August is unique among the calendar months for offering three distinct birthstones: peridot, spinel, and sardonyx. This abundance provides individuals born in the eighth month with a diverse palette of colors, historical significance, and gemological properties to choose from. The modern list of birthstones, largely standardized in the United States, has evolved over time, with recent additions reflecting both consumer preference and gemological discovery. Peridot, a gem formed deep within the Earth’s mantle, is celebrated for its vibrant olive-green hue. Spinel, often mistaken for ruby or sapphire throughout history, is prized for its exceptional durability and spectrum of colors. Sardonyx, an ancient and banded variety of chalcedony, carries a legacy of use in cameos and intaglio jewelry. Together, these stones offer a remarkable study in geological formation, historical lore, and practical durability for modern jewelry.
The journey to the current trio of August birthstones illustrates the dynamic nature of gemological tradition. The National Association of Jewelers (now Jewelers of America) established the first official birthstone chart in the United States, creating a standardized list that remains widely referenced. The chart has undergone significant revisions. A major update added alternative stones, and in the 21st century, the American Gem Trade Association added tanzanite as a December birthstone, a change that marked the first alteration to the list in fifty years. For August, spinel was added as an additional birthstone, providing more color options alongside peridot and the traditional sardonyx. This evolution shows how the birthstone list is not static but adapts to include new discoveries and popular gems, ensuring that modern consumers have a broad range of choices.
Geological Formation and Sources
The three August birthstones originate from vastly different geological environments, which directly influences their availability and characteristics.
Peridot is one of the few gemstones formed in the Earth’s mantle rather than in the crust. It crystallizes under extreme heat and pressure, brought to the surface by volcanic activity. This unique origin means that peridot can be found in volcanic rocks and even in meteorites, which are sometimes referred to as “pallasite” and contain gem-quality peridot crystals. Major sources for peridot include Pakistan, Myanmar, and the United States (notably Arizona and New Mexico). The gem’s formation in the mantle also contributes to its relative abundance and affordability compared to other green gems like emerald.
Spinel forms in metamorphic rocks, often in association with minerals like corundum (ruby and sapphire) and chrysoberyl. It is found in a wide range of geological settings, from high-temperature metamorphic deposits to alluvial placers. Historically, some of the finest spinel came from the legendary “Badakhshan” region of Central Asia (now part of Afghanistan and Tajikistan), as well as from Sri Lanka and Burma (Myanmar). The gem’s ability to occur in a wide array of colors, including the coveted red and blue varieties, makes it a geologically fascinating stone. Its formation conditions often lead to the growth of large, flawless crystals, which are highly valued by gem cutters.
Sardonyx is a variety of chalcedony, which is itself a microcrystalline form of quartz. It forms in silica-rich environments, typically in volcanic or sedimentary rocks. The distinctive banding of sardonyx results from successive layers of silica (often impregnated with iron oxides) being deposited over time, creating parallel bands of white, black, orange, red, or brown. This banded structure is what made sardonyx a preferred material for cameos, where artisans could carve into the upper layer to create a design against a contrasting background. Historical sources for fine sardonyx include India and Brazil. Unlike peridot and spinel, sardonyx’s formation is a slower, layered process, resulting in a material that is less about crystalline beauty and more about its unique, banded appearance.
Gemological Properties
Understanding the physical and chemical properties of these stones is crucial for both gemologists and consumers, as it informs their durability, care, and value.
Peridot is the gemological name for the mineral olivine, with the chemical formula (Mg, Fe)₂SiO₄. It is a relatively hard stone, scoring 6.5 to 7 on the Mohs scale of hardness. This makes it durable enough for most jewelry, though it can be susceptible to scratching if worn daily against harder materials. Its most prized color is a rich olive green, and its transparency can range from transparent to translucent. Peridot is not typically treated, as its color is natural. The stone’s clarity is often good, though inclusions are common and can include tiny, dark mineral crystals or “lily pads” (small, disc-shaped cavities).
Spinel is a magnesium aluminium oxide (MgAl₂O₄) and is one of the most durable gemstones, with a hardness of 8 on the Mohs scale. This exceptional hardness, combined with its lack of cleavage and good toughness, makes spinel highly resistant to abrasion and breakage. It is considered an excellent choice for rings and bracelets that will undergo daily wear. Spinel occurs in virtually every color of the spectrum, with red and blue being the most valuable. Its refractive index is high, giving it a bright, lively appearance when properly cut. Unlike many gems, spinel is rarely treated, and its color is almost always natural. Its durability and beauty have led some to call it the “perfect birthstone.”
Sardonyx is a composite mineral, primarily composed of silicon dioxide (SiO₂), with a hardness of 6.5 to 7 on the Mohs scale. Its banded structure is its defining characteristic. While it is durable enough for jewelry, its lower hardness compared to spinel means it requires more care to avoid scratches. Sardonyx is often cut into cabochons or beads to highlight its bands. It is not typically treated, and its value is more associated with the quality of its banding and its use in artistic carvings rather than its intrinsic gemological rarity.
Durability Comparison of August Birthstones
The following table summarizes the key gemological properties relevant to jewelry wear and care, based on the provided information.
| Gemstone | Chemical Composition | Mohs Hardness | Key Properties | Suitability for Jewelry |
|---|---|---|---|---|
| Peridot | (Mg, Fe)₂SiO₄ | 6.5 - 7 | Vibrant olive-green color; often found in volcanic rocks. | Good. Durable for most jewelry, but protect from hard impacts. |
| Spinel | MgAl₂O₄ | 8 | Exceptionally hard and tough; occurs in many colors (red, blue, etc.). | Excellent. Highly durable, suitable for any jewelry type, including rings. |
| Sardonyx | SiO₂ (microcrystalline) | 6.5 - 7 | Banded chalcedony; often used for cameos and beads. | Good. Durable, but its banding may be vulnerable to scratching; best for protected settings. |
History and Lore
Each of the August birthstones carries a rich historical narrative, from ancient talismans to symbols of modern status.
Peridot has been prized for over 3,000 years. It was known to ancient Egyptian civilizations, who called it the “gem of the sun.” The Egyptians mined peridot on the island of Zabargad (now St. John’s Island) in the Red Sea, a source that was lost for centuries and then rediscovered in the 20th century. Peridot was believed to protect against nightmares and was often set in gold for the pharaohs. In medieval times, it was used to decorate churches and was thought to have the power to dispel melancholy and bring joy. Its association with light and protection has been a consistent theme throughout history.
Spinel has a long and often misunderstood history. For centuries, the most famous red spinels were mistaken for rubies. The most notable example is the “Black Prince’s Ruby,” a massive red spinel that is part of the British Crown Jewels. It was given to Edward, the Black Prince, in 1367 and has been worn by English monarchs for centuries. Similarly, the “Timur Ruby” is another large red spinel. These historical mix-ups occurred because spinel and ruby (corundum) can form in similar geological environments and look alike. It was only in the 18th century that spinel was recognized as a distinct mineral. Despite this, spinel has always been valued for its beauty and durability, and its inclusion as an August birthstone acknowledges its long-standing place in jewelry history.
Sardonyx is one of the oldest gemstones used in jewelry and carving. Its use dates back to ancient Mesopotamia, Egypt, and Greece, where it was favored for signet rings, cameos, and intaglios. The Romans, in particular, used sardonyx for seals and amulets, believing it offered protection. The layered nature of sardonyx made it ideal for cameos, where a white layer is carved to create a figure against a darker background. This technique was perfected in ancient Greece and Rome and saw a revival during the Renaissance. In ancient lore, sardonyx was associated with strength, courage, and eloquence, and was worn by orators and warriors.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these stones have been imbued with symbolic meanings and metaphysical properties across various cultures.
Peridot is traditionally associated with light, protection, and healing. Its vibrant green color links it to the heart chakra in some modern metaphysical systems, symbolizing emotional balance and compassion. Historically, it was believed to ward off evil spirits and protect the wearer from harm. Its connection to the sun and its radiant glow have made it a symbol of renewal and growth.
Spinel is often associated with revitalization and energy. Its durability is metaphorically linked to the strength and resilience of the wearer. The red variety is connected to passion and vitality, while blue spinel is linked to calm and communication. In some traditions, spinel is believed to inspire hope and alleviate sadness, making it a stone of optimism.
Sardonyx, with its banded structure, symbolizes unity and harmony. It has been historically linked to courage, strength, and protection. In ancient Rome, it was a stone of warriors and was believed to bring victory and shield the bearer from harm. Its use in cameos also ties it to artistic expression and personal identity. In modern crystal healing, it is sometimes used to enhance self-confidence and provide stability.
Care and Cleaning
Proper maintenance is essential to preserve the beauty and longevity of any gemstone jewelry. The care requirements for the August birthstones are dictated by their physical properties.
Peridot (Mohs 6.5-7) requires moderate care. It can be cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as the vibrations could potentially damage the stone, especially if it has internal fractures. It is also sensitive to sudden temperature changes. To protect peridot from scratches, it is best stored separately from harder gems like diamonds or sapphires.
Spinel (Mohs 8) is one of the easiest gemstones to care for due to its exceptional hardness and toughness. It can be safely cleaned with warm, soapy water, a soft brush, and even an ultrasonic cleaner. Its durability makes it resistant to most chemicals and physical damage, making it an ideal choice for everyday jewelry like engagement rings.
Sardonyx (Mohs 6.5-7) is relatively durable but should be handled with care. Clean it with warm, soapy water and a soft cloth or brush. Avoid harsh chemicals and extreme temperatures, which could affect the dye used in some treated varieties (though natural sardonyx is typically untreated). As a banded stone, it is best stored in a soft pouch to prevent the bands from being scratched or chipped.
Conclusion
The trio of August birthstones—peridot, spinel, and sardonyx—offers a remarkable range of options for those born in the eighth month. Peridot provides a vibrant, natural green from deep within the Earth; spinel delivers unmatched durability and a spectrum of colors, including the historically prized red and blue; and sardonyx offers a link to ancient artistic traditions with its distinctive banded patterns. Their collective history spans millennia, from Egyptian talismans and Roman cameos to the crown jewels of Europe. For the modern consumer, these stones are not only beautiful but also practical, with spinel standing out for its hardness and peridot for its affordability and unique origin. Whether chosen for its color, its historical significance, or its durability, the August birthstone trio ensures that every individual can find a gem that resonates with their personal style and story.