The month of August is uniquely represented by three distinct birthstones: Peridot, Sardonyx, and Spinel. This trio offers a remarkable range of colors, histories, and geological origins, making it one of the most diverse months in the birthstone calendar. Peridot, a vibrant green gem formed in the Earth's mantle and found in meteorites, is the most recognized August stone, symbolizing strength and protection. Sardonyx, an ancient and layered chalcedony, carries a legacy of Roman seals and spiritual significance, valued for its durability and carving potential. Spinel, often mistaken for ruby throughout history, has recently gained acclaim as a standalone gemstone with its own rich palette and storied past. This article explores the geology, history, properties, and care of these three captivating August birthstones, drawing from historical records and gemological research.
History and Lore: From Ancient Talismans to Modern Birthstones
The historical journey of the August birthstones is a tapestry of ancient trade, mistaken identity, and cultural symbolism. Peridot, the yellowish-green to greenish-yellow variety of the mineral olivine, has a history of confusion with other gems. Its name derives from the Arabic faridat, meaning "gem." Historical sources note that the Red Sea island of Topazios, which is actually the origin of the name "topaz," was a source of peridot, leading to centuries of misidentification. Furthermore, the 200-carat gems adorning the Shrine of the Three Holy Kings in Germany’s Cologne Cathedral were long believed to be emeralds but are now identified as peridot. Some historians even speculate that Cleopatra’s famed emerald collection may have been composed of peridot. This gem was valued across many ancient and medieval cultures, often linked to the volcano goddess Pele; green peridot crystals found in volcanic ashes were believed to be her tears. When set in gold, peridot was said to protect the wearer from nightmares.
Sardonyx, the original August birthstone, boasts a history dating back more than 4,000 years. This banded variety of chalcedony, composed of alternating layers of sard (a brownish-red to dark orange chalcedony) and onyx (typically white or black chalcedony), was immensely popular in ancient Rome. Its practical use for seals and signet rings stemmed from a unique property: hot wax would not stick to it, making it ideal for imprinting signatures. For millennia, its distinct bands made it a preferred material for carving cameos and intaglios. Sardonyx is also believed to be one of the stones referenced in the High Priest’s breastplate in the Old Testament, representing the strength of spiritual life. Roman soldiers wore sardonyx rings carved with the image of Mars, the god of war, seeking protection in battle. Today, its associations have expanded to include courage, happiness, clear communication, and stability in marriage and partnerships.
Spinel’s history is defined by its long-standing confusion with ruby. For centuries, the most prized red spinels were misidentified as rubies, with many famous "rubies" in royal collections later proven to be spinel. This gemstone, which occurs in a wide spectrum of colors from red and pink to blue and black, was often sourced from the same regions as ruby, such as Burma (Myanmar) and Sri Lanka, further contributing to the mix-up. It wasn't until the 19th century that spinel was formally recognized as a distinct mineral species. Its recent elevation to an official August birthstone in 2016 by the American Gem Trade Association (AGTA) and the Jewelers of America (JA) has brought it out of ruby’s shadow, allowing consumers to appreciate its own unique beauty and history.
The official designation of these stones as August birthstones is a modern development. While peridot and sardonyx have ancient roots as traditional stones, the list was expanded to include spinel to provide more variety and choice. This reflects a broader trend in the birthstone industry to acknowledge the full spectrum of gemstones available today.
Geological Formation and Sources
The three August birthstones originate from vastly different geological environments, showcasing the incredible diversity of mineral formation.
Peridot is unique among gemstones for its formation in extreme conditions. It is the gem variety of olivine, a mineral that makes up a significant portion of the Earth's upper mantle. Peridot can be brought to the surface through volcanic activity, often found in hardened lava flows. Remarkably, it is also one of the few gems found in meteorites that have traveled from outer space to Earth. This extraterrestrial origin adds a layer of wonder to its already fascinating story. Historically, peridot was mined on the Red Sea island of Topazios (now Zabargad). While that source is no longer active, significant commercial sources today include Pakistan, Myanmar, and Arizona in the United States, particularly the San Carlos Apache Reservation, which is known for producing peridot of a vivid yellow-green hue.
Sardonyx, as a variety of chalcedony (a microcrystalline form of quartz), forms in low-temperature environments, typically in cavities within volcanic or sedimentary rocks. The banding characteristic of sardonyx is created by successive layers of sard and onyx deposited over time. India is noted for producing sardonyx with particularly good contrast between its layers, making it highly suitable for carving. Other sources include Brazil, Germany, the Czech Republic, Madagascar, Uruguay, and the United States. Its widespread occurrence makes it a relatively accessible gemstone.
Spinel crystallizes in the metamorphic environment, often forming in magnesium-rich rocks subjected to high heat and pressure. It is commonly found in alluvial deposits, where weathering has released the crystals from their host rock and transported them into riverbeds and plains. Historically, the most famous spinel deposits were in Burma (Myanmar), particularly the Mogok region, which produced the renowned "Black Prince's Ruby" (actually a red spinel) in the British Crown Jewels. Sri Lanka is another historic source for spinel, especially for red and pink varieties. Other localities include Vietnam, Afghanistan, and Pakistan. The gem can also occur in contact zones around intrusions of magma into carbonate rocks.
Gemological Properties
Understanding the physical and optical characteristics of these stones is crucial for identification, valuation, and care. The following table summarizes key gemological data for the August birthstones based on available information.
| Property | Peridot | Sardonyx | Spinel |
|---|---|---|---|
| Mineral Species | Olivine | Chalcedony (Quartz) | Spinel |
| Chemical Formula | (Mg,Fe)₂SiO₄ | SiO₂ | MgAl₂O₄ |
| Crystal System | Orthorhombic | Hexagonal (microcrystalline) | Cubic |
| Hardness (Mohs) | 6.5 - 7 | 6.5 - 7 | 8 |
| Refractive Index | 1.64 - 1.69 | 1.53 - 1.54 | 1.71 - 1.76 |
| Specific Gravity | 3.34 - 3.48 | 2.60 - 2.64 | 3.58 - 3.61 |
| Color Range | Yellowish green to greenish yellow | Bands of brownish-red to dark orange (sard) with white or black (onyx) | Wide spectrum: red, pink, orange, purple, blue, black, colorless |
| Transparency | Transparent to translucent | Opaque to translucent | Transparent to translucent |
| Notable Traits | Can be found in meteorites; often confused with emerald. | Banded structure; popular for carving cameos and intaglios. | Often mistaken for ruby; high refractive index and brilliance. |
Peridot is a relatively hard gem, making it suitable for various jewelry types, though care is needed to avoid scratches. Its most prized color is a rich olive-green, though it can vary depending on its iron content. It is typically found in faceted cuts to enhance its brilliance.
Sardonyx, with a hardness of 6.5 to 7 on the Mohs scale, is durable enough for daily wear but should be protected from sharp blows. Its value and beauty are heavily dependent on the distinctness and regularity of its banding. It is most commonly cut en cabochon to showcase its layers or carved into intricate cameos and intaglios. A notable characteristic is that sardonyx, like other forms of chalcedony, is frequently dyed to enhance or create its banding. This treatment is sensitive to high heat, which can alter the color.
Spinel is the hardest of the three August stones, with a Mohs hardness of 8. This makes it exceptionally durable and resistant to scratching, ideal for rings and bracelets worn daily. It exhibits a high refractive index and strong brilliance, often rivaling that of ruby and sapphire. Its color range is exceptionally broad; while red is the most valuable, blue and pink spinels are also highly sought after. The gem is typically found in faceted forms to maximize its sparkle and color saturation.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each August birthstone carries a wealth of symbolic meaning and metaphysical lore, accumulated over centuries of human use and belief.
Peridot is widely associated with strength. Its lore is deeply connected to nature and the elements, from the volcanic tears of Pele to its extraterrestrial origins. It is believed to ward off negative energies and nightmares, especially when set in gold. Its green color, reminiscent of nature, symbolizes growth, renewal, and prosperity. In modern crystal healing, peridot is often linked to the heart chakra, promoting emotional balance and openness to love and forgiveness.
Sardonyx is traditionally a stone of courage, strength, and protection. Its historical use by Roman soldiers as a talisman against harm underscores this association. It is also believed to enhance clear communication and bring stability to relationships, making it a popular stone for couples. The stone is said to foster happiness and integrity, aligning with its historical role in signet rings—symbols of personal authority and promise.
Spinel, while newer to the modern birthstone list, has accumulated its own symbolism. Its resilience and hardness make it a symbol of endurance and vitality. The vibrant red varieties are linked to passion and energy, while the calming blue and pink shades are associated with tranquility and affection. As a stone that was long mistaken for ruby, it is also seen as a symbol of authenticity—a reminder to recognize and value one's own unique qualities.
Care and Cleaning
Proper maintenance is essential to preserve the beauty and longevity of these gemstones. Their differing physical properties dictate specific care instructions.
Peridot (Hardness 6.5-7) requires moderate care. It can be cleaned safely with warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as the vibrations could cause fractures if the stone has inclusions. Steam cleaning is also not recommended. Store peridot jewelry separately to prevent scratching by harder gems like sapphire or diamond.
Sardonyx (Hardness 6.5-7) shares similar care guidelines with peridot. Warm, soapy water and a soft brush are the best methods for cleaning. Crucially, because sardonyx is often dyed, ultrasonic and steam cleaners should be used with extreme caution or avoided entirely, as heat and vibrations can damage the dye or alter the stone's color. High heat during jewelry manufacturing or repair can also affect dyed sardonyx.
Spinel (Hardness 8) is the most durable of the three and is relatively easy to care for. It can be cleaned with warm, soapy water, a soft brush, and even an ultrasonic cleaner (provided the piece has no fractures or inclusions). However, as with any gemstone, it is best to avoid sudden temperature changes and harsh chemicals. Its high durability makes it an excellent choice for jewelry that will be worn frequently.
Conclusion
The August birthstones—Peridot, Sardonyx, and Spinel—offer a compelling trio that spans the spectrum of gemological and historical experience. From the extraterrestrial origins and volcanic lore of Peridot to the ancient, carved legacy of Sardonyx and the rediscovered brilliance of Spinel, each stone provides a unique narrative. Their shared characteristics of durability and captivating color make them not only meaningful symbols for those born in August but also enduring treasures in the world of gemology. Understanding their distinct properties, histories, and care requirements allows enthusiasts and collectors to fully appreciate the depth and diversity these gems bring to the birthstone tradition.