October Birthstone Opal: Origins, Types & Seven Eras
October has two birthstones. Opal held the month by itself for centuries, and tourmaline was raised to an equal partner only in 1952.
A single novel cost opal its reputation. Sir Walter Scott killed off a character through her opal in 1829, and the stone carried a bad-luck name for the next fifty years.
An opal’s color is not pigment. The stone is packed with microscopic silica spheres, and where they stack evenly they split white light the way a prism does.
Opal is the softest stone in regular jewelry use, 5.5 to 6.5 on a scale where diamond is 10. That is why so many antique opals sit in protective closed bezel settings.
Art Nouveau jewelers made opal their signature stone. Art Deco dropped it almost entirely, because a color that shifts as you move cannot repeat inside a strict geometric pattern.
Sir Walter Scott published a novel in 1829 and cost a gemstone fifty years of its good name. Scott had invented the historical novel, and by then he was the most widely read novelist in Europe. His authority rested on getting period detail right. So when he gave a stone a supernatural property, readers took it for folklore he had found rather than fiction he had invented. In Anne of Geierstein, Lady Hermione wears an opal in her hair that brightens and darkens with her moods. A drop of holy water strikes it at a christening. The fire goes out. By morning she is a small heap of ashes. Before that book, opal stood for the opposite. Natural History, the closest thing Rome had to an encyclopedia, ranked opal fourth among all gems, behind only diamond, pearl and emerald. The same first-century account records that Mark Antony outlawed a senator named Nonius over an opal ring. By that telling, Nonius left Rome with that one object out of all he owned.
The pushback began at once. Edwin Streeter, writing in 1877 while the belief was still doing damage, named Scott's novel as the cause and predicted that "it is inevitable that the idea of ill-fortune attending the wearing of the Opal, should go the way of all superstitions." He was right. Opal's color comes from a structure no one could photograph until 1964. Its design history swings harder between eras than any other stone on the calendar. And it shares October with a gem that joined the list for the plainest reason there is.
- Why Is October Birthstone Opal?
- Are Opals Really Bad Luck?
- What Makes an Opal's Color Move?
- What Are the Different Types of Opal?
- How Did Jewelers Use Opal From Georgian to Mid-Century?
- Is Opal Durable Enough to Wear Every Day?
- What Should You Look for in an Antique Opal Piece?
- How Do You Care for Opal Jewelry?
- Why Does October Also Have Tourmaline?
Why Is October Birthstone Opal?
Opal was October's only birthstone when the American National Retail Jewelers Association set the list in Kansas City in August 1912. Tourmaline appears in the same document as an alternate, not an equal.
The meeting solved a business problem. Birthstone assignments varied by country, by tradition, and in practice by whatever a jeweler had in the case, and the group wanted one American reference. Opal was the obvious pick. It had held October in the older European tradition, in loose circulation since roughly the 1400s, and kept the month even at the height of the superstition.
One man objected in print. George Frederick Kunz was Tiffany's vice president, appointed at twenty-three, and his 1891 book Natal Stones had made a standard American list possible. A year later he reprinted the new table in The Curious Lore of Precious Stones (1913) and disagreed with it. The verdict was blunt: "For October neither the tourmaline nor the opal is as appropriate as the beryl." He had a second complaint about tourmaline alone, a gem "only known in modern times or since the eighteenth century" and so "out of place in the list of birth-stones." The list went ahead anyway. Tourmaline stayed an alternate for forty years, until the Jewelry Industry Council's 1952 revision raised it to a full co-birthstone, for reasons that had nothing to do with age.
An opal fills its own outline and does something different every time the hand moves
The British list is different. The National Association of Goldsmiths adopted it in 1937, gave October to opal alone, and has added no second stone since. A British and an American jeweler can still disagree about the month.
The name is older than any committee. Opal comes from the Sanskrit upala, precious stone, by way of the Latin opalus. It also marks the fourteenth wedding anniversary. The birthstone jewelry guide lays out all twelve months, and September's sapphire and November's citrine and topaz are the neighbors most often confused with October's pairing.
Are Opals Really Bad Luck?
No. The superstition is younger than much of the jewelry people have avoided because of it. Scott's readership was enormous and his gothic machinery was taken seriously. Within a generation opal had a trade problem with no precedent in the earlier record.
That record says the opposite. The Roman account from 77 CE still gives the best short description of play-of-color: the fires of carbunculus, the flashing purple of amethyst, the sea-green of smaragdus, "all combined together in incredible brilliance." Medieval church treasuries and Gothic royal crowns both held opals. No one was avoiding this stone.
Streeter's prediction held, and Queen Victoria is a large part of why. She was a consistent and earnest opponent of the belief, and her influence did much to make opals fashionable again. By the 1890s they were common bridal gifts. Emperor William of Germany gave Empress Augusta a parure of Australian opals, and the Duchess of Marlborough owned one of the finest opals of the period. By 1915 a standard reference could record that the stone had "long since emerged from the slight cloud of disfavor."
Where the idea came from is probably not literary. It is the fragility of the stone. An opal that crazed or lost its play on the hand looked, to an 1800s eye, like a stone that had turned against its owner. The story of a cursed Spanish royal opal ring, blamed for deaths in the 1870s, is better explained by the cholera then moving through Madrid.
What Makes an Opal's Color Move?
Play-of-color is structural, not chemical. No pigment is doing the work. Opal is built from tiny spheres of silica in neat three-dimensional arrays. When those spheres run roughly 150 to 400 nanometers across, they split white light into color. The flash you see travels as the stone turns.
Sphere size decides which colors appear. Small spheres reach the blue and violet end and stop there. Larger ones carry through green and orange into red, which is why red in the play is rarer and more wanted. Packing counts as much as size. Neat spheres give play-of-color. Random ones give common opal, which can be handsome and has no fire in it at all.
Opal is hydrated silica, silicon dioxide holding water, and the water runs from 1 to 21 percent, usually 6 to 10 in gem-grade stone. It never formed crystal faces, growing instead as rounded nodules and crusts.
The standard gemology text of 1904 blamed play-of-color on a network of fine internal cracks, formed as the stone hardened out of a silica gel, some of them lined with opal of a different refractive index. The interference physics is real, and so is the gel. What the period could not see was the scale. In 1964, researchers at Australia's CSIRO put precious opal under an electron microscope and photographed the sphere arrays. The answer was neat geometry, not cracks, invisible until then.
What Are the Different Types of Opal?
Opal is sorted first by body color, the background the play appears against.
Black opal has a dark gray to black body and sits at the top, because a dark background makes the play read as stronger. Lightning Ridge in New South Wales defined it. White and light opal has a white to cream body, mostly from Coober Pedy in South Australia. Crystal opal is clear to semi-clear, the color visible through the stone rather than on a background behind. Jelly opal is the cloudier version, common in Ethiopian stone. Boulder opal is a thin seam still attached to the Queensland ironstone it grew in, cut with the host rock as backing. Contraluz is the rarity, showing color in light that passes through it.
Fire opal breaks the pattern, valued for body color instead of play. Mexican fire opal from Villa Seca near Zimapan, in Hidalgo, runs from light brownish-yellow to deep brownish-red. Alexander von Humboldt brought it to Europe in quantity around 1800. Some fire opal shows play and some shows none. The orange is the point either way.
Pattern is the third axis, and the trade names are old. Harlequin is close-set angular patches in a mosaic. Flame opal is color in bands and streaks. Gold opal glows across the whole face. Girasol is near-clear with a traveling wave of blue. Broad, distinct patterns rank above fine pinfire.
Two more categories are constructions, not stones. A doublet is a thin slice of precious opal glued to a dark backing, which gets the look of black opal out of far less stone. A triplet adds a clear quartz or glass cap that guards the opal and magnifies its color. Both are legitimate, and both have to be disclosed. Australia supplies most of the world's precious opal, and Ethiopia's Wollo Province, opened at scale in 1994 and again in 2008, is the big modern addition. Filigree's opal and tourmaline jewelry spans body colors, sources and eras.
How Did Jewelers Use Opal From Georgian to Mid-Century?
Opal's design history tracks how much unstable color each era could take, and each era left evidence in the metalwork.
Before the Georgians. Opal's early European life belonged to the church and the crown, in treasure inventories rather than in what people wore. The Hungarian deposit near Czerwenitza in the Tokaj-Eperies mountains supplied nearly all the fine opal in European jewelry for centuries, worked from at least the 1300s, on ground the Romans had probably worked first.
Georgian (1714 to 1837). No Georgian opal jewel turns up in the sources behind this article, so the honest version is textual. Opal's Georgian presence is in acrostic jewels, where the first letters of a row of stones spelled a word: REGARD in ruby, emerald, garnet, amethyst, ruby, diamond, and DEAREST in seven more. Names worked that way too, and SOPHIA is where opal takes a place: sapphire, opal, peridot, hyalite, iolite, amethyst. The form began in the Georgian period and peaked under Victoria, so most acrostic rings that survive are Victorian. The Georgian default was the closed-back collet: each stone in its own metal cup, back sealed and often foiled, a setting built for candlelight. Opal would be set almost that way for the next century and a half, for a completely different reason.
Victorian (1837 to 1901). This is the era that rebuilt the stone's name and changed how an opal looked. The Hungarian workings were an industry: about 150 miners at Czerwenitza by 1877, a cutting works on site, and galleries on Libanka mountain four or five levels deep through four and a half miles of tunnel. Hungarian stones were the trade standard because they held their color, where Mexican opal went opaque or clear with age. Greek and Turkish merchants carried them east through Constantinople and on to Amsterdam, so they reached the market as "oriental opal," an eastern name a Central European stone never earned.
Then the supply changed. A hunter came across opal at White Cliffs, New South Wales, by accident in 1889, in white Cretaceous rock. Australian stones were cloudy or milk-white, and they spread their blues, greens and reds across far larger faces than Hungarian stone did. Within a decade the field's output reset what buyers expected, and that broad color arrived just as designers needed it.
Victorian construction is specific and checkable. Opal was cut en cabochon almost without exception, because facets fight the color and a soft stone loses a sharp edge fast. The standard mount was a blackened case ringed with small diamonds or colored clear stones. A thin stone got a backing of variegated foil, peacock feather, or polished mother-of-pearl to push the color forward. A border of small opals ran the other way too, set around a large diamond, ruby or sapphire. Matching stones to a costume also came into fashion, and opal suited every color, which made it the only safe pick in the case. Marcus and Co.'s brooch of about 1900, gold with opal and enamel, sits in the Metropolitan Museum of Art on the seam between this rescue and what came next. The history of Victorian engagement rings covers the period's construction vocabulary.
Art Nouveau (1890 to 1910). Opal is the defining Art Nouveau gemstone, and the reason is a reversal. Victorian jewelry ranked stones by market position and put the dearest one at the center. Art Nouveau treated gems as paint, picked for color, translucency and organic texture. A carved horn dragonfly with plique-a-jour wings and opal eyes could cost more than a diamond cluster, because the price followed the work, not the stone.
Rene Lalique used opal for what it could suggest: light moving through water, the shine of an insect wing. Henri Vever set opal accents against plique-a-jour enamel and baroque pearls, using a pearl's odd shape as a cloud or a wave crest. Georges Fouquet worked the same logic with Alphonse Mucha. Cabochon cutting was a flat rejection of Victorian faceting. En tremblant mounts, spring-set so the element moves with the wearer, went with opal and moonstone because an optical effect needs movement to perform. Art Nouveau jewelry leaned hard on which stones a maker could get, and White Cliffs is part of why the movement looks the way it does.
Edwardian (1901 to 1915). Opal barely appears, and that is the honest answer. The Edwardian palette was platinum, diamonds and pearls, all white, built on openwork that read as woven lace, and color entered only as a rare exception. Opal's work in these years happens in the Arts and Crafts tradition running alongside, where handwork mattered more than light. Augustus F. Rose's necklace of 1917, sterling silver with blue enamel and opal, in the Smithsonian American Art Museum, is the American version.
Art Deco (1920 to 1935). Opal fell out of Deco fashion for structural reasons rather than superstitious ones. Art Deco was built on symmetry, hard geometry and faceted stones cut to repeat inside a pattern. A calibre-cut sapphire fits a channel and behaves the same in every position. An opal fills its own outline and does something different every time the hand moves, which makes it useless in repeats.
The exceptions are dated and named. Fred Partridge made a gold, enamel and opal brooch in 1928, now in the Victoria and Albert Museum. Georg Jensen made a silver brooch set with labradorite and opals between 1915 and 1930, also in the V&A. Marie Zimmermann made a gold, amber and opal brooch around 1926, now at the Art Institute of Chicago. All three worked in the Arts and Crafts and studio traditions beside high Deco rather than inside it. Opal did not survive the 1920s among the houses selling geometry. It survived among makers whose whole argument was that the stone came first.
Retro and Mid-Century (1935 to 1970). Studio makers brought opal back quietly, again outside the major houses. John Donald set fire opals in gold, and Hermann Junger built gold brooches with emeralds, sapphires and opals. The commonest form left from these decades is the one that turns up most in estate inventory: a large cabochon opal in a gold cocktail mount, often with a diamond halo. That is Victorian construction logic in a mid-century silhouette.
Is Opal Durable Enough to Wear Every Day?
Opal is the softest stone in regular fine-jewelry use, 5.5 to 6.5 on the Mohs scale. The setting decides this question more than the stone does.
Hardness and toughness are separate things, and opal splits them oddly. It has no cleavage, so it will not part along an inner plane the way a diamond can. It is brittle, so an exposed edge chips under impact. And it is soft enough that house dust, largely quartz at Mohs 7, dulls a polished face over years.
The second issue belongs to this stone alone. Opal carries several percent water by weight as part of its structure. Lose that water and the stone crazes, a network of fine cracks inside it that no repolishing removes. Some stones give it up at room temperature. The old fix was to soak the stone in oil, which brought the play back until the oil broke down and left a dirty brown cast.
The modern version is Australian against Ethiopian. Most Ethiopian opal is hydrophane: it drinks water and other liquids. It can turn clear for a while in a sink, and a fast move from a steamy bathroom into dry air conditioning is a real risk to it. Australian opal is mostly non-hydrophane and stays put. One trade rule is worth carrying. A stone that has stayed sound through twelve or more months of dryness is unlikely to start crazing later.
So the setting is the decision. Bezels that wrap the girdle, low halos and deep baskets take the impact the stone cannot. Victorian jewelers were already doing that, and a closed case darkened the background too. A pendant, a brooch or earrings can go a lifetime without a hard knock. A ring on a working hand takes all of them. An opal ring is entirely wearable. It is not the ring to garden in.
What Should You Look for in an Antique Opal Piece?
With an antique opal you are reading two things at once: the piece, and the stone's last hundred years.
Start with construction, which dates the mount before the stone tells you anything. Antique opal is nearly always cabochon, so a faceted stone in an old mount deserves a second look. Closed backs, foil and mother-of-pearl backing point early. A border of small diamonds is the standard Victorian and mid-century treatment. Pierced filigree with trilliant, old European and single-cut accents points to the 1920s and 1930s. The metalwork narrows the date, and the stone either agrees with it or raises a question.
Condition comes next. Crazing shows as a fine network inside the stone, easiest to see with a loupe against soft light, and it spreads rather than staying put. A stone soaked in oil long ago carries a dull brown cast. Then ask about replacement. Opal is the stone in a century-old piece most likely to have been swapped, and one whose color, cut and wear do not match the mount deserves a direct question.
For the stone itself, Pliny's test still works as a first pass. Hold the stone against direct light and turn it. A real opal throws its colors more strongly from one part than another as the angle changes. Glass shows, in his phrase, "one unchanging colour which is spent at its source."
Assemblies need their own checks. A doublet shows a straight seam in profile where the opal slice meets its dark backing, so look at the girdle edge-on rather than face-up. A triplet is harder, because the quartz cap hides the join. Put it in water and the cap turns clearer, and the layers show. Specific gravity settles neither case, since the density reflects the glue and backing as much as the opal. Both have to be disclosed, so the question is always fair to ask.
How Do You Care for Opal Jewelry?
Warm water, mild dish soap, a soft brush or cloth, and nothing else.
The two real hazards are machines. An ultrasonic cleaner drives fast pressure change through a stone that holds water. A steamer adds a fast heat swing on top. Neither belongs anywhere near an opal, at any age. Hairspray, chlorine, acetone and house cleaners attack the polish rather than the stone.
Storage is where good intentions go wrong. The mistake is rarely the jewelry box. It is the dry safe and the sunny windowsill, which pull water out of the stone over time. A soft pouch away from heat and light is enough, and it keeps a harder stone from resting against the opal. Hydrophane opal needs one more courtesy. If it has been in water, let it dry slowly and away from heat instead of toweling it off and putting it away.
A crazed or damaged opal can also be replaced in a period mount without touching the old metalwork. That is part of why so much 1800s opal jewelry has survived to be worn now. The jewelry care guide covers cleaning by stone type.
Why Does October Also Have Tourmaline?
Tourmaline joined October because opal is soft. The Jewelry Industry Council's 1952 revision added it to give the month a stone that could take daily wear, and at 7 to 7.5 on the Mohs scale it does.
That change came as a batch: alexandrite to June, citrine to November, tourmaline to October, zircon confirmed for December, each giving buyers a tougher or easier-to-find stone beside the first. Tourmaline had been sitting in the 1912 table as October's alternate, so 1952 promoted a candidate already in the room.
Kunz's objection was about age, and the facts were on his side. Dutch traders brought tourmaline to Europe from Ceylon, and the name comes from the Sinhalese turmali, stone with mixed colors. Europe prized the physics before the color. Tourmaline is pyroelectric. Heat a crystal and it pulls in ash and light debris, which earned it the Dutch nickname Aschentrekker, ash-attractor. Franz Aepinus showed in 1756 that the effect was electric, not magnetic. Benjamin Franklin wrote to Dr. William Heberden of London about it in 1759 and kept a specimen on a pivot ring to show it off. A stone that arrived as a lab curiosity is an odd thing to find on a list built out of age.
America found it early and by accident. In the autumn of 1820, Elijah Hamlin and Ezekiel Holmes, two students with an interest in minerals, spotted a flash of green crystal at the roots of an uprooted tree on Mount Mica in Oxford County, Maine. Benjamin Silliman of Yale confirmed the find, recorded in an 1895 history of the site. Mount Mica became the first American gem field of consequence.
The stranger chapter is Californian. Between 1902 and 1910, demand from the Chinese Empress Dowager Cixi moved roughly 120 tons of gem-grade pink tourmaline out of the Mesa Grande district in San Diego County. Tiffany's gemologist J.L. Tannenbaum ran the trade, wiring funds from a Chinese government account at a New York bank to put local ranchers to work as miners. Cixi was reportedly buried with a pink tourmaline pillow. She died in 1908, the Qing dynasty fell in 1911, and the mining stopped because the buyer was gone.
Tourmaline comes in more colors than any other gem species, which is the plain reason it earns the month. Rubellite is the red to pink-red end, indicolite the blue, chrome tourmaline the deep green, canary the yellow, and watermelon the bicolor crystals that run pink at the core and green at the rind. Paraiba is the outlier: copper-bearing, neon blue-green, found in the Brazilian state it is named for in the 1980s and later in Mozambique and Nigeria. Tourmaline marks the eighth wedding anniversary. Both stones sit together in Filigree's opal and tourmaline jewelry, which settles which one is "really" the birthstone. The calendar has held both for more than seventy years.
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Opal & Tourmaline Jewelry
Both of October's stones in one place, from Victorian cabochon opal to Paraiba, rubellite and green tourmaline.
Browse October Stones →Cocktail Rings
Where most estate opal lives: substantial cabochons in gold and platinum mounts, Victorian through Mid-Century and modern.
Browse Cocktail Rings →Birthstone Jewelry Guide
The complete birthstone calendar with Filigree's pieces for every month of the year.
View the Guide →A stone that has been argued over
Opal is the only stone on the birthstone calendar whose name has been argued in print for two centuries, and that argument beats any list of properties. Scott's novel damaged it in 1829. Queen Victoria worked against that for decades. Art Nouveau built part of a movement on what the stone could do, and Art Deco had no use for it.
What survives is a stone whose color comes from structure rather than pigment, set much the same way for a hundred and fifty years because that way works. The full range across both of October's stones is in the opal and tourmaline jewelry.
Ready to Find Your October Stone
From Victorian cabochon opal and Art Deco filigree to black opal and Paraiba tourmaline, the collection carries both of October's stones.
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October Birthstone Opal
Is opal the same as moonstone or labradorite?
No. All three show an optical effect, but they are separate minerals doing separate things. Opal's play-of-color comes from diffraction through stacked silica spheres. Moonstone's adularescence and labradorite's labradorescence come from light scattering between layers inside a feldspar crystal.
Does an opal really need to avoid all water?
No. Warm water is the correct way to clean one. What opal cannot take is rapid change, which is what an ultrasonic cleaner or a steamer delivers. Hydrophane opal from Ethiopia drinks water and should be allowed to dry slowly, away from heat.
Is Ethiopian opal as durable as Australian opal?
Generally not. Most Ethiopian opal is hydrophane and reacts to moisture and humidity swings in a way Australian opal usually does not. It is worth asking about rather than a reason to rule the stone out.
What anniversary is opal?
The fourteenth. Tourmaline, October's other stone, marks the eighth.
Can opal and tourmaline be worn together?
Yes, and October pieces sometimes pair them deliberately. The caution is hardness rather than style. Tourmaline at Mohs 7 to 7.5 will scratch opal at 5.5 to 6.5, so store them in separate compartments rather than loose in one pouch.
