October Birthstone
October gets two birthstones, and they solve opposite problems. Opal — the traditional stone — is unlike anything else in the mineral world: a hardened silica gel that diffracts light into shifting patches of spectral color, so no two stones are alike and no photograph does one justice. Pink tourmaline — the modern addition — is its practical counterpart: a durable, transparent crystal in pinks from petal-pale to hot magenta.
This page covers both stones properly: what opal actually is (and why it plays with light), what makes tourmaline the most color-rich crystal family in gemology, which color counts as "the October color," how the month ended up with two stones, and what to check before buying either.
The October birthstones
Hydrated amorphous silica — not a crystal at all, but hardened silica gel containing up to 20% water, built from microscopic spheres. When those spheres are uniform in size and neatly stacked, they diffract light into play-of-color: shifting patches of green, blue, orange and red that move as the stone turns. Precious opal with play-of-color is the celebrated form; common opal (without it) comes in soft pastel body colors. At 5.5 to 6.5 on the Mohs scale and water-bearing, opal is a handle-with-care gem.
The pink-to-red range of elbaite, the gem species of the tourmaline family — a boron silicate whose flexible chemistry produces more colors than any other gem mineral. Pink and red tourmalines owe their color mostly to manganese; vivid reds are traded as rubellite. Tourmaline crystals are three-sided prisms with lengthwise striations, often color-zoned (the famous "watermelon" slices are pink cores in green rinds). At 7 to 7.5 on the Mohs scale it is comfortably an everyday-jewelry stone — the durable October choice.
What color is the October birthstone?
October has no single birthstone color — and that is the honest answer. Opal's signature is not a color but an effect: a white, black or crystal body flashing every color of the spectrum at once. Pink tourmaline contributes the month's one nameable hue, so charts, birthstone jewelry and "October color" lists usually settle on pink — with multicolor or opalescent white as the alternative way to represent the month.
If you need to pick one for a gift or a chart: pink is the safe conventional answer for October; a white opal cabochon is the traditional one. Black opal — dark-bodied with fire on it — is the connoisseur's version of the same birthstone, and the most valuable form of opal there is.
How October got its birthstones
Opal's reputation has swung harder than any other birthstone's. Roman writers ranked it above all gems because it seemed to hold every color at once; medieval Europe considered it lucky; then a 19th-century superstition — fed partly by Sir Walter Scott's 1829 novel Anne of Geierstein, in which an opal loses its fire when touched by holy water — branded it unlucky for anyone not born in October. The stigma was commercially convenient nonsense, but it stuck for decades and still echoes in the "is opal bad luck?" question.
When the US list was standardized in 1912, October's stone was opal; tourmaline was added in the 1952 revision, giving buyers a transparent, durable alternative. Most of the world's precious opal has come from the fields of South Australia — Coober Pedy above all — with Ethiopia's Wollo deposit joining as a major source after 2008.
Choosing & caring for October birthstones
Opal rewards caution: solid natural opal is the thing to ask for, because much cheap "opal" jewelry is a doublet or triplet — a paper-thin opal slice glued to a dark backing and often capped with clear quartz. Viewed from the side, a glued seam gives these away. Synthetic opal (regular, snakeskin-like color patches) is also common. Keep opal away from prolonged heat and knocks, and never soak doublets. Pink tourmaline needs no special care beyond avoiding hard blows; check for eye-visible inclusions, which are common in pinks, and for color zoning face-up.
Frequently asked questions
What are the October birthstones?
Two stones share October: opal, the traditional birthstone on the list since 1912, and pink tourmaline, added in the 1952 revision. Either one — or both together — is correct for an October birthday.
What color is the October birthstone?
Convention says pink, from pink tourmaline — but opal's play-of-color means October is really the multicolor month. Charts and jewelry use either a pink stone or a white opalescent one to stand for October.
Is opal bad luck if you weren't born in October?
No. The superstition is a 19th-century invention — popularized after an 1829 Walter Scott novel and kept alive by rival gem traders — with no older tradition behind it. Romans considered opal the luckiest of gems. Wear it in any month.
Why does opal change colors?
It doesn't change color so much as diffract light. Opal is built of microscopic silica spheres; where the spheres are even-sized and orderly, they split white light into pure spectral patches that shift as the viewing angle changes — play-of-color. Sphere size sets which colors appear: smaller spheres give blues and greens, larger ones add rare reds.
How can I tell real opal from synthetic or a doublet?
Look from the side for a flat glue line (doublet/triplet), and study the color patches: synthetic opal often shows suspiciously regular, columnar 'lizard-skin' patches, while natural play-of-color is irregular. A photo through our identifier plus the opal field guide's checks will sort most cases; high-value stones deserve a gemologist's verdict.
See the full birthstones-by-month chart or jump to August, December, June.
Last updated 2026-07-18