The September birthstone is sapphire, a variety of corundum best known in blue but found in almost every color except red. Sapphire measures 9 on the Mohs scale and marks the 5th and 45th wedding anniversaries.
A pink, yellow, or green stone can still be a September birthstone because the name sapphire “can also apply to any corundum that’s not red and doesn’t qualify as ruby,” according to the Gemological Institute of America (GIA).
Only red corundum is ruby, the July birthstone. The best-known September birthstone is the 12-carat blue sapphire in the engagement ring first worn by Princess Diana, later given to the Princess of Wales. In the UK, lapis lazuli is an official alternative September birthstone.
Table of Contents
What is the September birthstone?
Sapphire is the official September birthstone on the GIA list; the British list adds lapis lazuli as an alternative. The table summarizes sapphire’s key properties.
| Property | Sapphire (September birthstone) |
|---|---|
| Mineral | Corundum (every color except red) |
| Mohs hardness | 9 |
| Toughness | Excellent; no cleavage |
| Colors | Blue; also violet, purple, pink, orange, yellow, green and multicolor (“fancy” sapphires) |
| Historic sources | Kashmir, Myanmar, Sri Lanka |
| Other sources | Madagascar, Australia, Thailand, Cambodia, United States (Montana) |
| Wedding anniversaries | 5th and 45th |
| Zodiac signs for September birthdays | Virgo (to about September 22) and Libra (from about September 23) |
Is there more than one September birthstone?
On the U.S. list, sapphire is September’s only birthstone; the UK list also includes lapis lazuli, an opaque, deep blue rock flecked with gold-colored pyrite. The U.S. and UK lists are compared in the Birthstones by Month chart.
September birthstone colors
Sapphire is best known in deep blue, but “fancy” sapphires occur in violet, green, yellow, orange, pink, purple and intermediate hues, and some show more than one color. GIA’s sapphire description identifies several special types.
| Type | Appearance | Notes |
|---|---|---|
| Blue sapphire | Deep, intense blue is most valued | Kashmir stones are prized for a “velvety” quality |
| Fancy sapphire | Pink, yellow, orange, green, purple, violet | Any non-red corundum |
| Padparadscha | Pinkish orange | Rare; named after the lotus flower |
| Color-change sapphire | Blue in daylight, purple in incandescent light | Shifts with the light source |
| Star sapphire | A six-rayed star on a cabochon-cut stone | Caused by light reflecting from needle-like inclusions (asterism) |
Sapphire vs. ruby: where the September birthstone begins
Sapphire and ruby are the same mineral, corundum; red corundum is ruby and every other color is sapphire.
Pink sapphire and pale ruby sit close together, and laboratories and markets can draw the line differently. The July Birthstone guide covers ruby.
Blue sapphire compared with other blue September birthstone look-alikes
| Feature | Blue sapphire (September) | Tanzanite (December) | Aquamarine (March) |
|---|---|---|---|
| Mineral | Corundum | Zoisite | Beryl |
| Mohs hardness | 9 | 6–7 | 7.5–8 |
| Typical blue | Medium to deep blue | Blue-violet | Pale to medium greenish blue |
| Birthstone guide | This page | December Birthstone | March Birthstone |
Sapphire treatments: what September birthstone buyers should ask
“Heat treatment is common – and the results permanent,” according to GIA, but some sapphires are lattice-diffusion treated, fracture-filled with glass or dyed, and these need gentler care. Ask for the treatment status before buying.
| Treatment | Durability | Cleaning |
|---|---|---|
| Untreated | Very durable | Warm soapy water; ultrasonic and steam usually safe |
| Heat-treated | Very durable; results permanent | Warm soapy water; ultrasonic and steam usually safe |
| Lattice diffusion | Color can be removed if the stone’s surface is damaged and the treatment is shallow | Avoid repolishing and recutting |
| Glass-filled (high-lead glass) | Filler can be damaged by chemicals, including mild acids such as lemon juice | Damp cloth only |
| Dyed | Color can be affected by cleaning | Damp cloth only |
September birthstone meaning and history
Sapphire has been associated with royalty, faith and truth for centuries; medieval clergy wore sapphires because they “symbolized Heaven.” GIA highlights these famous stones and associations:
| Stone or tradition | Detail |
|---|---|
| Royal engagement ring | A 12-carat blue sapphire surrounded by diamonds, first worn by Princess Diana |
| Rockefeller Sapphire | 62.02 carats |
| Medieval Europe | Worn by clergy as a symbol of Heaven |
| Historic sources | Kashmir, Myanmar and Sri Lanka |
These associations are cultural; they describe tradition, not gemological properties.
Caring for a September birthstone
Sapphire’s hardness of 9 and excellent toughness, with no cleavage, make it one of the best gems for everyday rings. Follow GIA’s care guidance:
- Clean any sapphire with warm, soapy water. GIA says this “is always safe.”
- Use ultrasonic and steam cleaners only on untreated or heat-treated sapphires.
- Clean fracture-filled or dyed sapphires with a damp cloth only.
- Keep sapphires away from boric acid powder, which “will etch the surface of even untreated stones,” and keep treated stones away from mild acids such as lemon juice.
What the September birthstone is not
The September birthstone is often misunderstood. The points below separate the facts.
- It is not only blue. Pink, yellow, green and other non-red corundum are all sapphire.
- It is not a different mineral from ruby. Both are corundum.
- It is not tanzanite. Tanzanite is a softer, blue-violet zoisite and a December birthstone.
- It is not the only September stone in the UK. Lapis lazuli is a British alternative.
Frequently asked questions
What color is the September birthstone?
The September birthstone, sapphire, is usually deep blue, but pink, yellow, orange, green, purple and color-change sapphires are also September birthstones.
Is sapphire good for an engagement ring?
Yes. Sapphire measures 9 on the Mohs scale with excellent toughness and no cleavage, which makes it one of the most durable gems for daily-wear rings.
What anniversary is sapphire for?
Sapphire is the gemstone for the 5th and 45th wedding anniversaries, according to GIA.
