October's Two Birthstones: Opal or Tourmaline, and Which to Buy
October birthdays get two birthstones, and the two could hardly be less alike. One is soft and does something with light that no other gem manages. The other is hard enough for daily wear and comes in almost every colour you can name. Picking between them comes down to what you plan to put the stone in and how the person wears their jewellery. Here is how we talk it through at the counter.
Why October has two stones
Opal is the older of the two. GIA calls opal the traditional October birthstone and traces the name to India, where in Sanskrit it was upala, a precious stone. Tourmaline is the newer one. Its name comes from the Sinhalese toramalli, stone with mixed colours, because a single crystal often carries several.
Our reading of why a second stone was added is supply. Fine opal with strong play-of-colour has never been common, it is difficult to cut, and it is soft enough that setting it in a ring takes thought. Tourmaline fixed that. It is mined in quantity, it comes in every hue, and it holds up to being worn.
What makes an opal flash
GIA describes precious opal as sub-microscopic spheres stacked in a grid-like pattern, like layers of Ping-Pong balls in a box. Light passing between the spheres bends, or diffracts, and splits into the colours of the rainbow. That is play-of-colour, a structural effect rather than a pigment. Change the sphere size and you change which colours appear, which is why red flashes cost more than blue ones.
GIA splits opal into two classes on exactly this point. Precious opal shows play-of-colour. Common opal does not, and the price should reflect that.
The opal types you will actually be shown
GIA's description page lists five main types. White or light opal has a pale body colour. Black opal has a dark body colour, which makes the flashes read brighter by contrast, and the famous source is Lightning Ridge in New South Wales. Fire opal is orange to red bodied, often from Mexico, and may show no play-of-colour. Boulder opal keeps a layer of host ironstone attached. Crystal opal is transparent to semitransparent with a clear background.
Then there are assembled stones, and this is where buyers get caught. GIA defines a doublet as a thin layer of opal cemented to a backing of obsidian, dyed black chalcedony, black glass, common opal or plastic. A triplet adds a domed top of colourless quartz or clear glass. Both sell for a fraction of solid opal.
Look at the side of the stone. A doublet or triplet shows a flat join line. A solid opal shows colour through the edge. Ask, and get the answer on your receipt.
Water, heat and the crazing problem
GIA warns that prolonged exposure to water may weaken the adhesive in opal doublets and triplets. That is the rule we repeat most often in the shop. A soaked triplet goes cloudy from the inside as water works between the layers, and the play-of-colour vanishes behind a grey film.
Solid opal has a different weakness. GIA states that heat from intense light can cause fracture lines called crazing, and that high heat or sudden temperature change can also fracture opal. So an opal stays off sunny windowsills, out of hot cars, and out of hot dishwater.
Tourmaline: one mineral group, nearly every colour
GIA describes tourmalines as a group of closely related mineral species that share the same crystal structure but have different chemical and physical properties, sharing silicon, aluminium and boron while mixing in sodium, lithium, calcium, magnesium, manganese, iron and chromium. That chemistry is why GIA says tourmaline has one of the widest colour ranges of any gem species, occurring in shades of virtually every hue.
Several colours carry trade names. Rubellite covers pink through red. Chrome tourmaline is the deep green that can resemble emerald. Indicolite is the blue. Watermelon tourmaline is pink in the centre and green around the outside, and GIA notes those crystals are typically cut in slices to display the arrangement, zoning GIA attributes to trace elements changing as the crystal grew. At the top sits Paraiba, which GIA describes as an intense violetish blue, greenish blue or blue tourmaline from Paraiba state in Brazil, coloured by copper, with a fine one's per-carat price likely to rival fine sapphire.
| Property | Opal | Tourmaline |
|---|---|---|
| Mohs hardness | 5 to 6.5 | 7 to 7.5 |
| Toughness (GIA) | Poor to fair, at the bottom of GIA's scale | Fair |
| Everyday wear | Needs care so the stone is not scratched or broken | GIA calls it generally suitable for everyday wear |
| Main weakness | Crazing from heat or intense light; sudden temperature change | High heat can alter colour; thermal shock can fracture |
| Ultrasonic and steam | Warm soapy water is the only safe method | Not recommended |
| Storage | Store alone; diamond, ruby, sapphire and emerald will scratch it | Store apart from diamond and corundum |
| Best setting type | Bezel or half-bezel, raised edge | Prong or bezel, both work |
Ring or pendant: how we decide
A ring lives on a hand that opens doors, carries bags and gets washed a dozen times a day. That punishes a stone GIA places at 5 to 6.5 with toughness at the bottom of its scale. Tourmaline at 7 to 7.5 handles it. For an October birthday ring meant to be worn without thinking, tourmaline is our recommendation, in whatever colour the wearer likes.
A pendant changes the maths completely. It hangs clear of impact, it sits at chest height where play-of-colour is seen straight on, and it spends most of its life against fabric. That is the right home for a solid opal. Our own pick for an October gift is a solid opal pendant in 14K with a bezel, which protects the vulnerable edge of the stone. Our necklace length guide helps with picking a chain.
Earrings lean toward opal too, since ears take few knocks. The one thing we will not do is set an opal in a ring for someone who works with their hands, because we would be selling a repair bill. For the wider comparison, we wrote about gemstone hardness and what the Mohs number predicts, and our opal care guide covers day-to-day handling.
What to ask before you pay
For opal, three questions. Is it solid, a doublet or a triplet? Where is it from, since Australian, Ethiopian and Mexican material behave differently in water? Has it been treated by impregnation with oil, wax or plastic, or by sugar or smoke treatment, all of which GIA lists as opal treatments?
For tourmaline, ask whether the stone has been heated or irradiated. GIA notes that heat treatment results are permanent, and that colour produced by irradiation can fade with exposure to heat or bright light. An irradiated stone is fine to buy when it is disclosed and priced as such. It should not sit in a sunny window.
October birthstone pendants
A few pendants from our cases in Coquitlam. If you want a specific opal or tourmaline colour set into one of these, we make pieces on our own bench.
Key Takeaways
- GIA rates opal 5 to 6.5 on the Mohs scale with toughness at the bottom of its scale, while tourmaline is 7 to 7.5 and generally suitable for everyday wear.
- Play-of-colour comes from sub-microscopic silica spheres diffracting light, so an opal with no flashes is common opal and should be priced as such.
- Never soak a doublet or triplet. GIA warns that prolonged water exposure weakens the adhesive holding the layers together.
- Warm soapy water is the only safe cleaning method for opal, and GIA does not recommend ultrasonic or steam cleaners for tourmaline either.
- For a ring worn daily, buy tourmaline. For a pendant or earrings, opal earns its place in a bezel that shields the edge.
Frequently Asked Questions
Why does October have two birthstones instead of one?
Opal came first. GIA calls opal the traditional October birthstone and tourmaline the newer one. The practical reason for adding a second stone is supply. Fine opal with strong play-of-colour is hard to find and hard to set safely, so a month with only opal leaves buyers with few options in a ring. Tourmaline solved that. It comes in almost every colour, it is mined in quantity in Brazil, Mozambique, Madagascar and Pakistan, and it is hard enough to wear daily. So an October buyer picks between a soft stone with a rainbow effect nothing else can copy, and a hard stone in whatever colour they want. Both are correct answers. We stock both, and the right one depends entirely on what you are setting it into and who will wear it.
Which is better for an engagement ring, opal or tourmaline?
Tourmaline, in almost every case. GIA rates tourmaline 7 to 7.5 on the Mohs hardness scale and calls it generally suitable for everyday wear. Opal ranges from 5 to 6.5 and GIA places its toughness at the bottom of the scale it uses. An engagement ring gets worn daily for decades and takes hundreds of knocks against door handles, steering wheels and kitchen counters. Opal shows that history. We have re-polished opal engagement rings that were two years old and already scuffed across the dome. If a customer wants opal anyway, and some do because nothing else looks like it, we build it in a bezel with a raised edge and tell them to expect a re-polish every few years. That is a fair trade if they know it going in.
What causes the rainbow flashes in an opal?
Structure, not colouring agents. GIA explains that precious opal is made of sub-microscopic spheres stacked in a grid-like pattern, like layers of Ping-Pong balls in a box. Light waves travelling between those spheres bend, or diffract, and break apart into the colours of the rainbow. That effect is called play-of-colour. Sphere size decides which colours you see, which is why red play-of-colour is rarer and costs more than blue. It also explains why the flashes move when you tilt the stone: you are changing the angle light enters the grid. GIA divides opal into two classes on this basis. Precious opal shows play-of-colour. Common opal does not, and should be priced accordingly. If a seller cannot show you the flashes moving under a moving light, you are looking at common opal.
What is an opal doublet or triplet, and how do I spot one?
They are assembled stones built from a thin slice of real opal. GIA defines a doublet as a thin layer of opal cemented to a backing of obsidian, dyed black chalcedony, black glass, common opal or plastic. A triplet adds a domed top of colourless quartz or clear glass over that sandwich. Both exist so cutters can make a usable gem from opal too thin to stand alone, and both sell for a fraction of what solid opal costs. To spot one, look at the stone from the side. A doublet or triplet shows a flat, straight join line where the layers meet. A solid opal shows colour running through the edge. Ask the seller and get the answer written on the receipt. An assembled opal is honest goods sold honestly, and a problem only when sold as solid.
Why must an opal triplet never be soaked?
Because the glue fails before the stone does. GIA warns that prolonged exposure to water may weaken the adhesive in opal doublets and triplets. When that adhesive lets go, water seeps between the layers and the stone turns cloudy or grey from underneath. The play-of-colour disappears behind a milky film. The layers have to be separated and re-cemented by a cutter, which costs more than most assembled opals are worth. So a triplet ring comes off before washing dishes, before swimming and before a bath. Wipe it with a damp cloth and dry it right away. This is the most common way we see an opal ruined, and it is preventable. A solid opal tolerates a quick wash in warm soapy water, so knowing which one you own matters.
Can I put my opal or tourmaline in an ultrasonic cleaner?
No, for both stones. GIA says the use of ultrasonic and steam cleaners is not recommended for tourmaline, and for opal it says the safest cleaning method is warm soapy water, with other methods risking damage to the opal or the filler material. GIA's opal care page puts it plainly: the only safe way to clean opal is with warm, soapy water. The reason differs by stone. Ultrasonic vibration finds existing fractures in opal and opens them. Steam heat causes the sudden temperature change GIA warns fractures opal. With tourmaline the risk is heat altering the colour and thermal shock cracking stones that hold liquid inclusions. Warm water, mild dish soap, a soft toothbrush, rinse and pat dry. That works for both, and our bench cleans both by hand.
What is watermelon tourmaline and is it worth more?
Watermelon tourmaline is pink in the centre with green around the outside, and GIA notes these crystals are typically cut in slices to display that arrangement. The zoning happens because trace elements in the crystal changed in concentration or composition while it grew, so one crystal records its own growth history in bands. Price depends on how clean the colour separation is, how saturated both colours are and how symmetrical the slice sits. A sharp bullseye with a bright pink core and even green rim costs more than a muddy one. The catch is that slices are thin and wide, which makes them fragile in a ring. A watermelon slice belongs in a pendant or a bezel-set earring where nothing hits it edge-on.
Is Paraiba tourmaline expensive, and why?
Yes, and the copper content is the reason. GIA describes Paraiba as an intense violetish blue, greenish blue or blue tourmaline from the state of Paraiba, Brazil, with copper contributing that highly prized colour. GIA notes that a fine Paraiba's per-carat price is likely to rival the price of fine sapphire. Copper-bearing tourmaline has since been found in Nigeria and Mozambique, and those stones are sold under the Paraiba name too, which the trade argues about. Origin changes price, so a lab report matters at this level. Our honest view: most October birthdays do not need a Paraiba. A well-cut indicolite or a saturated rubellite gives a striking blue or pink at a fraction of the cost, and in a pendant nobody is checking the lab report.
Sources
- GIA: October Birthstones, Opal and Tourmaline Birthstone Information
- GIA: Opal Care and Cleaning Guide
- GIA Gem Encyclopedia: Opal Description
- GIA Gem Encyclopedia: Opal Quality Factors
- GIA Gem Encyclopedia: Tourmaline Description
- GIA: Tourmaline Care and Cleaning Guide
- GIA Gem Encyclopedia: Tourmaline Quality Factors
- GIA: Birthstones by Month
Data sourced September 2026. Hardness, toughness and cleaning guidance come from the GIA pages linked above. Setting and wear observations come from repair work on our own bench.
Visit Vanhess
We are a family-run studio at 2929 Barnet Highway in Coquitlam, and we designed and made most of what sits in our cases. Bring in an opal you own and we will check the edge under a loupe and tell you whether it is solid or assembled, free, while you wait. If you cannot decide between the two stones, come and hold both under the lights. Call us at +1 (604) 653-6449.
