What it is confused with
Blue glass, tanzanite, iolite, blue spinel and synthetic sapphire. Treatments such as beryllium diffusion need a laboratory to detect.
Blue, also pink, yellow, green, colorless
Sapphire birthstone
Sapphire, the birthstone for September, is aluminum oxide (Al₂O₃) — corundum colored by iron and titanium, blue, also pink, yellow, green, colorless, rated 9 on the Mohs scale. Traditionally, it is associated with judgment, focus and keeping a promise — attributed, not demonstrated.
- Mohs hardness
- 9 scratches window glass
- Crystal system
- Trigonal Al₂O₃
- Pliny, AD 77
- Book 37.39 as “sapphiros”
- Main sources today
- Sri Lanka also Madagascar, Myanmar
Pliny, Natural History, tr. Bostock and Riley.
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Properties
Composition
Aluminum oxide (Al₂O₃) — corundum colored by iron and titanium
Hardness (Mohs)
9
Crystal system
Trigonal
Color
Blue, also pink, yellow, green, colorless
Mined in
Sri Lanka, Madagascar, Myanmar, Australia, USA (Montana)
Worth knowing
Padparadscha — a pink-orange sapphire named after the lotus flower — is the rarest color and outprices most blues.
History
Worn by medieval clergy as a symbol of heaven; prized in Persia and Kashmir.
Buying
Buying Sapphire: fakes, value and treatments
What decides the price
Velvety, saturated blue is valued most, with Kashmir, Burma and Sri Lanka the famous sources. Heating is routine; sapphire comes in every color except red, which is ruby.
Where it is used
Synthetic sapphire covers luxury watch faces and some smartphone camera lenses because it is so scratch-resistant.
A less familiar fact
The engagement ring given to Diana, Princess of Wales, and later to Catherine, is set with a 12-carat Sri Lankan sapphire.
Practical
Caring for Sapphire
How to clean it
Warm soapy water. Safe in ultrasonic unless fracture-filled.
How to tell it is real
Heat treatment is near-universal and disclosed. Untreated sapphire commands a large premium and should come with a lab report — no report, assume treated.
How hard is Sapphire?
Sapphire is corundum, like ruby, and second only to diamond here. It is tough as well as hard, which is why synthetic sapphire is used for watch crystals and natural sapphire is a common alternative to diamond in engagement rings. Only Ruby shares its place on our scale. Among the stones in this reference, the next softer is Alexandrite (8.5) and the next harder Diamond (10).
Sapphire, at 9, is harder than 40 of the other 42 stones here and softer than 1.
Primary source
What Pliny the Elder wrote about Sapphire
“For sapphiros, too, is refulgent with spots like gold. It is also of an azure colour, though sometimes, but rarely, it is purple; the best kind being that which comes from Media.”
Pliny the Elder, The Natural History, translated by John Bostock and H. T. Riley (London: H. G. Bohn, 1855–57), book 37, chapter 39 — read the original text.
Pliny’s sapphiros was not our sapphire: an opaque blue stone flecked with gold is lapis lazuli. The name passed to transparent blue corundum later. Who Pliny was and why we quote him →
Traditional associations
Sapphire is traditionally associated with judgment, focus and keeping a promise. Chakra in crystal practice: Throat, Third Eye. Element: Air.
Questions about Sapphire
What is Sapphire made of?
Aluminum oxide (Al₂O₃) — corundum colored by iron and titanium, crystallizing in the trigonal system.
Which month is Sapphire the birthstone for?
September. It is also an alternative stone for April.
Where does Sapphire come from?
Sri Lanka, Madagascar, Myanmar, Australia, USA (Montana).
Can Sapphire be worn every day?
Yes. It rates 9 on the Mohs scale, and the main thing to watch is fracture filling in some stones.
Sources
Statements of fact on this page were checked against these sources in October 2026. How we choose and check sources: editorial policy.
Cite this page
AstroHot. “Sapphire Birthstone: The September Stone and Its Meaning.” Accessed October 28, 2026. https://astrohot.com/crystals/gemstones/sapphire/
For Wikipedia
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