

Jewel History

Jewel History

Since March of 2007, readers of Lori Ettlinger Gross’s JewelHistory blog have been treated to her weekly (sometim… [read review or visit site]



Clubs & Associations

Other Great Reference Sites

Most watched eBay auctions    

Estate 10.50 Ct Natural Australian Opal And Diamond 14k White Gold Cocktail RingAntique Victoran 15ct Gold Emerald & Precious White Opal Wishbone Brooch Finest Vintage 9ct Gold Three Stone Precious White Opal Cabochon Ring Designer Indian Opal Amethyst Turquoise Coral 14k Gold Ring 12.4 Grams NrStunning Art Deco Design Opal & Diamond 18k Gold Cluster RingLovely Fancy Art Deco 14k Solid Yellow Gold Filigree Fiery Fire Opal Stone RingAntique C. 1900 Art Nouveau 14k Gold Carved Black Opal Jet Pearl 1.25" Earrings!Antique Art Nouveau 9ct Gold Opal And Seed Pearl Brooch.Antique C. 1900 Nouveau 14k Yellow Gold 3.83 Ct's Australian Opal Carved Ring! Antique Victorian Opal Heart & Pearl Ring - 18ct Gold Circa 1900Fine 3 Carat Opal Gold RingAntique Art Nouveau 14k Gold Seed Pearl & Opal Ring Sz 7.5 1.3 DwtAntique Art Deco 14k Yellow Gold Natural 1ctw Opal & Diamond Ladies Ring 3.9gAntique Australian 9 Carat Gold And Solid Opal Bar BroochStunning Black Opal 14k Gold RingVintage 9ct Gold Black Opal, Diamond, Ruby And Emerald Ring - SignedAntique Victorian 1800's 10k Yellow Gold Natural 1ctw Opal Floral Ring 2.5gVintage 9 Carat Gold And Australian Opal Tie PinFine Art Deco Design Opal And Peridot Gold RingAntique Art Deco 14k W Gold Filigree Pin Fire ..fireworks.. Opal Ring RingAntique C. 1850 Victorian 9k 10k Yellow Gold English Carved Opal Sapphire Ring!Ladies 14k Yellow Gold Opal Ring With 18 Diamonds - Looks VintageEstate Orange & Yellow Mexican Fire Opal 14k Gold Necklace 12.5 Grams NrDiamond Brooch Beautiful Handmade 9ct Gold Platinum Sapphire Opal Pin E48Fine Large Art Deco Opal And Ruby 14ct Gold Cluster RingVintage 14k Gold Fancy High Fashion 3.0ct Opal Dangle EarringsVintage Dragons Breath Opal Bird Stamped Oval Sterling 925 Ring 10 (11.7g)** Antique 14k Yellow Gold Opal Emerald And Diamond Stick Pin 5.3 X 7.3mm C1900 Antique Victorian 10k Rose Gold Gf Opal Pearl Slide Watch Chain NecklaceAntique Victorian 1800's 10k Yellow Gold Natural 2ctw Opal Floral Ring 4.4gAntique Victorian Opal & Diamond Ring 10k Gold Engraved Band Size 6.518ct Gold Opal Ring In Old Box** Vintage 14k Yellow Gold Opal With Seed Pearl Screw Back Earrings 6x4.8mm Rare Vintage 10k Yellow Gold 2.5ct Natural Square Cut Opal And Diamond Ring 3.4g14k Natural Opal Stud EarringsVintage Tiffany & Co Brooch/pin 14k Gold Dragonfly Opal Leather Display BoxAntique C 1920 Art Deco 14k Yellow Gold Sammartino Bro Carved Opal Amethyst RingStunning Antique Vintage 5ctw Oval Cut Natural Opal 14k Yellow Gold Ladies RingFine Art Deco 9ct Gold Opal Rare Vintage Ladies Ring Size M E46Vintage Navajo Sterling Silver & Opal Turquoise Lapis Mosaic Inlay Bracelet Stunning Antique 14k Y Gold 12ct Natural Rose Quartz And 1ctw Garnet Ring 7.9gAntique Etruscan 2ct Natural Opal Gem 14k Yellow Gold Stud EarringsFine Victorian Style Three Stone Opal Gold RingFine Pair Of Vintage 1 Carat Opal Gold EarringsGreat Antique 10k Gold Art Deco Lavalier With Opal & PearlFine Pair Of Gold Opal Drop Earrings$1,290.00 Retail Very High Polish 14kt Yg Oval Opal Art Nouveau Estate Ring |ercNr 14k Gold Natural Opal Ring Sz 5.5 Victorian Open Work 3.5 Grams Not Scrap22.5ct 100% Natural Australian Opal 14k Yellow Gold Pendant Col61Vintage 14k Yellow Gold Art Deco Classical Opal And Garnet Crown Ring Size 8*no Reserve* Fabulous Vintage Floating Opal Pendant Necklace Sterling Silver Antique C. 1920 Deco 14k Yellow Gold Carved Australian Opal Womens Earrings!Ca1910 Antique Genuine Seed Pearl & Fiery Opal Pocket Watch Chain & Slide 32.5"Antique Solid 14k Gold Gypsy Garnet & Opal Pendant - 1.8 Grams, No Reserve18k Black Opal Diamond Pendant Vintage Necklace Australian Box Huge 4.25 Carats14k Gold Vintage Estate Sapphire Opal Cocktail Ring Not Scrap Nr No Reserve .99Art Deco Inspired White Gilson Opal Onyx Earrings 925 Sterling SilverAntique Victorian Opal Seed Pearl Open Back Necklace4 Fabulous Antique Victorian Gold Filled Stick Pins - Fire Opal - Dragons BreathVintage Heavy Fine Quality Emerald Opal Solid Gold 1950s Nature Inspired Pendant