October Birthstone: Opal vs Tourmaline

By Lisa Chen, Founder · July 12, 2026

Short answer: October has two birthstones, opal and tourmaline, and the honest difference between them is durability. Opal is soft and sensitive to water and heat, so a lot of what sells as opal is treated, assembled, or lab-grown. Tourmaline is harder and far easier to live in day to day. This guide covers what each stone is, what the labels mean, and how to choose for how you wear jewelry.

Why October gets two birthstones

Most months have one birthstone; October has two, for a plain reason. The month-by-month list American jewelers use is a twentieth-century trade convention, not an ancient law. The modern list was standardized by the American jewelry trade in 1912, with opal as October's stone; pink tourmaline was added in a 1952 update. The American Gem Society and the Gemological Institute of America both recognize both today.

That history is the honest frame for what a birthstone "means." Older folklore tied opal to hope and tourmaline to protection; it is charming, but it is culture, not chemistry. A birthstone will not change your luck, your health, or your love life, whatever a seller implies. The useful question is which stone suits your life.

Opal, honestly

Opal is hydrated silica: the same basic silica as quartz, but with no crystal structure and water locked inside, commonly from a few percent up to roughly a fifth of its weight. That water is the source of both its magic and its fragility. In precious opal, ordered silica spheres bend light into a shifting play of color; common opal, or potch, has the color without the fire.

The catch is hardness. Opal measures 5.5 to 6.5 on the Mohs scale, according to the U.S. Geological Survey's hardness reference. Everyday dust and grit contain quartz, which sits at 7, so ordinary handling can slowly scuff an exposed opal over the years. Opal is also porous and, in GIA's words, generally stable, but heat from intense light can cause fracture lines called crazing, and a sudden temperature change can do the same. That is why an opal can craze if it dries out or meets hot water.

Because natural, durable opal is expensive, much of what you will see is one of the following, and a good seller will tell you which:

• Treated opal. GIA notes opal is often impregnated or coated with oil, plastic, or wax, and smoke or sugar-acid treatments deepen the body color. Normal practice, but it needs disclosing and rules out cleaning machines.
• Doublets and triplets. A doublet is a thin slice of opal glued to a dark backing; a triplet adds a clear protective cap. Both use thin, beautiful opal affordably, but they are assembled stones, and the glue fails if you soak them.
• Lab-created opal. Synthetic opal (Gilson-type material is the classic example) is real opal grown in a lab, often with a very regular pattern. A fair, lower-cost option when labeled lab-created, and not a natural stone.
• Imitation opal. Plastic or glass "opalite" mimics the look for very little. Fine for costume pieces, but it is not opal and should never be priced as if it were.

Tourmaline, honestly

Tourmaline is the easier stone to live with. It is not a single mineral but a boron silicate group whose trace elements produce more colors than almost any other gem, which is why the trade nicknames it the rainbow stone. You will meet it under variety names: rubellite for red and pink, indicolite for blue, chrome and verdelite for green, the prized copper-bearing Paraiba for electric blue-green, and watermelon tourmaline, pink in the center and green at the rim.

On durability, tourmaline measures 7 to 7.5 on the Mohs scale per the USGS reference, a full point or more above opal and at or above everyday quartz dust. It is not indestructible, but it holds up to normal wear far better, which is what you want in a stone you plan to actually use.

Tourmaline has its own disclosure worth knowing: color enhancement. GIA lists heating and irradiation as its two most important treatments, and the resulting color is stable and undetectable. So much of the vivid tourmaline you see has been helped along; that is accepted practice, and it holds its color. One caution: tourmaline often carries liquid inclusions, and heavily included stones dislike heat, which is why the care rules below matter.

Opal vs tourmaline at a glance

Here is the honest side-by-side. Every hardness figure is from the USGS Mohs reference.

	Opal	Tourmaline
Mohs hardness	5.5–6.5	7–7.5
What it is	Hydrated silica, no crystal structure, holds water	Boron silicate mineral group
Water and heat	Sensitive; can craze from heat, light, drying, or thermal shock	Stable to light and chemicals; heavy inclusions dislike heat
Common trade forms	Natural, treated, doublet or triplet, lab-created, imitation	Natural, commonly heat-treated or irradiated for color
Everyday wearability	Best for pendants, earrings, occasional wear	Comfortable for daily wear, including rings

• The hardness row is the decision. A point on the Mohs scale is a large jump in scratch resistance, which is why jewelers steer hands-on wearers toward tourmaline.
• The trade-forms row is where questions pay off. With opal, confirm natural versus treated versus assembled versus lab; with tourmaline, mostly confirm the color treatment.

How to choose for your lifestyle

Start with your hands, not the stone. A ring you wear every day and garden in is a job for tourmaline; it shrugs off the contact that would slowly frost an opal. A pendant or earrings that live above the fray make opal completely reasonable, and unmatched for that living flash of color.

• Daily ring or bracelet. Tourmaline, or set an opal in a protected bezel mount and accept that it needs care.
• Necklace or earrings. Either works. This is where opal shines, because it takes far fewer knocks.
• Budget-conscious but honest. Lab-created opal or a well-made opal triplet gives the look for less, as long as it is labeled for what it is.
• You want one stone that simply lasts. Tourmaline, every time.

Buying October birthstone jewelry honestly

Two things decide whether an October piece is a fair buy: the stone and the metal. On the stone, ask the seller to say plainly whether it is natural, treated, assembled as a doublet or triplet, lab-created, or imitation. Any of those can be a good buy at the right price; the only wrong answer is a vague one. Be wary of a very cheap opal or tourmaline, because colored cubic zirconia or glass often stands in for a real stone at rock-bottom prices, and cubic zirconia is a diamond simulant, not a gemstone in its own right.

Read the metal the same way. At the affordable end, "18k gold" almost always means 18k gold plating over a base metal such as stainless steel or brass, not solid gold. That is true of my own pieces at Stylr: our gold is a genuine 18k plating over a steel or brass core, and I would rather say so than let anyone assume solid gold. If sensitive skin is your concern, 316L stainless steel is a good, low-nickel setting, but it is low nickel rather than truly nickel-free, so I never call it that. Honest labels on the stone and the metal are the whole game.

If you would rather skip the guesswork, our everyday necklaces are gold-plated stainless steel built to survive real life, water, sweat, and daily wear, the same durability logic that makes tourmaline the easy October pick.

Caring for opal and tourmaline

• Opal. Clean it with warm, soapy water and a soft cloth only. GIA is blunt that opal should never go in an ultrasonic or steam cleaner, both for the heat and because so much opal is treated. Keep it from sudden temperature changes and dry heat, and if it is a doublet or triplet, do not soak it, since water breaks down the glue and clouds the stone.
• Tourmaline. Warm, soapy water is again the safe method, and GIA advises against ultrasonic and steam cleaning here too, because tourmaline's liquid inclusions dislike heat. Store it so harder stones cannot scratch it, and take rings off before heavy tasks.
• Both. Put jewelry on last, after lotion, perfume, and hairspray, and take it off first. That one habit prevents most of the dulling people blame on the stone itself.

Frequently asked questions

What is October's birthstone?

October has two: opal and tourmaline. Opal is the older choice on the modern American birthstone list standardized in 1912; pink tourmaline was added in a 1952 update. Both are recognized by the Gemological Institute of America and the American Gem Society today.

Which October birthstone is better for everyday wear?

Tourmaline, usually. It measures 7 to 7.5 on the Mohs scale versus opal's 5.5 to 6.5, per the U.S. Geological Survey, so it is much more scratch-resistant. That matters most for rings and bracelets; opal is better suited to pendants and earrings, or to a protected setting.

Is most opal jewelry treated or lab-created?

A large share is, and that is fine when disclosed. Opal is commonly treated by impregnation or coating, assembled into doublets and triplets, or grown in a lab as synthetic opal. Ask the seller which one you are buying, and treat a suspiciously cheap opal as possibly imitation glass or plastic.

Can I wear opal in the shower or the pool?

Better not to. Opal is porous and, as GIA notes, can craze from heat, intense light, or a sudden temperature change, so hot water and thermal shock are real risks. Doublets and triplets are worse, because soaking dissolves the glue between the layers. A solid opal pendant tolerates the odd splash, but do not make a habit of it.

Is tourmaline heat-treated?

Often, yes. GIA lists heating and irradiation as tourmaline's two most important treatments, and the resulting color is stable and hard to detect, so most vivid tourmaline has likely been enhanced. It does not weaken the stone; just ask the seller to confirm the treatment.

The short version is the one I opened with: pick opal for its living color and give it gentle habits, or pick tourmaline when you want a stone that keeps up with daily life. Either way, the honest details, natural versus treated and plated versus solid, are what protect your money. For more, see our December birthstone guide on turquoise and its own softness, and our June birthstone guide on pearl and moonstone. When you are ready to shop a piece you can actually wear, our everyday rings follow the same survive-real-life standard.

If you want to wear October’s stone rather than read about it, our Personalized Cross & Birthstone Necklace is made in a October version — 18k gold plating over a 316L stainless steel base, built for daily wear. The stones are cubic zirconia, not mined gems, and the product page says so.