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    

Victorian 14kt Yellow Gold Black Opal Baby Sea Pearls Enamel Necklace Not ScrapVintage Large Lady's 14k Yellow Gold Australian Opal & Diamond Cluster RingAntique 5.20ct Opal 14k Gold Oval Leaves Long Ring NrC1900 Antique Victorian 10k Rose Gold Gf Opal & Pearl Watch Chain Slide NecklaceStunning Quality Antique Vintage Art Deco Design Black Opal & Diamond Gold RingRare Estate Vintage 15ct Australian Fiery Opal Diamond 14k Gold Statement RingVintage 18ct Gold Fire Opal & Diamond Ring H/mkd 1963 Sheffield Exquisite Art Nouveau 9ct Gold Opal And Seed Pearl Brooch Signed Vintage Old Pawn Navajo Sterling Jerry T Nelson Spiny Oyster Opal Inlay BraceletStunning Opal Cabochon Ladies 9ct Gold Cluster Ring F0221Vintage Estate Natural Semi Black Australian Opal 14k Gold Braided Cable RingStunning Victorian Opal And Diamond 18ct Gold Cluster RingEstate 1.00ct Opal 14k Gold Eternity Band Ring NrAntique Victorian 2 Carat Old Mine Cut Pink Sapphire & Opal Ring - 10k Gold33.85ct Natural Australian Opal 14k Yellow Gold Crab Pin Brooch Pendant Col46Finest Stunning Vintage 9ct Gold Precious White Opal Three Stone Ring Fine Pair Of Vintage Opal And Citrine Gold Drop EarringsVintage 14.58ctw Natural Hand Carved Australian Opal 14k Gold Floral NecklaceVintage 9ct Gold Opal Ring Birmingham Convention Hallmarks Uk Size O Usa 7 1/4Fine Early Victorian Opal Silver And Gold Cluster RingVintage 9ct Gold Genuine Amethyst & Opal Ring - Size O - 3.7g - Stunning!Fine 1.1/2 Carat Opal Gold Ring20.85ct 100% Natural Australian Opal 14k Yellow Gold Pendant Col48Fine Art Deco 1 Carat Opal Gold Ring30 Ct Vivid Opal Necklace 14k Yellow Gold Clasp Natural Bead 5 Mm 18 Inch LongVictorian Yellow Gold Ring With Opal In Star Offset By 5 Diamonds No Reserve!Vintage 3.10ct Opal Diamond 14k Gold Flower Cocktail Ring 7.9 Grams NrVintage Navajo Dt 925 Sterling Silver Huge Onyx Jasper Turquoise Opal Pendant NrAntique English 18k Gold Acrostic Adore Diamond Opal Ruby Emerald Ring C1900Fine Victorian Style Amethyst And Opal Gold RingPretty Victorian 15ct Gold Opal & Green Beryl Set RingFabulous Floating Opal 12k Gf Vintage Estate Opalite Pendant Necklace In BoxAntique English Victorian 9k Gold Adore Diamond Ruby Emerald Opal Ring Bham 1888Antique Victorian 10k Rose Gold 9ct Natural Oval Cut Opal Solitaire Ring 4.1gAntique 9ct Gold Ring Set Opal Fine Pair Of Black Opal Doublet Gold Drop EarringsMagnificent Quality Antique Victorian Solid 14k 14ct Gold Opal Stud EarringsRare Solid 14k Yellow Gold, 2.50 Cttw Opal & .40 Cttw Diamond Estate EarringsAntique English Victorian 9k Gold Banded Agate & Onyx Dangle Drop EarringsBeautiful Opal And Gold Stick PinVintage 14k Solid Gold 1.25ct Natural Opal Ladies Cocktail Ring Fine Sz 6.5 Nr!!Antique Victorian 1890s 1ct Natural Opal Pearl 14k Gold RingSigned Nakai Sterling Silver 925 Vintage Ring Size 7.5 Adjust Fire Opal 1170Art Deco Estate 14kt Yellow Gold 2ctw Ceylon Sapphire Opal Cluster RingBeautiful Vintage 2.00 Carat Opal Abstract PendantStunning Vintage/antique Solid 15k Gold Three Stone Opal Ring14k Solid Yellow Gold Victorian Antique Vintage Brooch Stick Pin Opal 1160Vintage Coro Signed Blue Opal Art Glass Rhinestone Floral Silver Choker NecklaceFine Victorian Rough Cut Opal And Diamond 15ct Gold BroochPair 14ct Gold Opal Stud EarringsVtg Old Pawn Cecil Ashley Navajo Sterling Opal Orange Oyster Turquoise PendantHuge Vintage Zuni Opal Channel Silver BraceletAntique 1920's 10k Y Gold 1ctw Natural Round Cut Opal Snowflake Floral Ring 3.4gEstate .51ct Australian Jelly Opal & Diamond Ring 10k Yellow Gold $1300 K925Vintage Solid 9ct Gold Opal Gem Set Stud Earrings LadiesSpectaculr Sterling Silver Opal Cluster Earrings No ReserveVintage Sterling Silver Floating Opal Pendant W/ 18" Chain NecklaceEstate Vintage 14k Yellow Gold 2ctw Natural Oval Cut Opal Filigree Earrings 3gGorgeous Vintage Rennie Macktinosh Design Silver Gilt Fiery Opal Ring Size O 1/2Antique Watch Chain Necklace Slide Hook Opal Fluer De Lis For Parts Pieces Lot 2