Spinel: The August Birthstone That Fooled Royalty for Centuries

Spinel is a naturally occurring magnesium aluminum oxide mineral and the second official August birthstone, added by the American Gem Trade Association in 2016 alongside peridot. It comes in red, pink, cobalt blue, lavender, gray, and black, rates 8 on the Mohs hardness scale, and is almost never treated. Fine red spinels from Mogok, Myanmar, fooled monarchs for centuries by passing as rubies in royal crown jewels.

Spinel has one of the most fascinating stories in the entire gemstone world. For centuries, the most celebrated "rubies" on Earth were not rubies at all. They were spinels. Kings, emperors, and conquerors wore them in crowns and battle helmets, believing they possessed the finest rubies money could buy. It was not until modern gemology developed in the late 1700s and early 1800s that scientists realized spinel was its own distinct mineral species. That revelation rewrote history and, in many ways, made spinel even more intriguing than the stone it had been impersonating.

In 2016, the American Gem Trade Association and Jewelers of America officially added spinel as a second August birthstone alongside peridot. For those of us who have been sourcing and collecting spinel for years, it was a long overdue recognition. I first fell in love with spinel at a Tucson gem show more than a decade ago, when a dealer handed me a two-carat hot pink Mahenge spinel that practically glowed under the display lights. I remember thinking, "How does a stone this beautiful not have a bigger following?" Since then, I have sourced spinel at shows in Tucson, Las Vegas, and Jaipur, India, and my appreciation for this stone grows with every trip. Spinel combines exceptional brilliance, outstanding hardness, and a color range that rivals sapphire, all while remaining one of the most undervalued fine gemstones in the market.

A History of Mistaken Identity

The story of spinel and ruby is one of gemology's greatest tales of mistaken identity. For most of recorded history, any red gemstone with sufficient hardness and brilliance was called a ruby. Red spinels mined alongside rubies in the gem gravels of Myanmar, Sri Lanka, and Central Asia were simply grouped under the category of "balas rubies," a term that referenced the Badakhshan region in present-day Tajikistan and Afghanistan where many of these stones originated. Nobody questioned the classification because the two stones looked remarkably similar to the naked eye and often came from the same deposits.

The most famous example sits in the British Imperial State Crown. The Black Prince's Ruby, a magnificent 170-carat polished red gemstone set prominently at the front of the crown, is not a ruby. It is a red spinel. This stone has been in the possession of English monarchs since the 14th century, when Edward, the Black Prince, received it from Pedro of Castile in 1367. Henry V reportedly wore it on his helmet at the Battle of Agincourt in 1415. For more than 600 years, it was treasured as one of the greatest rubies in the world. The Timur Ruby, another famous stone in the British Crown Jewels, is also a spinel. It weighs 352 carats and bears the inscribed names of Mughal emperors who owned it, including Shah Jahan, the emperor who built the Taj Mahal.

It was not until mineralogist Jean Baptiste Louis Rome de Lisle began systematically classifying minerals in the late 18th century that spinel was identified as a distinct species. Ruby is a variety of corundum (aluminum oxide), while spinel is magnesium aluminum oxide. They share similar hardness and can display identical colors, but their crystal structures are fundamentally different. Ruby forms hexagonal crystals, while spinel forms cubic (isometric) crystals, often as perfect octahedra that gem enthusiasts call "spinel twins." Far from diminishing these historic stones, their identification as spinel adds another layer of fascination. These are gems so beautiful they fooled the most powerful people on Earth for centuries.

Spinel Colors and Varieties

One of spinel's greatest strengths is its remarkable color range. While red spinel gets the most attention due to its historical connection to ruby, this gemstone occurs in virtually every color, and several of those colors are among the most exciting in the entire gem world.

Red Spinel: The classic. Fine red spinel displays a pure, vivid red that can rival the best Burmese rubies. The most prized reds come from Mogok, Myanmar, where spinel has been mined alongside ruby for centuries. These stones exhibit a rich, saturated crimson with just enough warmth to make them glow. Top-quality red spinel in sizes above two carats is genuinely rare and commands serious prices at auction. The difference between a fine red spinel and a fine ruby is nearly impossible to detect without gemological instruments, which is precisely why the confusion lasted for centuries.

Pink and Hot Pink Spinel: Pink spinel is one of the most popular varieties in today's market, and for good reason. The range extends from soft baby pink to an electrifying hot pink that draws attention across a room. The hot pink spinels from Mahenge, Tanzania, are particularly famous for their neon-like saturation and incredible luminosity. When you hold a fine Mahenge hot pink spinel up to the light, it seems to radiate color from within. These stones have created enormous excitement in the gem trade over the past fifteen years and remain highly coveted by collectors and jewelry designers alike.

Cobalt Blue Spinel: If hot pink spinel is exciting, cobalt blue spinel is electric. Found primarily in Vietnam's Luc Yen district and parts of Tanzania, cobalt blue spinel displays a vivid, intensely saturated blue that is caused by trace amounts of cobalt in the crystal structure. The best examples show a neon-like blue that is unlike anything else in the gem world. Cobalt blue spinels are extremely rare, especially in sizes above one carat, and they have become some of the most sought-after colored gemstones among serious collectors. Their color is distinctly different from blue sapphire, with a brighter, more electric quality that makes them instantly recognizable.

Lavender and Violet Spinel: Lavender spinel offers a soft, romantic purple with a gentle pastel quality that makes it perfect for feminine jewelry designs. Violet spinel is deeper and richer, sometimes showing flashes of red or blue depending on the lighting. Both varieties are found primarily in Sri Lanka and Myanmar, and they offer an elegant alternative to amethyst with significantly greater hardness and brilliance.

Black Spinel: On the opposite end of the spectrum, black spinel has become one of the most popular gemstones for modern, everyday jewelry. Its deep, opaque black color and excellent hardness make it a sophisticated alternative to black onyx or black diamond. I have written a detailed guide on black spinel that covers everything from styling to sourcing, and it remains one of the most versatile gemstones in any collection.

Gray Spinel: Gray spinel is an emerging favorite in contemporary jewelry design. These steely, sophisticated stones offer a modern, neutral aesthetic that works beautifully in both minimalist and statement pieces. Fine gray spinel with good transparency and a cool, even tone has been gaining traction among designers who appreciate its understated elegance.

Color-Changing Spinel: Among the rarest varieties, color-changing spinel shifts hue depending on the light source, typically appearing blue or violet in daylight and shifting to purple or pinkish under incandescent light. These stones are collector's treasures, extremely rare and endlessly fascinating to observe.

Where Spinel Comes From

Spinel forms in metamorphic rocks, particularly marble and gem-bearing gravels, and several regions around the world produce stones of exceptional quality. Each source has its own character, and experienced buyers often develop preferences for spinels from specific origins.

Myanmar (Mogok): The Mogok Valley in upper Myanmar is the most historic and revered source of fine spinel. This region, often called the "Valley of Rubies," has produced gem-quality spinel for centuries alongside its famous rubies and sapphires. Mogok spinels are prized for their vivid red and pink colors, exceptional clarity, and a distinctive fluorescence that gives them an inner glow. The finest Mogok red spinels are considered the benchmark against which all other red spinels are measured. Mining in Mogok is small-scale and artisanal, which contributes to the rarity and prestige of stones from this origin.

Sri Lanka: Sri Lanka has been a source of fine gemstones for over 2,000 years, and spinel is no exception. The gem gravels of Ratnapura and surrounding areas produce spinel in an extraordinarily wide range of colors, including blue, pink, violet, and the prized color-changing variety. Sri Lankan spinels tend to have excellent clarity and are often found in larger sizes than those from other sources. The island's alluvial deposits yield gems that have been tumbled and sorted by nature over millions of years, resulting in clean, well-formed crystals.

Tanzania (Mahenge): The Mahenge region in central Tanzania burst onto the gem scene in 2007 when miners discovered a pocket of incredibly vivid hot pink and red spinels that sent shockwaves through the gem trade. These Mahenge spinels displayed a neon-like fluorescent quality that was unlike anything the market had seen before. Prices skyrocketed almost overnight, and Mahenge became synonymous with the finest hot pink spinel in the world. While the initial discovery pocket has largely been mined out, the region continues to produce exceptional stones, and "Mahenge spinel" has become a term that immediately signals top-tier quality to collectors and dealers.

Vietnam (Luc Yen): The Luc Yen district in northern Vietnam is the primary source of coveted cobalt blue spinel. These stones owe their vivid blue color to trace amounts of cobalt, and the finest examples display a neon intensity that is unmatched by any other blue gemstone. Vietnam also produces excellent red, pink, and violet spinels. The mines in Luc Yen are often located in remote, mountainous terrain, and much of the mining is done by hand, which adds to both the romantic origin story and the difficulty of obtaining these stones in quantity.

Tajikistan (Kuh-i-Lal): The Kuh-i-Lal mines in the Pamir Mountains of Tajikistan are the historic source of the "balas rubies" that gave spinel its centuries-long association with ruby. This remote, high-altitude mining area has produced pink and red spinels for over a thousand years. Stones from Kuh-i-Lal were traded along the Silk Road and ended up in the treasuries of Mughal emperors, Persian shahs, and European monarchs. Today, mining continues on a small scale, and Tajik spinels remain prized for their historic provenance and fine pink to red colors.

How to Evaluate Spinel Quality

Evaluating spinel follows the same fundamental principles as any colored gemstone, with color being the dominant factor in determining value. According to Gemological Institute of America grading criteria, color saturation, hue, and tone are the primary value drivers across all colored stones, and spinel rates 8 on the Mohs hardness scale per International Gem Society classification. Spinel also has some unique characteristics that make it especially rewarding to evaluate and collect.

Color: Color is the single most important value factor for spinel. The most valuable spinels display vivid, highly saturated colors with an even distribution throughout the stone. For red spinel, the ideal is a pure, vivid red without brown or orange secondary hues, comparable to the finest Burmese rubies. For pink spinel, the market prizes intense, saturated hot pinks over lighter pastels. Cobalt blue spinels command the highest per-carat prices when they display that characteristic neon blue saturation. Across all colors, the key quality indicators are saturation (how intense the color appears), hue (the actual color and any secondary tones), and tone (how light or dark the stone appears). Spinel's singly refractive nature means it does not display the color doubling or "sleepy" appearance that can affect some doubly refractive stones, resulting in a clean, crisp color presentation.

Clarity: One of spinel's great advantages is that it is typically very clean. Fine spinel often forms with few inclusions, and eye-clean stones are the standard rather than the exception in higher quality material. Unlike ruby and sapphire, where inclusions are common and accepted, the market expects spinel to be clean to the eye. When inclusions are present, they are typically small crystals or fingerprint-like healing features. Eye-clean clarity combined with fine color significantly increases value.

Cut: Spinel responds beautifully to skilled cutting. Because it is singly refractive with a relatively high refractive index (approximately 1.71 to 1.73), well-cut spinel displays excellent brilliance and a lively light return. The most common shapes are oval, cushion, and round, though you will also find emerald cuts, pears, and occasionally custom precision cuts that maximize the stone's optical properties. A well-proportioned cut that balances light return with color saturation will always be more valuable than a poorly cut stone of similar material. I pay close attention to cut quality when sourcing spinel because it makes such a noticeable difference in how the stone performs in jewelry.

Carat Weight: Fine spinel becomes exponentially rarer as size increases. Stones under one carat in good quality are relatively accessible, but once you move above two to three carats in top colors, availability drops sharply and prices per carat increase significantly. Fine red and cobalt blue spinels above five carats are genuinely rare and can command prices comparable to or exceeding fine rubies and sapphires of similar size. The sweet spot for most collectors is the one-to-three-carat range, where you can find exceptional quality at prices that still represent strong value relative to comparable colored gemstones.

Durability: Spinel rates 8 on the Mohs hardness scale, placing it just below corundum (ruby and sapphire at 9) and well above most other colored gemstones. It has no cleavage, meaning it does not have weak planes along which it might split, and it has good toughness overall. This combination of hardness, lack of cleavage, and toughness makes spinel an excellent choice for all types of jewelry, including rings that will see daily wear. It is one of the most durable colored gemstones available.

Spinel vs Ruby

Given their intertwined history, comparing spinel and ruby is natural, and the comparison reveals why spinel deserves far more recognition than it currently receives. Both can display vivid red colors that are virtually indistinguishable to the naked eye, but the two stones differ in several important ways.

Optical Properties: Ruby is doubly refractive, meaning light splits into two rays as it passes through the crystal. Spinel is singly refractive, meaning light passes through without splitting. In practical terms, this gives spinel a cleaner, crisper appearance, particularly in lighter tones where doubling can sometimes create a slightly fuzzy look in ruby. Spinel's single refraction also contributes to its bright, direct brilliance.

Treatment: This is where the comparison becomes especially compelling. The vast majority of rubies on the market today have been heat-treated to improve their color and clarity. Heat treatment is so standard in the ruby market that untreated rubies of fine quality command significant premiums, sometimes two to five times the price of comparable treated stones. Spinel, by contrast, is almost never treated. The colors you see in spinel are natural, straight from the earth, with no human enhancement. For collectors who value natural, untreated gemstones, this is a major differentiator.

Rarity: While ruby is rarer overall in gem-quality material, fine red spinel in sizes above two to three carats is actually rarer than fine ruby in equivalent sizes. The global supply of top-quality red spinel is extremely limited, with only a handful of sources producing stones of the highest caliber. As more collectors and gem enthusiasts learn about spinel, demand continues to rise against this limited supply.

Value: Fine red spinel offers what I consider one of the best value propositions in the colored gemstone market. A high-quality, untreated red spinel will typically cost significantly less than a comparable untreated ruby, despite being rarer in many size categories and requiring no treatment to achieve its color. For buyers who want a vivid red gemstone with exceptional brilliance, outstanding durability, and complete confidence that the color is natural, spinel delivers all of that at a fraction of what a comparable untreated ruby would cost. This value gap will not last forever as awareness grows.

Spinel Style Archetypes in the Ulka Rocks Collection

Spinel jewelry in the Ulka Rocks collection groups into three style archetypes that match how collectors actually wear and layer the stone. Inventory rotates seasonally as Ulka sources at premier trade shows including Tucson and JCK Las Vegas. Loose colored spinel pricing varies widely by color: black spinel finished pieces run roughly $95 to $800, while fine red and pink spinel typically trades at $300 to $2,000 per carat in loose stones.

For ready-to-ship pieces, browse the Black Spinel Collection, or explore the full collection to see current colored spinel inventory.

Styling Spinel Jewelry

Spinel's combination of vivid color, excellent hardness, and wide variety makes it one of the most versatile gemstones for jewelry design. Its 8 on the Mohs scale means it performs beautifully in rings, which is important because that is where many people want to wear their finest colored stones.

Red and Pink Spinel: Red and pink spinels look stunning in warm gold settings. Yellow gold enhances the warmth of red spinel and creates a classic, regal look that echoes the stone's royal history. Rose gold pairs particularly well with pink spinel, creating a harmonious, feminine aesthetic that works for both engagement rings and cocktail pieces. For a more contemporary look, a vivid pink spinel in a simple solitaire setting makes a powerful statement that needs no embellishment. I love pairing hot pink spinel with diamond accents in rose gold for pieces that feel modern but timeless.

Cobalt Blue Spinel: The electric blue of cobalt spinel demands a metal that lets the color take center stage. White gold and platinum are the natural choices, providing a cool, neutral backdrop that amplifies the stone's neon intensity. A cobalt blue spinel flanked by small white diamonds in a three-stone ring is one of the most striking pieces of jewelry you will ever see. Because cobalt blue spinels tend to be smaller due to their rarity, they also work beautifully as accent stones or in cluster designs where their vivid color creates focal points.

Black Spinel: Black spinel is the everyday hero of spinel jewelry. Its deep black color, excellent hardness, and affordability make it perfect for pieces you wear daily: tennis bracelets, stud earrings, beaded necklaces, and stackable rings. Black spinel pairs effortlessly with both gold and silver, and it complements virtually every wardrobe and skin tone. It is the stone I recommend most often to customers who want sophisticated, versatile pieces they can wear from morning meetings to evening events.

Layering and Stacking: Spinel's range of colors makes it ideal for creative layering. A beaded necklace combining black spinel with hot pink spinel accents creates a look that is both bold and refined. Stacking rings in different spinel colors allows you to create a personalized rainbow that reflects your individual style. The stone's durability means you do not need to worry about wearing multiple spinel pieces together, as they hold up beautifully to everyday contact.

Caring for Spinel

Spinel is one of the most low-maintenance gemstones you can own, which makes it ideal for jewelry you want to wear regularly rather than keep locked in a safe.

With a hardness of 8 on the Mohs scale, spinel resists scratching from most everyday materials. It has no cleavage planes, which means it is resistant to chipping and breaking along weak structural lines. And unlike some gemstones that can be sensitive to heat, chemicals, or sudden temperature changes, spinel is remarkably stable under normal wearing conditions.

Cleaning spinel is straightforward. Warm water with a mild dish soap and a soft-bristled brush (an old toothbrush works perfectly) is all you need. Gently brush the stone and its setting to remove oils and dust, rinse with clean water, and pat dry with a soft cloth. Ultrasonic cleaners are generally safe for spinel, though I always recommend the gentle hand-washing approach as your default cleaning method for any fine gemstone.

For storage, keep spinel jewelry in individual soft pouches or lined compartments to prevent contact with harder stones like diamond, ruby, or sapphire, which could scratch spinel's surface. Beyond that, there are no special precautions needed. Spinel is genuinely one of the easiest gemstones to care for, and its durability is one of the many reasons I recommend it so enthusiastically.