August Birthstones - The Complete Guide to Peridot, Sardonyx, and Spinel

August is the rare birth month that gives you a genuine choice. Most months have one birthstone, sometimes two. August has three — peridot, sardonyx, and spinel — and they could not be more different from each other. Peridot is the bright lime-green stone everyone associates with August on sight. Sardonyx is layered reddish-brown chalcedony with a 4,000-year history reaching back to Egyptian Pharaohs and Roman soldiers. Spinel is the chameleon of the gemstone world, a stone that has spent most of recorded history being mistaken for ruby in royal crowns. Three stones, three completely different aesthetics, three completely different stories.

As a working jeweler, I get the same questions about August birthstones over and over. Which is the "real" one? Are sardonyx and spinel just consolation prizes for people who don't want peridot? What is sardonyx, exactly? How is spinel different from ruby? Which should I choose for an August baby or a Leo birthday gift? The honest answer to all of these is that each of the three stones is genuinely meaningful on its own terms, and choosing between them is less about ranking and more about which character best fits the person you're gifting (or the person you are).

This guide walks through all three August birthstones with equal care — their histories, their symbolic meanings, their durability and care requirements, the price ranges to expect, and the famous gemological cases each one carries (the Cleopatra "emerald" mystery for peridot, the Hercules-and-Mars Roman talismans for sardonyx, the Black Prince's Ruby revelation for spinel). We will cover the Leo and Virgo zodiac connections, the choose-your-stone framework, and the practical considerations for engagement rings, gifts, and meaningful daily-wear jewelry. By the end you will know which August birthstone fits your situation — and why.

Birthstone tradition has been layered across thousands of years, and August's three stones reflect three different eras of that tradition. Sardonyx is the original — its association with August dates back to ancient Hebrew and Greco-Roman tradition, where birthstones were tied to gemstones in the High Priest's breastplate described in Exodus. Sardonyx appears multiple times in biblical references and was used as an August stone for well over 2,000 years before the modern birthstone list existed.

The modern birthstone list was created in 1912 by the American National Association of Jewelers (now known as Jewelers of America), which formalized one official stone per month for the first time in American jewelry tradition. The 1912 list designated peridot as the August birthstone, codifying a tradition that had been informally observed across Western jewelry for over a century. Peridot quickly became the dominant August stone in popular use, displacing sardonyx in most modern jewelry — though sardonyx retained its status as the traditional alternative.

The list has been updated only three times since 1912. In 1952, alexandrite, citrine, tourmaline, and zircon were added. In 2002, tanzanite was added as a December alternative. In 2016, the American Gem Trade Association (AGTA) and Jewelers of America jointly added spinel as a third August birthstone — the first update in 14 years and one of only four amendments to the modern list in over a century. The 2016 addition recognized spinel's growing popularity and its unique history of having been confused with ruby for centuries. As of 2026, August is one of only three months with three official birthstones, alongside June (pearl, alexandrite, moonstone) and December (turquoise, tanzanite, blue zircon).

Peridot is the gem-quality variety of olivine, a magnesium iron silicate that forms deep in the Earth's mantle and reaches the surface through volcanic activity. The GIA documents that gem-quality peridot has also been found in pallasite meteorites, making it one of the only gemstones with confirmed extraterrestrial origin. Peridot is one of the few gemstones that occurs in only one color — a vivid yellow-green to olive-green produced by the iron content in the crystal structure. Stones with lower iron read brighter and more yellow-green; stones with higher iron read deeper and more olive.

The Egyptians began mining peridot on Zabargad Island (also called St. John's Island, or Topazios in antiquity) in the Red Sea approximately 1500 BC. The GIA confirms peridot's nickname comes from this history: "Peridot has always been associated with light. The Egyptians called it the 'gem of the sun.'" Some historians believe many of Cleopatra's famous "emerald" pieces were actually peridot — the two stones were not reliably distinguished in antiquity. The GIA also documents that the 200-carat "emeralds" adorning the Shrine of the Three Kings in Cologne Cathedral, believed for centuries to be emeralds, are in fact peridots.

Peridot was formalized as the August birthstone in 1912 by the American National Association of Jewelers. Today it is by far the most popular of the three August birthstones — accessible in price, instantly recognizable, and meaningful for its bright, optimistic, forward-moving symbolism. Modern peridot is sourced primarily from Arizona (San Carlos Apache Reservation), Pakistan (Sapat Gali / Suppat in Kohistan), Myanmar, and China. Pakistani peridot is widely regarded as the finest commercially available — exceptional color saturation, larger stone sizes, and high clarity.

Sardonyx is a banded variety of chalcedony — the same cryptocrystalline quartz family that includes moss agate, carnelian, and onyx. What makes sardonyx distinctive is its alternating layers of sard (a reddish-brown to brown form of chalcedony) and onyx (typically white or black layers). The result is a striped or banded stone with clean horizontal divisions between the color zones. The name comes from sard (referring to the ancient city of Sardis, now in Turkey, where the reddish-brown chalcedony was historically mined) and the Greek word onyx, meaning "nail" or "claw."

Sardonyx is the oldest of the August birthstones, with documented use stretching back more than 4,000 years to the Second Dynasty of Egypt. The GIA documents that "sardonyx is believed to be one of the stones in the High Priest's breastplate, as referred to in the Old Testament, and to represent the strength of spiritual life. Roman soldiers wore sardonyx rings with the image of Mars carved on them for protection in battle." Roman seal-makers favored sardonyx for signet rings because hot wax would not stick to the stone — making it ideal for impressing wax seals on documents. Renaissance orators reportedly wore sardonyx believing it would make their speech more persuasive, building on the stone's longstanding association with eloquence.

Symbolically, sardonyx is associated with courage, eloquence, marital stability, and protection. Its banded structure has made it a favorite carving material for cameos and intaglios across history — many museum collections of ancient Mesopotamian and Roman jewelry feature sardonyx pieces, and the stone remains popular today for vintage-inspired cameo jewelry. Modern sardonyx is sourced primarily from Brazil, Germany, Madagascar, India, and the United States. At Mohs 6.5–7, sardonyx is durable enough for engagement rings and daily wear with reasonable care.

Spinel is a magnesium aluminum oxide (MgAl₂O₄) that occurs in a remarkable range of colors — red, pink, purple, blue, orange, and black — produced by trace elements including chromium (red and pink), iron (orange and purple), and cobalt (vivid blue). At Mohs 8, spinel is the hardest of August's three birthstones — harder than peridot and sardonyx, comparable to topaz, and only one step below ruby and sapphire on the hardness scale. This durability makes spinel particularly well-suited to engagement rings and daily-wear jewelry. The name spinel comes from the Latin spina meaning "thorn," referencing the pointed shape of natural spinel crystals — though some etymologies trace it to the Greek spitha (spark) or spinthir (scintillate), referencing the stone's exceptional brilliance.

Spinel's defining historical fact is its centuries-long misidentification as ruby. The GIA documents that "for centuries, spinel was mistaken for other gemstones. Some of history's most famous 'rubies' have actually turned out to be this August birthstone." The most famous example is the Black Prince's Ruby — a 170-carat polished red gem that has sat in Britain's Imperial State Crown since 1367. For nearly 600 years it was believed to be a ruby. Modern gemological analysis identified it as red spinel in the 19th century. The same revelation has applied to the 361-carat Timur Ruby (presented to Queen Victoria in 1851), the 398-carat ruby-colored gem topping the Imperial Crown of Russia, and several major red gems in the Russian, Persian, and English crown jewels. Spinel was not definitively distinguished from ruby until the 18th century — gemologists and mineralogists finally developed the analytical techniques to separate them based on chemical composition (spinel is magnesium aluminum oxide, ruby is aluminum oxide).

Spinel was added to the August birthstone list in 2016 by a joint announcement from the American Gem Trade Association (AGTA) and Jewelers of America. The 2016 update was the first amendment to the modern birthstone list since 2002 (when tanzanite was added to December), and only the fourth amendment since the list was created in 1912. The recognition reflected spinel's growing popularity among gem collectors and the gemological community's longstanding appreciation of the stone — for many gemologists, fine red spinel rivals or exceeds ruby in beauty, and certain large fine red spinels now command prices comparable to fine rubies of equivalent quality.

Leo (July 23 – August 22) is the fixed-fire sign associated with the sun, leadership, confident self-expression, and bold creative energy. The astrological alignment with August's three birthstones is strongest for peridot — the "gem of the sun" connects directly to Leo's solar archetype. Peridot's bright, forward-moving energy and its association with abundance, renewal, and confident clarity all align naturally with Leo's character. Sardonyx also resonates with Leo through its ancient associations with courage and protection — Roman warriors wore sardonyx talismans of Mars and Hercules to channel exactly the kind of bold, brave, leader-of-the-pack energy that defines the Leo archetype. Spinel offers Leo wearers a modern alternative with red spinel's intense, vibrant character matching Leo's bold aesthetic preferences.

Virgo (August 23 – September 22) is the mutable-earth sign associated with analytical thinking, attention to detail, service, and grounded practical wisdom. Virgos born in late August can claim any of the three August birthstones (Virgos born in September align with sapphire instead). Peridot resonates particularly well with Virgo through its association with clarity of purpose, mental sharpness, and the bright forward-moving energy that helps Virgos channel their analytical strengths productively. Sardonyx, with its traditional Renaissance association with eloquence, clear thinking, self-discipline, and persuasive speech, is an especially strong Virgo match — Renaissance orators wore it specifically for these qualities. Spinel, with its grounding root-chakra associations and its earthy mineral character, aligns with Virgo's earth element.

For Leo birthday gifts (late July through August 22), peridot is the most popular and most archetypally-aligned choice, with sardonyx as the bolder traditionalist alternative. For Virgo birthday gifts (August 23 through September), peridot remains popular but sardonyx's eloquence and discipline symbolism makes it a thoughtful Virgo-specific choice. Spinel works well for both signs as a contemporary, distinctive alternative.