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, 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    

14ct/ 14k Rose Gold Opal & Ganet Art Deco Ring, 585Vintage Solid 9ct Gold Opal PendantTiffany & Co. Art Deco Natural 1.75ctw Semi Black Opal & Diamond 18k Gold RingFine Large Fiery Opal And Diamond Art Deco Design 18ct Gold Ring 18k 750Scarce 1950s Amazing Color Play Pink Opal Natural Sapphire Vintage 14k Gold RingVintage Solid 9ct Gold 6 Stone Opal Brooch18k Black Opal Diamond Emerald Carved Ring Pendant Vintage Cocktail 10.35 Carats14k Solid Gold Top Quality Antique Art Deco Solid Opal & Diamond Ring Sz 4.2514k Opal Diamond Black Ring Pendant Brooch Vintage Cocktail Huge 23.55 Carats!Estate Vintage Large Natural 18.0ct Australian Fire Opal 14k Gold Drop PendantFine Victorian 2.5ct Fiery Black Opal Doublet 9ct Gold Pendant 9k 375Antique Victorian Solid 15ct Gold Opal & Ruby Ring Birmingham, England 1864Fine Victorian Style 6 Stone Fiery Opal 9ct Gold Ring 9k 375Victorian 14k Gold Enamel Diamond 35.5mm X 26.5mm Opal Cab Necklace Pendant Rdr Vintage Art Deco Mens 10k White Gold Natural Opal Matrix Ring 9 1/2 Not ScrapFine Victorian 18ct Gold 5 Fiery Opal Ring 18k 750Antique Vintage Nouveau 14k Gold Australian Fire Opal Filigree Chased Pendant!Ladies Antique Style 14k Gold Opal & Akoya Pearl Snowflake Pendant Brooch Rdr NrAntique Vintage C. 1900 Nouveau 14k Gold Australian Opal Diamond Ring! Sz 4.5Finest Vintage 9ct Gold Precious White Opal Cabochon Earrings14k White Gold Antique Opal Ring - Fiery!!! 14ct/ 14k Gold Victorian Style Opal Bangle, 585Huge 15.0ctw Natural Australian Opal 14k Gold 1960s Mens Vintage CufflinksEstate 5.96ctw Natural Fire Opal And Diamond Ring 14k Solid White GoldAntique Victorian Womens Solid 14k Yellow Gold Opal Diamond Ring Sz 8Vintage Estate 10k Yellow Gold Opal & Garnet Marquise Diamond Ring Size 7.25 N/rVtg Victorian Revival Slide Charm Foiled Opal Amethyst Glass Cuff Bracelet9ct/ 9k Gold Opal & Garnet Five Stone Victorian Style Ring, 375Vintage Gemstone Tourmaline Topaz Peridot Fire Opal Citrine 14k Gold NecklaceStunning 14k Vintage 3ct Genuine Fire Opal Tennis BraceletFine Gem Quality 2.75ct Natural Black Opal Diamond 14k Gold Drop PendantVintage 14k Yellow Gold Pear & Round Cut Opal Ladies Ring 3.6gVintage Sterling Silver - Zuni Signed Turquoise Opal Inlay Band 8g - Ring (7.25)Vintage 9ct Gold Ladies Sapphire Opal Cluster RingEstate 11.59ctw Natural Opal And Diamond Ring In 14k White Gold Estate Natural 1.02ctw Australian Opal & Diamond 14k Gold Drop Pendant NecklaceFine Sapphire And Opal Cluster 9ct Gold Earrings 9k 375Fine 5 Stone Fiery Opal 9ct Gold Ring 9k 375Vintage Natural Black Opal Doublet 10k Gold Bird Brooch~cultured Pearls~9.5 GramAntique 14k Gold Opal & Diamond RingEstate 11.41ctw Natural Opal And Diamond Ring In 14k White Gold **estate 14k Yellow Gold 31pt Diamond Opal Necklace I-j I-1 17.5 Grams 6x4mm 17"Stunning Opal Cabochon Ladies 9ct Gold Cocktail Ring F0708Beautiful Vintage Real Solid 14k Gold Opal Necklace 4 Grams No Scrap9ct/ 9k Gold Fiery Opal & Ruby Ring, 375Stunning Victorian Design Opal And White Gem Stone 9ct/9k/9carat/375 Gold Ring$1,250 1.75ct Antique Natural Australian Opal "sun & Moon" Pin 14k Yellow GoldAntique 14k 10k Yellow & Rose Solid Gold Bezel Set Opal Stick Pin ~ No Reserve Quality Vintage Frank Yazzie Old Pawn Zuni Sterling Turquoise Opal Drop EarringsVintage Silver And Opal PendantSilver Opal Sapphire Ring BeautifulA Stunning 5.00 Cts Oval Black Opal 9ct Gold Large RingFine Art Deco Design Fiery Opal And Amethyst Cluster 9ct Gold Ring 9k 375Antique Vintage Deco 14k Yellow Gold 5.13 Ct Boulder Fire Opal Necklace Pendant!Vintage Sterling Silver Oval Cut Opal Dangle Ladies Earrings 2.7g44.1ct Natural Ethiopian Black Opal Play Of Color Facet Rough Specimen Yzo4657Vintage Sterling Silver Inlaid Opal Stud Ladies Earrings 3.6gVintage 14k Gold Fire Opal Ring Signed Gemstone Art Deco Filigree Size 7 1/425ct Natural Ethiopian Black Opal Play Of Color Facet Rough Specimen Yzo4667Vtg Sterling Silver Unique 13 Multi Gemstone Charm Bracelet 7" Garnet Opal Amber