September Birthstone
September gets the aristocrat of the chart: sapphire, the royal blue gem of crowns, engagement rings and five-thousand-year-old star lore. It is the second-hardest gem in common use — only diamond beats it — which means a September stone can be worn daily for a lifetime and passed down still looking new.
Sapphire also hides a family secret much like garnet's: it isn't only blue. Sapphire is the mineral corundum, and every color it grows in except red counts as sapphire — pinks, yellows, greens, violets and the celebrated pink-orange padparadscha. (The red one has its own name: ruby.) Here's the full picture — the stone, the color, the history, and what drives sapphire prices from modest to legendary.
The September birthstone
What color is the September birthstone?
The September birthstone color is blue — specifically the rich, royal 'sapphire blue' that sits between cornflower and midnight, the shade every chart and birthstone-jewelry line uses for the month. The most prized stones hold a vivid medium blue that stays alive in any light rather than going ink-dark.
Fancy sapphires widen September far beyond blue: pink, yellow, violet, green, white, and the pink-orange padparadscha — among the most expensive colored stones in the world. Any of them is a genuine September sapphire; only the chart swatch is blue.
How September got its birthstone
Sapphire's history is a history of authority: Persian cosmology imagined the sky as the reflection of a giant sapphire; medieval clergy wore it as the stone of heaven; and royalty adopted it as proof of wisdom and divine favor — a tradition running unbroken into the modern era, where a 12-carat Ceylon sapphire engagement ring passed from Princess Diana to Catherine, Princess of Wales, and single-handedly revived the sapphire engagement ring. Lore also made it a truth-teller: a sapphire was said to refuse to shine for the dishonest.
It has held September on every list, traditional and modern, without challenge. The mineralogy caught up later: 'sapphire' and 'ruby' were only understood as the same mineral — corundum — in the late 18th century, which is why the red stone kept its own ancient name while every other color of corundum became a sapphire.
Choosing & caring for September birthstones
Color rules price: a vivid, evenly saturated medium blue beats both pale stones and over-dark ones, and origin adds mystique — Kashmir, Burma and untreated Ceylon stones carry auction premiums. Assume heat treatment unless a lab report says otherwise; 'no indications of heating' from a serious lab can multiply the price, so never pay an unheated premium without papers. Watch for lab-created sapphire (chemically identical, honestly sold for a fraction — fine if labeled, fraud if not) and for 'composite' or lead-glass-filled stones at too-good prices. Hardness 9 makes sapphire the best colored stone there is for an everyday ring.
Frequently asked questions
What is the September birthstone?
Sapphire — on both the traditional and modern lists, unchallenged for centuries. Blue is the signature, but every color of the mineral corundum except red counts as sapphire.
What color is the September birthstone?
Royal blue — the classic 'sapphire blue' between cornflower and midnight. Fancy sapphires in pink, yellow, violet, green and padparadscha orange are equally genuine September stones; the chart simply shows blue.
Are sapphire and ruby the same mineral?
Yes — both are corundum. Chromium makes it red, and red corundum is called ruby; iron and titanium make it blue, and blue (or any other non-red color) is sapphire. The two names predate the mineralogy by millennia, so the red stone kept its own identity.
Why are sapphires so durable?
Corundum is 9 on the Mohs scale — only diamond among common gems is harder. In practice nothing you encounter day to day will scratch it, which is why sapphire is the classic recommendation for engagement rings and daily-wear jewelry, and why it's also used industrially for watch glass and scratchproof windows.
Is a heated sapphire fake?
No — gentle heating to improve color and clarity has been standard for centuries, is stable forever, and is accepted throughout the trade; the majority of sapphires sold are heated. What matters is disclosure and price: unheated stones deserve their premium only with a lab report, and undisclosed lead-glass-filled composites are the actual trap to avoid.
See the full birthstones-by-month chart or jump to April, August, December, February, January, July, June, March, May, November, October.
Last updated 2026-07-19