October Birthstone: Opal & Tourmaline
Opal and tourmaline share the designation of October birthstone, giving those born in this month a choice between two entirely different gemstones. Opal offers a shifting display of spectral colour caused by light diffracting through its internal structure, while tourmaline provides one of the widest colour ranges of any mineral. This guide covers the history, properties, and antique significance of both October birthstones, with particular attention to the opals that dominated Victorian and Edwardian ring design.
What Are the October Birthstones?
The two October birthstones are opal and tourmaline. Opal was formalised as October's stone when the American National Association of Jewelers published the first standardised birthstone list in 1912. Tourmaline was added as an alternative in 1952 by the Jewelry Industry Council of America, providing a more durable option for rings intended for daily wear.
Birthstone traditions predate the modern lists by centuries. The connection between specific gemstones and calendar months draws from several historical sources, including the twelve stones set in the biblical High Priest's breastplate, though assignments shifted considerably before the 1912 standardisation brought consistency to the jewellery trade. When tourmaline was introduced forty years later, it offered greater hardness — 7 to 7.5 on the Mohs scale compared to opal's 6 — making it better suited to rings intended for daily wear. Both stones remain equally recognised as official October birthstones.
| Property | Opal | Tourmaline |
|---|---|---|
| Mohs Hardness | 6 | 7–7.5 |
| Chemical Composition | SiO₂·nH₂O (hydrated silica) | Complex borosilicate |
| Crystal System | Amorphous | Trigonal |
| Key Optical Effect | Play of colour | Pleochroism |
| Primary Historical Source | Hungary (now Slovakia) | Ceylon (now Sri Lanka) |
What Is Opal?
Opal is a hydrated form of silica (SiO₂·nH₂O) containing between 4 and 10 per cent water. Unlike most gemstones, it has no crystalline structure — it is amorphous, formed from microscopic spheres of silica deposited as a gel that solidified over millions of years. This unusual structure produces opal's distinctive optical behaviour.
Precious opal displays play of colour: flashes of spectral light that shift as the stone moves. The silica spheres, ranging from approximately 150 to 300 nanometres in diameter, stack in regular arrays. When white light passes through these arrays, it diffracts into its component wavelengths — red, green, blue, orange, and violet — depending on sphere size and viewing angle. The Romans prized opal above nearly all other gemstones. Pliny the Elder, writing in his Natural History around 77 AD, described it as combining the fire of ruby, the purple of amethyst, and the sea-green of emerald.
Why Were Opals Once Considered Unlucky?
The superstition that opals bring bad luck stems primarily from Sir Walter Scott's 1829 novel Anne of Geierstein, in which a character's enchanted opal talisman loses its colour when touched by holy water, and the wearer dies shortly afterward. The novel's popularity caused opal sales across Europe to drop by roughly half, and the stigma persisted for decades.
Before Scott's novel, opals carried strongly positive associations — the Romans considered them symbols of hope and purity. The reversal of the opal's reputation after 1829 became one of the most striking examples of literature directly affecting a gemstone market. Queen Victoria played a direct role in restoring the stone's standing. An avid collector of opals, she wore them publicly and gave opal jewellery as gifts to her five daughters and members of her court. When the Queen endorsed a gemstone, the superstition around it became difficult to sustain.
How Did Victorian Jewellers Use Opals?
Victorian jewellers typically set opals in 18ct or 15ct yellow gold, using collet settings that cradled each stone securely. Three-stone arrangements with an opal flanked by diamonds became a popular format, with the diamonds providing contrast that emphasised the opal's play of colour and adding structural protection to the softer central stone.
The discovery of opal in South Australia during the 1840s, followed by commercial production from Queensland and New South Wales through the 1870s and 1880s, transformed the available supply. Australian opal offered stronger play of colour and larger stones than traditional Hungarian material, and by the 1890s Australia produced the majority of the world's gem-quality opal. Victorian opal rings almost always feature cabochon-cut stones — the domed surface maximises the display of play of colour across the widest viewing area. Settings from this period often include scrollwork galleries beneath the stones and carved or moulded claw mounts that protect the relatively soft opal from impact.
Browse our collection of antique opal rings to see Victorian and Edwardian examples with original settings. For a complete history of opals in antique jewellery, read Opals: Fire, Superstition & the Victorian Revival.
What Types of Opal Appear in Antique Rings?
White opal — translucent with a pale body colour and pastel play of colour — is the most common variety in antique rings. Black opal, with its dark body tone that makes spectral flashes appear more vivid, commands the highest prices of any opal variety. Fire opal, a transparent orange to red stone from Mexico, appears less frequently in British antique jewellery.
| Opal Type | Body Colour | Play of Colour | Primary Source |
|---|---|---|---|
| White opal | White to light grey | Pastel flashes | South Australia |
| Black opal | Dark grey to black | Vivid, high-contrast | Lightning Ridge, NSW |
| Boulder opal | Brown ironstone matrix | Bright, within host rock | Queensland |
| Fire opal | Orange to red, transparent | Variable, often absent | Querétaro, Mexico |
| Crystal opal | Transparent to semi-transparent | Visible through body | Various |
In antique jewellery, white opal predominates because Australian black opal — first found at Lightning Ridge in the 1870s with commercial mining beginning in the 1890s — did not reach the market in significant quantities until the early twentieth century. Most Victorian opal rings therefore feature white or crystal opal sourced from Hungarian deposits or early Australian fields. The dark body colour of black opal acts as a backdrop that intensifies spectral flashes, making red-on-black the most sought-after combination.
What Is Tourmaline?
Tourmaline is a complex borosilicate mineral that occurs in more colours than any other gemstone species. Its name derives from the Sinhalese turamali, meaning mixed gems — a term applied to multicoloured pebbles found in the gem gravels of Ceylon. Dutch traders in the early eighteenth century brought these stones to Europe, initially confusing them with other minerals.
Tourmaline was not formally recognised as a distinct mineral species until 1793. Before that, specimens were routinely misidentified — a Spanish conquistador in sixteenth-century Brazil mistook green tourmaline for emerald, a confusion that lasted nearly three hundred years. In the late nineteenth century, the American gemmologist George F. Kunz, working for Tiffany & Co., championed tourmaline deposits in Maine and California, helping to establish the stone's identity in the jewellery trade. Tourmaline rates 7 to 7.5 on the Mohs hardness scale and exhibits two unusual physical properties: pyroelectricity (generating an electrical charge when heated) and piezoelectricity (generating a charge under pressure).
| Tourmaline Variety | Colour | Notes |
|---|---|---|
| Rubellite | Pink to red | Most valued in antique settings |
| Indicolite | Blue to blue-green | Rarer variety |
| Verdelite | Green | Historically confused with emerald |
| Watermelon | Pink centre, green rim | Bi-colour cross-sections |
| Paraíba | Neon blue-green | Discovered 1989 in Brazil |
How Should You Care for an Opal Ring?
Opal requires more careful handling than most gemstones because of its water content and relative softness. Store opal rings separately from harder stones to prevent scratching, avoid sudden temperature changes that can cause crazing — fine surface cracks from moisture loss — and remove opal jewellery before tasks involving chemicals, detergents, or physical impact.
Clean opal with lukewarm water and a soft cloth. Avoid ultrasonic cleaners, steam cleaners, and chemical solutions. Tourmaline is more straightforward to maintain — its greater hardness and absence of water content mean it tolerates everyday wear with fewer precautions. Warm soapy water and a soft brush are sufficient. When choosing between the two October birthstones for a ring worn daily, tourmaline offers greater practicality. Opal suits pieces worn with care — dress rings, occasional wear, or carefully maintained everyday rings.
Explore our Victorian ring collection for antique pieces from the era when opal jewellery reached its peak popularity.
Frequently Asked Questions
Is opal too fragile for an engagement ring?
Opal rates 6 on the Mohs hardness scale, lower than sapphire or diamond, and its water content makes it sensitive to temperature changes. Many people wear opal engagement rings successfully, but the stone requires more care than harder alternatives. A protective bezel or collet setting reduces exposure to knocks. For a ring worn daily in all conditions, tourmaline is the more durable October birthstone choice.
Can opal lose its play of colour over time?
Opal can lose play of colour through a process called crazing, where fine surface cracks develop as the stone loses internal moisture from prolonged heat exposure or very dry storage. Well-maintained opals retain their play of colour indefinitely — museum opals hundreds of years old still display vivid spectral colour. Proper storage away from direct heat and sunlight preserves the effect.
What is the most valuable type of opal?
Black opal from Lightning Ridge in New South Wales commands the highest prices. The dark body colour intensifies the spectral play of colour, with red-on-black combinations valued most highly. At auction, exceptional black opals have exceeded per-carat prices of many other gemstones. Among antique pieces, well-preserved Victorian opals with strong play of colour and original settings carry both gemmological and historical value.
How can you tell opal from tourmaline?
The two stones look nothing alike. Opal displays a shifting play of spectral colour across a translucent or opaque body — no other gemstone produces this effect in the same way. Tourmaline is a transparent, faceted stone typically appearing in a single colour. Opal is almost always cut as a cabochon with a domed surface; tourmaline is conventionally faceted. The distinction is visible at a glance.
Are antique opal rings a sound purchase?
Quality antique opal rings have appreciated in value, driven by finite supply — every antique piece sold is one fewer available. Black opals in particular have seen strong price growth. Prioritise stones with vivid play of colour, original settings, and verifiable age through hallmarks or documented provenance. A ring from the Victorian or Edwardian period with intact opals and clear hallmarks represents both a wearable piece and a collectible asset.
What setting best protects an opal in a ring?
A bezel or rubover setting — where a rim of metal encircles the stone's perimeter — offers the greatest protection for opal. Claw settings leave the stone more exposed to knocks but allow more light to reach the opal, enhancing play of colour. Victorian jewellers frequently used collet settings: individual metal cups that held each opal securely while leaving the face of the stone fully visible.
Related Reading
- Opals: Fire, Superstition & the Victorian Revival — the complete history of opals in antique jewellery
- September Birthstone: Sapphire — the preceding month's birthstone guide
- Victorian Rings: Romance, Mourning & Empire — the era when opals returned to fashion
- Read our complete guide to gemstones in antique rings — the Gemstones pillar page