birthstones · October
Opal
October's bottled aurora · Also for this month: tourmaline
October wears every colour at once: opal, hydrated silica that diffracts light into shifting fire. Its file: imagination, inspiration, all-of-the-above — plus the most famous curse rumour in gemology, debunked below.
Story & folklore
Rome called it opalus and prized it as containing every gem's virtue; Arabic lore said opals fell in lightning. The 'unlucky' rumour is traceable: an 1829 Walter Scott novel featured a fateful opal, sales dipped, jewellers grumbled for a century — a literary review mistaken for a curse.
The honest paragraph
October's stone carries this list's cleanest debunk: the bad luck is fan fiction with a publication date. The play-of-colour is diffraction through silica spheres — real, mesmerising physics. Care is the true caution: opals hold water (5-10%) and dislike heat, dryness and knocks; the drama was always in the mineral, never the luck.
The cat's eye catches the lamp and flashes every colour: "Curses. Inventions of the unimaginative."
Birthstone meanings are tradition and story, told with affection — a lovely lens for a gift or a self-portrait, never a verdict or a promise.
Opal history: from Roman treasure to Australian fields
The opals prized in Roman times came mainly from deposits in what is now Slovakia, then part of the Hungarian kingdom. In the late 19th century Australia’s opal fields opened (Lightning Ridge, Coober Pedy, Queensland’s boulder fields), and Australia became the dominant source of precious opal, which it still is. Ethiopia’s Welo deposits, found in the late 2000s, added bright, affordable opal to the market. Queen Victoria was a well-known admirer who gave opal jewellery to her daughters, which helped counter the 19th-century superstition described above.
Opal types and colours
- White or light opal: a milky body with pastel play-of-colour. It’s the most common.
- Black opal: a dark body that makes the colours blaze. It’s the most valuable, famous from Lightning Ridge.
- Boulder opal: thin seams of opal in ironstone, often cut with the brown host rock left on the back.
- Crystal opal: transparent to translucent, with colour that seems to float inside.
- Fire opal: orange to red transparent opal, mainly from Mexico, sometimes without any play-of-colour.
- Ethiopian Welo opal: often bright and affordable, but hydrophane, meaning it absorbs water.
How to choose a real opal and spot imitations
- Doublets and triplets: a thin slice of real opal glued to a dark backing (doublet), sometimes with a clear quartz or glass cap (triplet). They’re affordable and legitimate if disclosed. Look at the side for a straight join line, and never soak them.
- Synthetic (lab-created) opal: often shows a regular “snakeskin” or columnar pattern under magnification.
- Imitations: plastic and glass. The glass sold as “opalite” shows only a soft blue-orange glow and no real play-of-colour.
- Real play-of-colour shifts as you tilt the stone. Patches appear and disappear, not just one uniform shimmer.
- For Ethiopian opal, ask whether it’s been “smoked” or dyed to darken it.
Opal care, gifts and symbolism
Opal is about 5.5 to 6.5 on the Mohs scale, softer than most gems, and sensitive to knocks, heat and sudden temperature changes, which can cause crazing (fine cracks). Clean it only with a soft damp cloth and mild soap. Never use ultrasonic or steam cleaning, and never soak doublets or triplets. Keep hydrophane Ethiopian opal away from oils and lotions, which it can absorb.
Gift ideas include an opal pendant or earrings for an October birthday, a protected bezel-set ring for occasional wear or a boulder opal slice as a unique pendant. In the symbolic tradition opal stands for imagination, hope and creativity. October’s flower is the marigold, and its alternative stone is tourmaline. For a calm companion crystal, see labradorite.