Three shades of the same quiet blue - spinel rings in 18K gold, made between 1920 and 1950, resting on silk. The baby blue spinel rings.
Spinel is the stone history kept mistaking for something else. For centuries it was taken for ruby and set in crowns under the wrong name, and while the mineralogists eventually sorted out the paperwork, the stone itself never needed correcting - it simply went on being beautiful under its own flag. It runs through the pieces that pass across my desk in reds, blues and greens, and it deserves to be known by name.
What spinel actually is
Spinel is its own mineral - magnesium aluminium oxide - not a variety of anything else. It grows in the same marble that produces ruby and sapphire, which is exactly why the confusion started: the crystals come out of the same ground, in nearly the same reds. At 8 on the Mohs scale it sits just below corundum, more than hard enough for daily wear, and it takes a beautiful polish. Unlike ruby and sapphire it is singly refractive, so its colour reads pure and even rather than shifting as the stone turns - one of the small optical signatures a gemologist uses to tell them apart in seconds.
Natural spinel comes in red and pink where chromium does the colouring, in flame orange, in violet and steely grey, and - rarest of all - in a vivid blue coloured by cobalt. The historical sources were Badakhshan on the borders of Afghanistan and Tajikistan, whose rose-red stones were traded for centuries as "balas rubies", and later Burma and Sri Lanka.
The stone in the crown
The most famous ruby in the world is not a ruby. The Black Prince's Ruby, the great red stone at the front of the British Imperial State Crown, is a spinel - and so is the Timur Ruby beside it in the royal collection. Nobody was swindled; before modern mineralogy there was simply no way to separate the two red stones, and for centuries no reason to try. When chemistry finally split them in the nineteenth century, spinel got the humiliating label of impostor, its price collapsed, and for a hundred years it became the connoisseur's quiet bargain. That chapter is closing fast: fine red and cobalt-blue spinels now sell for serious money, and the trade that once looked down on the stone spent 2016 adding it to the official birthstone list for August, beside peridot.
A bow of Swedish gold from 1946 holding one pale blue stone against a pink linen shirt - the big blue spinel pendant worn as it was meant to be.
The Scandinavian blue
In Sweden and Denmark, the mid-century decades gave spinel a golden age of its own. Goldsmiths of the 1930s to 1960s loved a calm, even, pale blue stone in warm 18K gold - icy against the metal, quiet enough for every day, and cool in exactly the way that suited the era's clean lines. Rings, bow pendants and ribbon brooches carried that blue across three decades, usually with the year stamped right into the shank, and the combination has aged wonderfully: the pieces read as fresh today as the day they left the bench.
White spinel had its moment in the same workshops - bright, clear stones in hearts, bows and studs - and green spinel turned up in cocktail rings with a colour no other stone of the period quite matched. If you collect Scandinavian vintage gold, spinel is simply part of its vocabulary.
Icy drops in brushed 18K gold - vintage spinel earrings doing winter light all year round.
Spinel or something else?
| Looks like | How spinel differs |
|---|---|
| Ruby | Spinel is singly refractive with one pure red; ruby shows two slightly different reds as it turns and fluoresces differently. A refractometer settles it instantly |
| Sapphire | Cobalt-blue spinel is rarer than blue sapphire and often more electric in tone; a refractometer separates the two minerals in moments |
| Aquamarine | Aquamarine shows a soft blue-green two-tone colour as it turns; spinel holds one pure, even blue with a steelier calm |
| Garnet | Red garnet leans brick and brown; red spinel holds a cooler, sweeter red and is noticeably harder |
Buying spinel well
Buy colour first: a vivid red or a true cobalt blue is the prize, and grey - the fashion world's recent darling - offers real beauty at gentler prices. With vintage Scandinavian pieces, buy the whole object: the year in the hallmark, the gold, the design and that unmistakable calm blue belong together, and together they are the point. And as with every stone in this book, buy from sellers who describe what they sell precisely and answer direct questions directly.
Frequently asked questions
Is spinel a real gemstone?
Entirely. It is its own natural mineral with its own name, not an imitation of anything - the confusion with ruby is historical, not chemical.
Is the Black Prince's Ruby really a spinel?
Yes. The great red stone in the British Imperial State Crown is a polished red spinel, and the Timur Ruby in the same collection is another. Both were named centuries before mineralogy could tell the stones apart.
Why is pale blue spinel so common in Swedish vintage gold?
Because the era loved it. From the 1930s to the 1960s that calm, even blue was a signature of Scandinavian goldsmithing - cool stone, warm 18K gold, clean lines - and it was made in quantity. It is one of the most recognisable looks in Swedish vintage jewelry.
Is spinel a birthstone?
Yes, and a new one: in 2016 spinel was added as a birthstone for August, sharing the month with peridot.
How hard is spinel?
8 on the Mohs scale - below ruby and sapphire, above almost everything else. An antique spinel ring handles daily wear with ordinary care.
How can I tell spinel from ruby?
Not by eye across a market stall. Spinel is singly refractive and ruby doubly, which a gemologist reads in moments with basic instruments - so for a stone sold as either at a serious price, ask for testing.
Read next: Garnet vs ruby · Rubies in antique jewelry · Are sapphires only blue?
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