The month of August is uniquely represented by three distinct birthstones: peridot, spinel, and sardonyx. This trio offers a remarkable spectrum of color, from the vibrant olive-green of peridot to the fiery reds of spinel and the banded patterns of sardonyx. Each stone carries a deep history, unique geological origins, and specific gemological properties that appeal to collectors, jewelers, and those born in the eighth month. This article explores the characteristics, lore, and care of these three gems, providing a comprehensive guide to the birthstones of August.
History and Lore: From Ancient Seals to Modern Revival
The history of August's birthstones spans millennia, with each stone playing a different role in human culture. Sardonyx is the most ancient of the trio, with a history dating back more than 4,000 years. It is a combination of two types of chalcedony (cryptocrystalline quartz): sard and onyx. Bands of brownish red to brown to dark orange sard alternate with typically white or black layers of onyx. In ancient times, sardonyx was a popular stone for Roman seals and signet rings, as hot wax would not stick to it. Its use in carving and intaglio work made it a valued material for creating personal insignia and amulets.
Peridot has a long and often misunderstood history. The word “peridot” comes from the Arabic faridat, meaning gem. Throughout history, peridot has often been confused with other gems such as topaz and emerald. The Red Sea island of Topazios, a purported source of the name “topaz,” actually produced peridot. The Shrine of the Three Holy Kings in Germany’s Cologne Cathedral is decorated with 200 carats of gems that were believed to be emeralds but are, in fact, the August birthstone peridot. Some historians even speculate that Cleopatra’s famous emerald collection may have been comprised of peridot. This gem was valued in many ancient and medieval cultures, and its formation under extreme conditions—found in hardened lava from Earth’s mantle and in meteorites from outer space—adds to its mystique.
Spinel was historically underappreciated, often mistaken for ruby. For centuries, red spinel was confused with its more famous counterpart, a confusion that persisted until modern gemological science could distinguish the two. This mistaken identity meant that many historical "rubies" were, in fact, spinels. The gem has gained significant appreciation in recent times as consumers seek alternatives to ruby, and its own vibrant colors—red, pink, blue, and purple—are now celebrated for their unique beauty. A 2007 discovery in Tanzania of pinkish and orangy red spinel captivated gem collectors, highlighting the stone's renewed status.
The modern standardization of birthstones began with the National Association of Jewelers (now Jewelers of America), which established the first official birthstone chart in the United States. Spinel was officially added as an additional birthstone for August, providing more color options alongside peridot and sardonyx. This addition marked a significant update, acknowledging spinel's distinct identity and gemological value.
Geological Formation and Sources
The three August birthstones originate from vastly different geological processes and are mined in specific regions around the world.
Peridot is the gem variety of the mineral olivine. Its formation is particularly unique. It can be found in the hardened lava that carried it from deep within Earth’s mantle, a process that brings the gem to the surface in volcanic regions. Remarkably, peridot is also found in meteorites that traveled from outer space, making it one of the few gems formed in extraterrestrial environments. Major sources of peridot include the San Carlos Apache Reservation in Arizona, which is a significant producer of commercial-grade peridot. Other notable sources include Pakistan, Myanmar, and the Red Sea island of Zabargad (Topazios), which was a historical source of the gem.
Spinel is formed in metamorphic rocks and in alluvial deposits. The Luc Yen region in northern Vietnam has produced this August birthstone in deep red, purple, pink, and violet-blue since the 1980s, and vivid blue spinels were found there in the 2000s. Getting to the mines requires a five- to six-hour drive from Hanoi and then hiking or biking for several more hours. A 2007 discovery in Tanzania of pinkish and orangy red spinel also captivated gem collectors, and mines there produce the August birthstone in purple and blue hues. Other sources include Sri Lanka and Tajikistan.
Sardonyx is a variety of chalcedony, which is a cryptocrystalline form of quartz. It forms in volcanic and sedimentary environments, where silica-rich solutions deposit layers in rock cavities. While specific modern mining locations are not detailed in the sources, its historical use suggests it was sourced from regions around the Mediterranean and Middle East, where chalcedony deposits are common.
Gemological Properties
Understanding the physical and chemical properties of these gems is essential for their identification, valuation, and care. The following table summarizes key gemological data for the three August birthstones, based on the provided sources.
| Property | Peridot | Spinel | Sardonyx |
|---|---|---|---|
| Mineral Family | Olivine | Spinel | Chalcedony (Quartz) |
| Chemical Formula | (Mg, Fe)₂SiO₄ | MgAl₂O₄ | SiO₂ |
| Color | Olive-green to yellowish-green | Red, pink, blue, purple, black | Bands of brownish red, brown, dark orange with white or black |
| Mohs Hardness | 6.5 – 7 | 8 | 6.5 – 7 |
| Crystal System | Orthorhombic | Cubic | Hexagonal (microcrystalline) |
| Refractive Index | Not specified in sources | Not specified in sources | Not specified in sources |
| Durability | Fair to good; can be brittle | Excellent; very durable | Fair; can be prone to chipping |
Peridot has a hardness of 6.5 to 7 on the Mohs scale, making it suitable for most jewelry but requiring some care to avoid scratches. Its color ranges from yellowish green to greenish yellow, and its chemical composition is (Mg, Fe)₂SiO₄.
Spinel is notably durable, with a hardness of 8 on the Mohs scale. This makes it an excellent choice for rings and other jewelry that undergoes daily wear. Its cubic crystal system and chemical formula, MgAl₂O₄, distinguish it from ruby (corundum, Al₂O₃). Spinel exhibits a wide color range, including red, pink, blue, purple, and black.
Sardonyx, as a variety of chalcedony, has a hardness of 6.5 to 7. It is characterized by its distinct banding of sard (brownish-red to brown) and onyx (typically white or black). Its microcrystalline structure gives it a waxy luster and makes it suitable for carving.
Symbolism and Metaphysical Beliefs
Each of the August birthstones carries a rich tapestry of symbolism and metaphysical beliefs, reflecting their historical and cultural significance.
Peridot is often associated with renewal, growth, and prosperity. Its vibrant green color connects it to nature, vitality, and the heart. Historically, it was believed to ward off evil spirits and protect against nightmares. Its formation in extreme conditions—deep within the Earth and from outer space—has led to associations with strength and resilience. The gem is also linked to positive energy and the attraction of good fortune.
Spinel symbolizes revitalization and energy. Its historical confusion with ruby has imbued it with some of ruby's traditional meanings, such as passion and protection, but spinel is also celebrated for its own attributes of renewal and harmony. The variety of colors in spinel allows for different symbolic associations: red for passion, blue for calm and clarity, and pink for love and compassion. Its durability symbolizes steadfastness and longevity.
Sardonyx, as the most ancient of the August stones, carries symbolism deeply rooted in history. It was believed to provide protection, courage, and eloquence. In ancient Rome, it was a stone of warriors and orators, used for seals and amulets to ensure victory in battle and persuasive speech. Its banded structure represents balance and harmony, and it is often associated with stability and happiness in relationships. The stone is thought to foster a sense of security and groundedness.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones. The care instructions are directly tied to their gemological properties, particularly their hardness and stability.
Peridot requires careful handling due to its hardness of 6.5 to 7 and its potential brittleness. It is advisable to clean peridot jewelry using warm soapy water and a soft brush. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone or its settings. Store peridot separately from harder gems to prevent scratches.
Spinel is one of the most durable of the birthstones, with a hardness of 8. It is stable when exposed to light and most chemicals. Ultrasonic and steam cleaners can generally be used, but caution is advised if the stone has fractures, as the vibrations could cause damage. Warm soapy water is always a safe alternative. However, high heat can cause some colors of spinel to fade, so it should be kept away from intense heat sources.
Sardonyx, with a hardness of 6.5 to 7, is relatively durable but can be prone to chipping due to its layered structure. It should be cleaned with warm soapy water and a soft brush. Avoid ultrasonic cleaners, as the vibrations may loosen the stone or damage its settings. As a form of quartz, it is generally stable under normal conditions but should be protected from sharp blows and extreme temperature changes.
Conclusion
The August birthstones—peridot, spinel, and sardonyx—offer a diverse and fascinating array of options for those born in this month. From the ancient, banded elegance of sardonyx to the vibrant, extraterrestrial green of peridot and the recently celebrated, durable brilliance of spinel, each stone has a unique story. Their histories are intertwined with human culture, from ancient Roman seals to modern jewelry collections, and their geological origins span from deep within the Earth to the depths of space. Understanding their properties, lore, and care requirements allows enthusiasts and collectors to appreciate these gems not only for their beauty but also for their enduring significance. Whether chosen for its color, durability, or symbolic meaning, the August birthstone trio provides a rich and rewarding field for exploration.