September Birthstone

September's birthstone is sapphire, a variety of corundum prized for its deep blue color, Mohs 9 hardness, and centuries of royal symbolism.

Sapphire

September Birthstone

Corundum — Al₂O₃

Sapphire is a gem-quality variety of corundum — aluminum oxide — best known for its rich blue color, though it naturally occurs in nearly every hue. At Mohs 9, it is the second hardest mineral on Earth after diamond, making it exceptionally durable for all jewelry types including daily-wear rings. The finest blue sapphires come from Kashmir, Myanmar (Burma), and Sri Lanka; the United States (Montana) and Australia also produce notable material. Sapphire has been treasured by royalty, clergy, and collectors for over two millennia, associated with wisdom, loyalty, and nobility across most of the world's major cultures.

Hardness 9 / 10 Mohs
Mineral Corundum
Primary Color Blue (all shades)
Birthstone Since 1912 (modern)

Sapphire — Key Facts

Mineral Family
Corundum (Al₂O₃)
Sapphire belongs to the corundum mineral group. Pure corundum is colorless; trace elements introduce color. Iron and titanium produce blue; chromium produces pink to red (ruby); iron alone can produce yellow or green; vanadium produces violet. All corundum that is not red is classified as sapphire, regardless of color.
Color Range
Blue, pink, yellow, orange, green, colorless
Blue is the most prized color for sapphire, with "cornflower blue" (medium-intense, slightly violet blue) and "royal blue" (deep, rich blue) commanding premium prices. Fancy sapphires include pink (chromium), yellow (iron), orange, green, violet, and colorless (white) varieties. Padparadscha — a rare pinkish-orange color named after the lotus blossom — is the most valuable fancy sapphire.
Mohs Hardness
9 / 10
Sapphire's Mohs 9 hardness makes it the second hardest natural mineral after diamond (Mohs 10). It can only be scratched by diamond or another corundum stone (ruby or sapphire). This durability makes sapphire ideal for all jewelry types, including daily-wear rings exposed to regular abrasion. It also makes sapphire an industrial material — used in watch crystals, scientific instruments, and as a substrate in LED manufacturing.
Heat Treatment
Over 90% of sapphires are heat-treated
The vast majority of commercial sapphires are heat-treated at temperatures of 1,600–1,800°C to improve color and clarity. Heat treatment dissolves rutile silk inclusions, clears cloudy zones, deepens pale blues, and improves overall transparency. The treatment is permanent, stable, and universally accepted in the gem trade. Untreated (no-heat) sapphires command significant premiums, particularly in the fine and investment-grade market.
Primary Sources
Kashmir, Myanmar, Sri Lanka, Montana
Kashmir (India) produced the world's most coveted sapphires between 1881 and approximately 1900 — velvety, "sleepy" blue stones from high-altitude mines now largely exhausted. Myanmar's Mogok Valley yields intensely colored blue and pink sapphires. Sri Lanka (Ceylon) produces a wide range of colors, including fine cornflower blues and the famous orange-pink padparadscha. Montana (USA) produces unique blue-green and parti-colored sapphires. Australia and Madagascar are significant commercial sources.
Star Sapphire (Asterism)
Six-rayed star from rutile silk
Some sapphires contain dense, parallel needle-like inclusions of rutile (TiO₂) oriented in three sets at 60-degree angles. When cut as a cabochon, these inclusions reflect a six-rayed star across the dome of the stone — a phenomenon called asterism. Twelve-rayed stars occasionally occur when two sets of inclusions intersect at different orientations. The most famous star sapphire is the 563-carat Star of India at the American Museum of Natural History in New York.

Mohs Hardness Comparison

How sapphire ranks against other popular gemstones on the Mohs scale.

Diamond
10
Ruby / Sapphire (Corundum)
9
Alexandrite / Chrysoberyl
8.5
Spinel / Topaz
8
Aquamarine (Beryl)
7.75
Quartz / Amethyst / Citrine
7
Peridot / Sardonyx
6.75
Opal
6

The Mohs scale is ordinal — equal step differences do not represent equal absolute hardness differences. Diamond is roughly 4× harder than corundum in absolute terms. Sapphire is shown at 9 alongside ruby, as both are corundum.

Famous Sapphires

Star of India (563 ct)
One of the world's largest star sapphires at 563 carats, the Star of India is a grayish-blue cabochon on display at the American Museum of Natural History in New York. Mined in Sri Lanka approximately 300 years ago, it was donated to the museum by financier J. P. Morgan in 1900. The stone displays a clear, well-centered six-rayed star on both its top and bottom faces — unusual for a star sapphire. In 1964 it was famously stolen in a daring midnight heist and recovered 48 hours later.
Logan Sapphire (422.99 ct)
The Logan Sapphire is one of the largest faceted blue sapphires in the world at 422.99 carats. Set in a brooch surrounded by 20 round brilliant diamonds, it was donated to the Smithsonian Institution in 1960 by Mrs. John A. Logan. Of Sri Lankan origin, it displays a rich, pure blue color and exceptional clarity uncommon at such large size. It is displayed in the Janet Annenberg Hooker Hall of Geology, Gems, and Minerals in Washington, D.C.
Stuart Sapphire (104 ct)
The Stuart Sapphire is an oval blue sapphire weighing approximately 104 carats, set in the back of the British Imperial State Crown. Its history can be traced with reasonable confidence to the Stuart dynasty of the 17th century. The stone passed through the hands of James II of England when he fled to France in 1688, was acquired by the Hanoverian monarchs, and was eventually incorporated into the modern Imperial State Crown alongside the Black Prince's Ruby (actually spinel) and the Cullinan II diamond.
Princess Diana's Engagement Ring
Perhaps the most famous sapphire in modern times, the 12-carat oval Ceylon (Sri Lanka) sapphire surrounded by 14 solitaire diamonds was selected by Prince Charles for his 1981 engagement to Lady Diana Spencer. The ring was notable because it was chosen from a catalog rather than custom-made — an unusual choice for royal jewelry. After Diana's death, the ring passed to Prince William, who gave it to Catherine Middleton upon their engagement in 2010, where it continues to be one of the most photographed pieces of jewelry in the world.

History & Symbolism

Ancient Persia — The Sky Stone
Ancient Persians believed the sky was blue because it rested on a giant sapphire pedestal that reflected its color across the heavens. Sapphire was among the most prized stones in the Persian empire, worn by rulers as symbols of divine authority and cosmic order. The Persian word "safir" is one of the linguistic roots of the English word "sapphire," though the etymology is debated — ancient texts used gem names inconsistently and the stone referred to as "sappheiros" in ancient Greek is believed by many scholars to have been lapis lazuli, not corundum.
Ancient and Medieval Christianity
Sapphire held deep significance in medieval Christianity. The stones of the High Priest's breastplate described in Exodus include "sapphire" (though scholars debate whether this was actually lapis lazuli). By the medieval period, sapphire had become firmly associated with Christian clergy: bishops wore sapphire rings as symbols of heavenly wisdom and chastity. Pope Innocent III decreed in the 13th century that cardinal rings should be sapphire. The stone was believed to protect against poison, cure eye diseases, and preserve chastity.
Ancient India and Sanskrit Tradition
In Sanskrit, sapphire is "Shanipriya" — beloved of Saturn. In the Vedic astrological tradition (Jyotish), blue sapphire (Neelam) is the gemstone associated with the planet Saturn and is considered one of the most powerful and potentially transformative of the nine planetary gemstones. Worn correctly, it is believed to bring rapid success, wealth, and protection to those whom Saturn favors; worn by those for whom Saturn is inauspicious, it can have swift negative effects. This makes sapphire one of the few gemstones in any tradition explicitly warned against wearing without astrological consultation.
The Kashmir Discovery (1881)
In 1881, a landslide in the Zanskar Range of the Kashmir region of India exposed a pocket of extraordinary sapphire crystals at approximately 5,000 meters altitude. The Kashmir sapphires — characterized by their uniquely velvety, cornflower blue color with a slight hazy quality called "sleepiness" caused by minute, evenly distributed rutile silk inclusions — were unlike any sapphires seen before. The mine was worked intensively under the Maharaja of Kashmir until approximately 1900, when the primary pocket was exhausted. No subsequent find in Kashmir has matched the original deposit's output in quality or quantity.
Royal Symbolism in Modern Times
Sapphire has remained consistently associated with royalty through the modern era. In 1981, the blue sapphire chosen for Diana, Princess of Wales's engagement ring — now worn by Catherine, Princess of Wales — brought sapphire to global attention as the defining royal gemstone of the late 20th and early 21st centuries. The British Crown Jewels contain multiple significant sapphires, including the Stuart Sapphire in the Imperial State Crown. Sapphire engagement rings have experienced a sustained surge in popularity since the 2010 engagement of Prince William and Catherine Middleton.

Care Tips for Sapphire Jewelry

Warm soap and water works well
Sapphire is chemically stable and resistant to most household chemicals. Clean with warm water, a drop of mild dish soap, and a soft toothbrush. Rinse thoroughly and dry with a lint-free cloth. This is safe for all sapphires, including those that have been heat-treated.
Ultrasonic cleaning: check treatment first
Most untreated and heat-treated sapphires tolerate ultrasonic cleaning. However, sapphires that have been fracture-filled, surface-coated, or treated with beryllium diffusion should never go in an ultrasonic cleaner, as vibrations can displace or damage the treatment. If you are unsure of your stone's treatment status, stick to manual cleaning.
Suitable for all jewelry types
At Mohs 9, sapphire is durable enough for daily-wear rings, bracelets, and any type of setting. It withstands the knocks and abrasions of everyday life better than most gems. Prong, bezel, and channel settings are all appropriate. No special protective setting is required for normal use.
Keep away from diamond in storage
Diamond (Mohs 10) can scratch sapphire, and sapphire can scratch virtually every other gem in your collection. Store sapphire jewelry in a separate compartment, soft pouch, or fabric-lined box to prevent contact scratches — both to protect your sapphire from diamond and to protect other softer gems from the sapphire.
Avoid prolonged strong sunlight for some fancy colors
Blue sapphires are generally very stable in color. However, some natural yellow and pink sapphires can experience slight color fading with prolonged, intense UV exposure over years. Store jewelry away from direct sunlight when not in use as a precaution, particularly for fancy-colored sapphires.
Professional check every 1-2 years
Have a jeweler inspect prongs and settings annually or every two years, especially for daily-wear rings. While sapphire itself is nearly indestructible, the metal setting can wear, loosen prongs, or develop micro-fatigue cracks over time. Catching a worn prong early prevents losing a stone.

Gift Ideas for September Birthdays

Blue Sapphire Solitaire Ring
A classic oval or round blue sapphire solitaire set in white gold or platinum is timeless and deeply meaningful for a September birthday. Look for a cornflower or royal blue stone from Sri Lanka for strong value; Kashmir origin commands the highest premium.
Sapphire and Diamond Halo Pendant
A round sapphire surrounded by a diamond halo on a fine gold chain is a versatile, elegant gift suitable for any age. Blue sapphire's color pops beautifully against white gold and the diamond surround maximizes brilliance.
Star Sapphire Cabochon Ring
A star sapphire cut as a smooth cabochon showing a crisp, well-centered six-rayed star is a genuinely unique and conversation-starting gift. Blue-gray or blue star sapphires from Sri Lanka or India offer good quality at a range of price points.
Padparadscha Sapphire Earrings
Padparadscha sapphire — the rare pinkish-orange variety — is the most exotic and prized fancy sapphire. Small pear or oval padparadscha stones set in rose gold earrings make an extraordinary and distinctive gift for a gemstone enthusiast.
Montana Sapphire Ring
American-mined Montana sapphires in teal, blue-green, and parti-color (green-yellow-blue in a single stone) are a distinctive, ethically sourced alternative to Asian sapphires. Their unique color range appeals to buyers who want something different from the classic blue.
Sapphire Birthstone Stacking Set
A set of two or three thin stacking rings featuring small sapphire accents in different cuts (round, marquise, pear) gives the wearer a flexible, modern look and makes a stylish September birthday gift for any age.

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Summary

September's birthstone is sapphire, a variety of corundum prized for its deep blue color, Mohs 9 hardness, and centuries of royal symbolism.

How it works

  1. September's birthstone is sapphire, recognized on the modern list since 1912.
  2. Scroll through the hero card to see sapphire's key mineral facts at a glance.
  3. Browse the Key Facts grid for hardness, color, origin, and historical context.
  4. Read the Famous Sapphires section to learn about the most celebrated stones in the world.
  5. Explore the History and Symbolism section to understand sapphire's cultural legacy across civilizations.
  6. Check the Care Tips section to keep sapphire jewelry in top condition.
  7. Use the Gift Ideas section to find the right present for a September birthday.
  8. Use the month selector at the bottom to look up birthstones for any other month.

Use cases

  • Find a meaningful birthstone gift for a September birthday.
  • Learn what makes sapphire the ideal everyday-wear gemstone.
  • Understand why sapphires come in colors other than blue.
  • Discover the famous sapphires worn by royalty throughout history.
  • Care for sapphire jewelry to preserve its brilliance for decades.
  • Choose between Kashmir, Myanmar, and Sri Lanka sapphires by quality.
  • Explore affordable sapphire alternatives for any budget.
  • Look up birthstones for any month using the interactive month selector.

Frequently Asked Questions

Last updated: 2026-06-10 · Reviewed by Nham Vu