The October birthstone opal is the one gem that behaves like weather. Tilt it and the color moves, which is why people have written about opals for two thousand years in language they usually reserve for skies and water. Opal has stood for hope, faithfulness and truth, and it also carries a superstition about bad luck that turns out to have a traceable and fairly recent source. Here is what opal is, what it has meant, how to choose an October birthday gift, and why this particular stone needs looking after more carefully than most.

What opal is, and why the color moves

Most gemstones are crystals. Opal is not. It is hydrated silica, laid down as microscopic spheres in a jelly like solution that slowly dried inside cracks and cavities in rock, and it holds water: commonly between three and ten percent, sometimes more.

The play of color that makes precious opal famous comes from those spheres. When they are uniform in size and stacked in an orderly grid, they diffract light in the same way a grating does, splitting it into moving flashes of spectral color. Small spheres produce blues and violets; larger spheres produce reds and oranges, which is why red flash opals are the rarest and most valuable. Opal without this ordered structure is called common opal, or potch, and shows no play of color at all.

The main varieties are worth knowing. Black opal, mostly from Lightning Ridge in New South Wales, has a dark body color that makes the flashes look electric. White or milky opal, associated with Coober Pedy in South Australia, is paler and more common. Boulder opal from Queensland is cut with its ironstone host still attached. Fire opal from Mexico is prized for a warm orange body color rather than for flash.

Ethiopian opal, mined more recently, behaves differently: much of it is hydrophane, meaning it absorbs water and can temporarily go cloudy or transparent when wet. That is not damage, but it is a reason to keep Ethiopian material away from water entirely.

Hardness is 5.5 to 6.5 on the Mohs scale, which is soft, and opal has no cleavage but is prone to crazing, a network of fine cracks that can develop if a stone dries out or takes a sharp temperature change.

What the October birthstone opal symbolizes, and the bad luck myth

Classical writers treated opal as the most remarkable of gems precisely because it seemed to contain all the others. Pliny the Elder described it as holding the fire of ruby, the purple of amethyst and the green of emerald at once. From that came its traditional meanings: hope, purity, truth and faithfulness, along with a long association with clear sight.

The superstition that opals bring bad luck is much younger than the stone's reputation, and its popularity can be traced to a novel. Walter Scott published Anne of Geierstein in 1829, in which a character wears an opal that loses its fire and whose fortunes collapse. The book was widely read, and opal sales across Europe are said to have fallen sharply afterwards. Nothing in the stone's earlier history supports the idea.

What probably kept the superstition alive is the stone's fragility. Opal chips, crazes and dries more readily than the gems around it, so jewelers historically had more accidents with it, and a gem that broke in a customer's hands did not need help to acquire an unlucky reputation.

For an October birthday, the honest framing is the older one. This is the stone of faithfulness and of hope, and it looks different from every angle, which makes it a natural gift for someone whose depth is not obvious at first glance.

Choosing an October birthstone opal gift

Opal's association with faithfulness gives an October gift a theme that suits family, long friendships and belief far better than it suits romance.

For someone whose faith is central

The Lord Your God Will Be With You cross necklace is written for a person facing something specific rather than for general devotion, which is what separates a gift from a greeting. For a daughter, the Be Strong faith cross necklace pairs the same idea with wording aimed at someone younger. The full faith cross necklace range covers the same ground in several pendant styles.

For a hard season rather than a celebration

The Every Day May Not Be Good cross necklace is the rare gift that admits things are difficult instead of insisting they are fine. That honesty is why it works for illness, grief or a long stretch of bad news, where cheerful gifts land badly. Browse the wider spiritual gift range for pieces in the same register.

If you want the stone itself

Opal is beautiful and demanding. Choose a pendant or earrings over a ring, because a ring takes the knocks that opal cannot. Check our birthstone necklaces for the stone options each listing offers, and read the care section below before you buy for someone who will wear it daily.

What to write for an October birthday

Opal gives you an easy and overused metaphor: many sided, different in every light. Use it once, if at all, and spend the rest of the card on the person.

If the gift marks faithfulness, name the duration and the proof. "Eleven years, and you have never once made me feel like a burden" does more than any adjective. Faithfulness is invisible by nature, so saying you noticed it is most of the gift.

If the gift is going to someone in a difficult season, do not write about brightness or silver linings. Write that you are still here, that you are not going anywhere, and what specifically you will do this month. A concrete offer beats an abstract promise.

Keep it short and sign it by hand. The printed card sets the theme; your handwriting proves the thought.

How to care for opal, which needs more protection than most gems

Opal contains water, and that single fact drives every care rule. Sudden temperature changes can crack it. Long periods in very dry air can dry it out and craze it. Neither happens quickly, but both are permanent.

Never use an ultrasonic or steam cleaner on opal. Clean it with a soft, slightly damp cloth and nothing else. Avoid soaking it, and with Ethiopian hydrophane material avoid water altogether, since the stone can absorb it and go cloudy for days.

Take opal jewelry off before sport, cleaning and anything involving impact. At 5.5 to 6.5 on the Mohs scale it is softer than the quartz dust in ordinary household grit, which means everyday abrasion alone will dull an unprotected stone over the years.

Store it away from harder stones, ideally in a soft pouch inside a box rather than loose in a tray. Keep the printed card from a gift flat and dry in the same place. Our jewelry care tips cover storage and cleaning for the sturdier pieces in the same box.

When to give it

October sits in a useful gap. The summer is over, the December rush has not started, and a birthday in it gets full attention from everyone you would want to invite.

If the gift is about faith or about standing by someone, the birthday is not necessarily the best moment for it. The night before a diagnosis, the first anniversary of a loss, the week someone moves into care: those days are when a gift about faithfulness actually does something.

Give it privately if the card is personal. Something written about staying is not easy to read in a room full of people, and the reading is the part that matters.

Questions buyers ask

Are opals really bad luck?

No. The superstition is usually traced to Walter Scott's 1829 novel Anne of Geierstein, in which an opal features in a character's downfall. Before that the stone had a long reputation for hope and faithfulness, and the myth probably persisted because opal is fragile and broke more often than other gems.

Why does opal sometimes crack or craze?

Opal contains water, so sudden temperature changes and very dry conditions can produce a network of fine cracks called crazing. Keep opal away from heat, direct sun for long periods and ultrasonic cleaners, and never store it somewhere hot and airless.

Can opal be worn every day?

A pendant or earrings can be, with care. A ring is a poor choice, because at 5.5 to 6.5 on the Mohs scale opal is softer than everyday grit and vulnerable to knocks. Take it off for sport and housework.

What is the other October birthstone?

Tourmaline. October is one of the months with two, so if opal feels too delicate for the person you are buying for, a tourmaline in almost any color is an equally correct choice.