For centuries, spinel lived in the shadow of better-known stones. Some of the most famous "rubies" in royal collections turned out to be spinel, and for a long time the gem was simply a footnote in other stones' stories. Today collectors and jewelry lovers have caught on: spinel is hard, brilliant, rarely needs treatment, and comes in a color range that runs from fiery red to electric cobalt blue. This guide explains what to look for, how spinel differs from ruby and sapphire, and how to choose a stone you will wear for decades.
What Is Spinel? The Basics Worth Knowing
Spinel is magnesium aluminum oxide, a mineral in its own right and not a variety of any other gem. It crystallizes in the cubic system, usually as tidy octahedra, which matters for two reasons. First, spinel is singly refractive, so light enters and exits without splitting into two rays. That gives a clean, lively sparkle, and it also means spinel shows no pleochroism, so the color looks the same from every direction. Second, those octahedral crystals shape how the rough is cut and how much weight survives.
On the Mohs scale spinel sits at 8, harder than most gems in the jewelry case and well suited to rings. Its refractive index is typically around 1.718 (the usual range runs from roughly 1.712 to 1.762), and its specific gravity is around 3.6. If you are weighing spinel against other stones, our guide to carat weight versus visual size explains why density changes how large a stone looks at a given weight. Spinel is also an official August birthstone, which we cover alongside peridot in our August birthstone guide.
A Short History: The Ruby That Wasn't
Red spinel and ruby often occur in the same gem gravels, especially in Myanmar's Mogok region, and before modern identification methods they were all simply called rubies. The Black Prince's Ruby, set in the front of Britain's Imperial State Crown, and the Timur Ruby, a historic stone with inscriptions of its former owners, are both red spinels. Gemologists separate the two with a refractometer and a polariscope, because ruby is doubly refractive and spinel is not. For a look at the true ruby side of that story, see our ruby education page.
Spinel Color: Red, Pink, Blue and Beyond
Color is where spinel really shows off. Chromium produces the reds and pinks, from a vivid red to a hot, glowing pink. Cobalt creates the rare and highly prized cobalt blue, while iron and other trace elements contribute violets, lavenders, gray-blues, and the soft purples collectors call "lilac." Spinel also appears in orange, peach, and nearly black.
As with any colored stone, hue, tone, and saturation set the value. Our article on how hue, tone, and saturation work applies directly here. Spinel rewards a closer look at saturation: a vivid, evenly colored stone with a pleasing medium tone will almost always outshine a darker or grayer one. Pink spinels from Tanzania's Mahenge area, first found around 2007, are known for a glowing, almost luminous quality that is a favorite among collectors, and Myanmar remains the classic source for fine reds, pinks, and some blues. If you want to compare colors side by side, browse our red gemstones and blue gemstones.
Clarity and Cut in Spinel
Spinel is often found cleaner than many other colored stones, but expectations still vary by color. Typical features include small octahedral crystal inclusions, sometimes arranged in neat lines or planes. A stone that is eye-clean at normal viewing distance is a reasonable goal in most colors. Our clarity guide covers which inclusions matter and which are simply part of a stone's character.
Because spinel is singly refractive, cutters have freedom in how they orient the rough, and a well-cut stone returns light across the whole face. Look for even brightness, no large dead zones, and good symmetry. Spinel takes a bright polish and works beautifully in ovals, cushions, rounds, and pears. See cushion cut gemstones for a shape that suits spinel's crystal habit, and our cut quality guide for what to look for.
Treatment and Natural vs. Lab-Grown Spinel
One of spinel's big advantages is that fine stones are usually found in their natural state, though some are lightly heated, so treatment is always worth asking about. We state a stone's treatment wherever it is known. Lab-grown spinel also exists and has been made for over a century, so it matters to know which you are buying. Every listing on our site states whether a stone is natural, lab-grown or cultured. For more on how treatment affects value, read Gemstone Treatments Explained, and for the natural versus lab-grown question see our comparison guide.
For a significant purchase, it is wise to ask for an independent laboratory report. Origin can add value for fine stones, but it can only be determined by a laboratory, so treat any unreported origin claim with caution.
How to Tell Spinel from Ruby and Sapphire
Because spinel can look like ruby or sapphire, the difference matters. The two reliable tests are optical: a refractometer shows a single reading for spinel and two for corundum, and a polariscope shows spinel remaining dark as it rotates, apart from occasional strain effects. Spinel also lacks the dichroism of ruby and sapphire. Density helps too, with spinel at about 3.6 versus roughly 4.0 for corundum. None of this is a home test, and a laboratory report is the best way to be certain, but it helps to know why a stone sold as spinel is priced differently from ruby.
Spinel Jewelry: Settings and Wear
At hardness 8 with no cleavage to speak of, spinel is a practical choice for engagement rings, pendants, and everyday pieces. Choose a protective setting if you work with your hands, as you would with any gem. If you want to see how spinel looks in finished form, explore our necklaces, and browse the full range in our spinel collection. Looking for a particular color or size? Our sourcing request page is the place to ask, and you can learn more on our spinel education page.
Frequently Asked Questions
Is spinel a good gemstone for an engagement ring?
Yes. Spinel rates 8 on the Mohs scale, has no cleavage that makes it fragile in normal wear, and takes a bright polish that stays lively over time. As with any ring stone, a protective setting is sensible if you use your hands a lot. You can browse spinel in our spinel collection and see how different shapes sit in a setting.
What is the difference between spinel and ruby?
They are different minerals. Spinel is magnesium aluminum oxide and singly refractive, while ruby is a variety of corundum and doubly refractive. Ruby also shows dichroism, and spinel does not. Spinel is somewhat less dense as well. Red spinel was historically mistaken for ruby, which is why some famous crown jewels turned out to be spinel. Learn more on our ruby education page.
Is spinel usually treated?
Fine spinel is often found in its natural state, though some stones are lightly heated, so it is always worth asking. We state a stone's treatment wherever it is known. If you are weighing a significant purchase, request an independent laboratory report. Our guide to gemstone treatments explains what is normal and what is not.
What color of spinel is most valuable?
Vivid, evenly saturated stones lead the market, with fine reds, hot pinks, and rare cobalt blues among the most sought after. Saturation and a pleasing medium tone matter more than the color name alone, and a grayish or very dark stone is worth less than a vivid one of the same hue. For current availability in each color, see our spinel collection.
Can spinel be lab-grown?
Yes, lab-grown spinel has been made for more than a century, so it is important to know which you are buying. Every listing on our site states whether a stone is natural, lab-grown or cultured. For a deeper look at how the two compare, read our lab-grown vs. natural gemstones guide.
Is spinel a birthstone?
Yes, spinel is an official birthstone for August, alongside peridot and sardonyx. It makes a lovely alternative for anyone who wants a birthstone in a color beyond green, from soft pink to deep red. Our August birthstone guide covers all three stones in detail.
