September Birthstone: Sapphire
September's birthstone is sapphire. Here's what the stone means, why it holds up so well to daily wear, the colours it actually comes in, and how to pick a good one as a gift.
Key Takeaways
- The modern birthstone for September is sapphire, the gem-quality form of the mineral corundum.
- Sapphire ranks 9 on the Mohs hardness scale with excellent toughness and no cleavage, so it stands up to daily wear better than almost any stone except diamond.
- It is famous for blue, but sapphire also comes in pink, yellow, green, orange, purple, and colourless. Anything other than blue is called a "fancy" sapphire.
- Sapphire and ruby are the same mineral. Red corundum is ruby; every other colour is sapphire.
- Because it's so hard-wearing, sapphire is one of the safest coloured-stone choices for an engagement ring or an everyday piece.
What is the September birthstone?
September's birthstone is sapphire. It has been the month's stone in the modern Western birthstone list for a long time, and unlike a few months that carry several options, September is straightforward: blue sapphire is the one most people picture, and there's no rival traditional stone competing for the spot.
Sapphire is the gem variety of a mineral called corundum, which is crystallised aluminium oxide. Here's the fact that surprises most people at our counter: ruby is also corundum. Red corundum gets the name ruby; corundum in any other colour is called sapphire. So a sapphire and a ruby are chemically the same stone, separated only by colour and a naming tradition. For the wider family of coloured stones, our Full Gemstone Guide walks through how species and varieties relate.
Meaning and history
Sapphire has carried associations with sincerity, truth, faithfulness, and nobility for centuries, which is part of why it shows up so often in engagement and anniversary jewellery. According to the Gemological Institute of America (GIA), the elite of ancient Greece and Rome believed blue sapphires protected the wearer from harm and envy, and medieval Europeans thought the stone could cure eye disease and plague boils.
It has a long run as a royal and clerical stone too, set into crowns and worn by the clergy across Europe. The most famous modern example is the blue sapphire engagement ring first worn by the late Princess Diana and now by the Princess of Wales, which did more for sapphire's popularity than any marketing campaign ever could.
Durability: why sapphire is a workhorse
This is the part I push hardest when someone asks about a coloured stone they'll wear every day. Sapphire is genuinely tough. GIA rates corundum at 9 on the Mohs scale, second only to diamond at 10, with excellent toughness and no cleavage (cleavage is a built-in plane of weakness that makes some stones split when knocked). On our Coquitlam bench we set sapphires into everyday rings without the worry we'd have over a softer stone like opal or emerald.
For comparison, here's how sapphire stacks up against a few stones people often weigh against it:
| Stone | Mohs hardness | Everyday-wear verdict |
|---|---|---|
| Diamond | 10 | Hardest; ideal |
| Sapphire / Ruby (corundum) | 9 | Excellent for daily wear |
| Aquamarine (beryl) | 7.5–8 | Good, treat with some care |
| Amethyst (quartz) | 7 | Fine for occasional wear |
| Emerald (beryl) | 7.5–8 but brittle | Fragile; handle gently |
Hardness values above follow the standard Mohs scale used by GIA. The takeaway: sapphire is one of the few coloured stones I'm comfortable recommending for a ring that never comes off.
Colour range
Most buyers want blue, and blue sapphire is the classic. But the colour story is bigger than that. Per GIA, blue sapphire ranges from a greenish-blue through to a violet-blue, and the most prized is a vivid, pure blue that isn't too dark or too washed out.
Beyond blue, sapphire shows up in pink, yellow, orange, green, purple, and colourless. Anything that isn't blue (and isn't red, which would make it a ruby) gets the label "fancy sapphire." There's also padparadscha, a rare and pricey pinkish-orange sapphire whose name comes from the Sinhalese word for a lotus blossom. If you want a coloured stone that isn't the expected blue, sapphire gives you more honest options than almost any other gem, and they're all just as hard-wearing.
A note on treatments
Most sapphires on the market are heat-treated to improve colour and clarity, and that's a stable, widely accepted practice. Untreated stones with strong natural colour command a premium. If a treatment matters to you, ask for it in writing on the receipt or on an independent lab report. We're happy to point you toward what's been treated and what hasn't.
Sapphire as a gift
Sapphire is the traditional gift for the 5th and 45th wedding anniversaries, on top of being the September birthday stone, so it covers a lot of gifting ground. A few practical ideas:
- Stud earrings or a simple pendant for a first sapphire gift. Low risk on sizing, easy to wear daily.
- A blue sapphire ring for a milestone birthday or anniversary. The hardness means it won't look tired in a year.
- A fancy-colour sapphire (yellow, pink, teal) for someone who already owns plenty of blue or wants something less expected.
- A sapphire engagement ring if the couple wants colour and durability without a diamond's price per carat.
If you're matching a gift to a different month, our parent guide Birthstones by Month: Modern & Traditional Stones lists every stone, and you can jump straight to neighbouring months like March Birthstone: Aquamarine, or earlier ones such as January Birthstone: Garnet and February Birthstone: Amethyst.
Frequently Asked Questions
What is the birthstone for September?
Sapphire is the modern birthstone for September. It's the gem variety of the mineral corundum and is best known in blue, though it occurs in many colours.
How hard is sapphire and is it good for an engagement ring?
Sapphire is a 9 on the Mohs scale with excellent toughness and no cleavage, according to GIA. That makes it one of the most durable coloured stones and a sound choice for an engagement ring or any piece worn every day.
What colours does sapphire come in?
Blue is the classic, ranging from greenish-blue to violet-blue. Sapphire also comes in pink, yellow, orange, green, purple, and colourless. Non-blue stones are called fancy sapphires, and the rare pinkish-orange variety is padparadscha.
Are sapphire and ruby the same stone?
They're the same mineral, corundum. Red corundum is called ruby; corundum in every other colour, including blue, is called sapphire.
Are most sapphires treated?
Yes. Most sapphires are heat-treated to improve colour and clarity, which is a stable and accepted practice. Untreated stones with strong natural colour cost more. Ask for treatment disclosure in writing or on a lab report.
What anniversary is sapphire for?
Sapphire is the traditional gift for the 5th and 45th wedding anniversaries, in addition to being September's birthstone.