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 Jewel History blog have been treated to her weekly (someti… [read review or visit site]



Clubs & Associations

Other Great Reference Sites

Most watched eBay auctions    

Diamond 6.40ct Opal 18k Yellow Gold Ring 5.2 Grams Nr18ct/ 18k Gold Diamond & Opal Fine Victorian Cluster Ring, 750**antique Platinum Opal Ring 17x11.7mm Size 8.25 2.4 GramsVtg Victorian Revival Givre Amethyst Opal Art Glass Mesh Chain BraceletEstate 8.09ctw Natural Opal And Diamond Ring In 14k Yellow Gold **antique 14k Yellow Gold Ruby Garnet Opal Ring 0.5x0.75" 6.5 Grams Size 7.5Victorian Design Ladies Opal & 9ct Gold Cluster Ring F0765Vintage Jewellery Beautiful Silver & Australian Opal Pendant NecklaceVintage 14k Opal & Shapphire Cluster RingAntique Victorian 14k Y Gold 1.2ctw Natural Round Cut Opal & Garnet Floral Ring Antique Ladies 18ct Yellow Gold Diamond & Opal Ring - Size N (a91)Vintage 10kt Yellow Gold 1.75ct Opal & Diamond 7.0" Tennis Bracelet 3.3grVintage Opal Ring. Large Oval. 10k Gold Vintage Estate Ornate 14k Yellow Gold 4 Genuine Cabochon Opal Scrolled Ring Sz 718ct/18k Gold Pair Of Victorian Opal And Diamond Drop Star EarringsFine 10ct / 10k Gold And Opal Stud Earrings Art Deco Design Opal & 9ct Gold Cluster Panel Ring F0768Estate 8.92ctw Natural Opal And Diamond Ring In 14k Yellow Gold 18k/18ct Gold Opal Ruby And Diamond Heavy 'bug' Brooch 750Antique 14k Gold Estate Signed Sb Large Fire Opal Diamond Accent Art NouveauVintage Very Nice Big White Opal & 4 Diamond Ring 14k Gold Antique Victorian Edwardian 15ct Gold Fiery Opal Tie Stick Cravat Pin18ct/18k Gold Opal, Emerald & Diamond Gold Victorian Snake Tie/stick Pin BoxedEstate $1200 10k Yellow Gold 1.15 Ct Natural Colorful Oval Opal And Diamond RingVtg Handmade 10kt Yellow Gold 1.00ct Opal & Diamond 7.0" Tennis Bracelet 3.3grEstate 5.23ctw Natural Opal And Diamond Ring In 14k Yellow Gold Vintage Big Fiery Australian Opal Cluster & Pearl 14k Gold Domed Cocktail RingEstate 6.75ctw Natural Opal And Diamond Ring In 14k White Gold 18ct/ 18k Gold Diamond & Opal Victorian Style Ring, Bm, 750Fine Vintage Opal & Sapphire Gold Ring 9k 9ct 375Estate 7.89ctw Natural Mexican Fire Opal And Diamond Ring In 14k Yellow Gold Fine 10ct / 10k Gold Opal Mexican Stud Earrings Estate 5.02ctw Natural Mexican Fire Opal And Diamond Ring In 14k Rose Gold Estate $3000 14k Yellow Gold Natural Colorful Oval Opal And Garnet Ring 0.90 CtsVintage 14k Gold Filigree Ultra Fine Natural Opal Filigree Earrings NrLarge Vintage 9ct Gold Precious Opal Solitaire Rope Twist Border Ring Size MEstate $1300 14k Yellow Gold 1.15 Ct Natural Colorful Oval Opal And Diamond RingVintage 925 Silver Gorgeous Green Blue Opal Flowers Link 16" To 18" NecklaceVintage Eton 1.3ctw Fiery Opal Sterling Gold Wash Gilt Bangle Clamper BraceletAmazing Vintage 14k Gold Colorful Natural Black Australian Opal Diamond RingFine Opal Doublet Earrings And Matching 9ct Gold Ring 9k 37542.75ct Natural Ethiopian Black Opal Play Of Color Facet Rough Specimen Yzo3140rFine 9ct / 9k 375 Gold And Opal Doublet Pendant Vintage 14k Yg Opal Earrings Leverback 17.5 Mm Long Immaculate NrLadies Antique Elegant 14k Solid Yellow Gold Opal & Diamond Lapel Pin Brooch Nr**estate 14k Yellow Gold Opal 20pts Diamond Ring H-i I1 3.9 Grams 8x5.6mm Size 5**estate 14k Yellow Gold Jelly Opal Ring 6x7.3mm 3.1 Grams Size 4.75Vintage Pair Fiery Opal 9ct Gold Pierced Ear Earrings Hallmarked Birmingham 19759ct/ 9k Gold Victorian Style Art Nouveau Three Stone Opal Ring, 375Fine Quality Vintage 9ct Gold Cabouchon Opal & Amethyst Set Ring18ct/ 18k Gold Opal,diamond & Emerald Pendant On Chain, 750Fine Black Opal Doublet Vintage 9ct Gold Earrings 9k 375Stunning Opal Cabochon Ladies 9ct Gold Cocktail Ring F0761Stunning Pair Of 3.00 Carat Opal & 9 Ct Gold Stud EarringsVintage Tru Glo 10k Gold Marquise Opal & Diamond Cocktail Ring 1.5g Size 6Estate 4.10ctw Natural Mexican Fire Opal And Diamond Ring In 14k White Gold **estate 10k Yellow Gold Opal Ring 8 X 6mm 2.4 Grams Size 7.75Stunning Opal Cabochon 9ct Gold Ladies Stud Earrings F15302.25 Ct Australian Opal Ring 14k Yellow Gold Natural Cabochon Cut White Estate14k Black Opal Diamond Vintage Ring Lightning Ridge Solid Huge 9.55 Carats!