September’s Stone: Ten Things Worth Knowing About Sapphire
Every September, sapphire gets its moment. And it deserves it, because this is one of the few stones that genuinely earns its reputation rather than trading on marketing. Kings wore it. Clergy wore it. It survives being knocked against a kitchen worktop for forty years and still looks like it did the day it was set.
Here are ten facts we think are worth knowing before you buy one, wear one, or inherit one.
1. It isn’t its own mineral. It’s corundum.
Sapphire and ruby are the same mineral: corundum, crystallised aluminium oxide. The only thing separating them is trace chemistry. Iron and titanium creeping into the crystal lattice give you blue. Chromium gives you red, and red corundum gets called ruby. Everything else in the corundum family, every other colour, is a sapphire.
So when someone asks whether sapphire is a “natural stone” or a “gemstone,” the answer is both. It’s a naturally occurring mineral that forms in metamorphic and igneous rock over millions of years, and it’s classed as a precious gemstone alongside diamond, ruby and emerald.
2. Blue is the default, not the rule.
Sapphire comes in every colour of the rainbow except red. Pink, yellow, green, violet, peach, grey, colourless. The trade calls anything non-blue a “fancy sapphire” and names the colour first: pink sapphire, yellow sapphire, and so on.
The rarest of the lot is padparadscha, a pinkish orange named after the lotus blossom. Genuine ones from Sri Lanka command prices that make people blink, and the definition of where pink ends and padparadscha begins is still argued over by labs.
3. It’s a 9 on Mohs, and toughness matters more than that number.
Sapphire sits at 9 on the Mohs scale of hardness, second only to diamond at 10. But the number people should actually care about is toughness, which measures resistance to chipping and breaking rather than scratching. Sapphire has excellent toughness and no cleavage plane, meaning there’s no direction along which it wants to split.
That combination is why sapphire is the sensible choice for an engagement ring on someone who works with their hands. Emerald is roughly the same hardness as quartz and full of fractures. Sapphire just gets on with it.
4. The Persians thought the sky was a reflection of it.
Ancient Persian belief held that the earth rested on a giant sapphire, and that the sky was blue because it reflected the stone. That’s the oldest bit of sapphire lore we know of, and it sets the tone for everything that follows.
Greeks and Romans wore blue sapphire as protection from harm and envy. Medieval European clergy wore it because blue represented Heaven. Ordinary people believed it cured plague boils, treated eye disease and worked as an antidote to poison. Across every one of those cultures the stone carried the same associations: sincerity, truth, faithfulness, nobility. Which is exactly why it keeps ending up in engagement rings.
5. Sri Lanka has been producing it for more than two thousand years.
If you want the true origin story, it starts in Sri Lanka. The island has been mining gem gravels around Ratnapura, which translates roughly as “city of gems,” since antiquity. Traders were moving Ceylon sapphires through Persian and Roman markets while most of Europe was still using flint.
Sri Lanka remains one of the two or three most important sources today. The stones tend toward a lighter, brighter blue than Burmese material, and the island produces an outsized share of the world’s star sapphires and padparadschas.
6. Kashmir sapphire is the holy grail, and it barely exists.
In 1881 a landslide in the Zanskar range of the Padar region of Kashmir exposed a sapphire deposit at roughly 4,500 metres. The material coming out of it was unlike anything the trade had seen: a deep cornflower blue with a soft, sleepy, velvety quality caused by microscopic inclusions scattering light through the stone.
The main deposit was essentially worked out within about seven years. Everything sold as Kashmir sapphire today came out of that short window or the scraps that followed. It’s the reason a certified Kashmir stone can fetch many times the price of an identical-looking sapphire from anywhere else, and it’s also the reason lab certification matters enormously at that end of the market.
7. Today’s stones come from a much wider map.
Current commercial production is spread across Madagascar, which has grown into a dominant source since the 1990s, Sri Lanka, Myanmar, Australia, Thailand, Cambodia, Nigeria, Tanzania and Montana in the United States. Montana sapphire in particular has built a real following among buyers who want a traceable, ethically documented stone with a domestic supply chain.
Ask where a stone came from. A good jeweller will know, and if they don’t, that tells you something too.
8. Almost every sapphire has inclusions, and some of them are the point.
Flawless sapphire is vanishingly rare. Most stones carry internal features, and the most characteristic is “silk,” which is a fine network of needle-like rutile crystals that grew inside the corundum along its crystal structure.
Silk is not a defect to be embarrassed about. It’s the velvety softness in Kashmir material. It’s also what creates a star sapphire: when silk is dense enough and oriented correctly, and the stone is cut as a cabochon rather than faceted, light reflects off those needles as a six-rayed star that moves across the dome as you tilt it.
As a rough guide, expect visible inclusions under 10x magnification in nearly every natural sapphire you look at. Eye-clean at arm’s length is a realistic standard. Loupe-clean is a rare and expensive one. A stone with absolutely no inclusions at all should raise your suspicions rather than your enthusiasm, because it may well be synthetic.
9. Heat treatment is normal, and disclosure is what counts.
The large majority of sapphire on the market has been heat treated, often at temperatures above 1,600°C, to improve colour and dissolve silk for better clarity. The result is stable and permanent, and heated stones can be cleaned in an ultrasonic or steam cleaner with no issue.
Other treatments carry more baggage. Lattice diffusion pushes colour-causing elements into the surface layer. Fracture filling with glass or resin props up stones that would otherwise fall apart. Dyeing does what it says. These need to be disclosed, they affect value substantially, and stones treated this way should only ever be cleaned with a damp cloth and mild soap.
For everyday care of an untreated or heat-treated sapphire, warm soapy water and a soft brush is all you need.
10. The famous ones tell you how the stone travels through history.
The Stuart Sapphire, roughly 104 carats, entered the Royal Collection through the House of Stuart and now sits in the back of the Imperial State Crown. The Logan Sapphire, 422.99 carats from Sri Lanka, is one of the largest faceted blue sapphires in the world and lives at the Smithsonian, donated by Rebecca Guggenheim Logan in 1971. The Star of India, 563.35 carats, sits at the American Museum of Natural History in New York after a spell as stolen property in 1964. John D. Rockefeller Jr. bought the 62.02 carat Rockefeller Sapphire in 1934 and had it recut and reset more than once.
And then the one everybody actually pictures: the 12 carat oval Ceylon sapphire surrounded by diamonds that Prince Charles gave Diana in 1981, chosen off the shelf from a Garrard catalogue rather than commissioned, which caused a small scandal at the time. It’s now on Catherine’s hand, and it single-handedly resurrected sapphire engagement rings for two generations of buyers.
Looking for a sapphire this month
We’ve got a range of sapphire pieces in the shop, from rings to necklaces to matching earring sets, including a few antique and second-hand finds. If you’re shopping for a September birthday, or thinking about sapphire for a ring, come and talk to us about treatment and certification before you commit to anything.