For individuals born in August, the choice of a birthstone is not limited to a single gem. The modern birthstone chart, widely adopted in the United States, lists peridot and spinel for the month. However, sardonyx also appears on some traditional lists, creating a trio of distinct gemstones. Each of these stones offers unique geological origins, a spectrum of colors, and varying degrees of durability, providing August-born individuals with a rich palette of options for personal jewelry. This article explores the gemological properties, historical significance, and practical considerations for peridot, spinel, and sardonyx, drawing exclusively from authoritative gemological sources to provide a comprehensive guide for enthusiasts, collectors, and jewelry buyers.
History and Lore: The Journey to August
The association of specific gemstones with calendar months is a relatively modern convention, evolving from ancient traditions. Historical texts, such as The Curious Lore of Precious Stones by George Frederick Kunz (1913), document how stones were linked to zodiac signs and later to calendar months. The modern standardization began with the National Association of Jewelers (now Jewelers of America), which established an official birthstone chart in the United States. This chart has undergone several revisions over the years, reflecting changes in availability, cultural trends, and market dynamics.
The most significant update for August came in 2016 when the American Gem Trade Association added spinel as an additional birthstone for the month. This addition was driven by spinel's historical significance and its availability in a wide range of colors, offering more options beyond the traditional peridot. The inclusion of spinel provided August-born individuals with a durable gemstone available in colors ranging from vivid reds to deep blues, challenging the perception that August was limited to a single, green hue.
Sardonyx, while not part of the modern standard chart, maintains a presence on some traditional lists and in historical references. As a banded variety of chalcedony, sardonyx has been prized for millennia for use in cameos and intaglios, with its use in such art forms dating back at least two thousand years. Its inclusion in certain birthstone lists underscores the deep historical roots of gemstone lore, where materials were valued for their symbolic meanings and aesthetic appeal long before formal standardization.
Geological Formation and Sources
The three August birthstones originate from vastly different geological environments, resulting in distinct physical and chemical properties.
Peridot is the gem-quality variety of the mineral olivine. It forms deep within the Earth's mantle and is brought to the surface by volcanic activity. Unlike many gemstones, peridot is found in a single color family—olive green to lime green—due to its iron content. Significant sources include Arizona (USA), Pakistan, Myanmar, and the island of Zabargad in the Red Sea. Its formation in mafic and ultramafic rocks makes it a gemstone intrinsically linked to the planet's geological processes.
Spinel is magnesium aluminum oxide (MgAl₂O₄) and forms in metamorphic rocks, particularly in marble, and in alluvial deposits. It is known for its exceptional durability and occurs in a spectacular array of colors, including red, blue, pink, and purple. Historically, many large red spinels were mistaken for rubies (e.g., the Black Prince's Ruby and the Timur Ruby). Major sources include Myanmar (Burma), Sri Lanka, Tajikistan, and Vietnam. The variety of colors and the gem's durability have made it a prized material for centuries.
Sardonyx is a banded variety of chalcedony, which is a microcrystalline form of quartz (SiO₂). It is characterized by straight, parallel bands of white, black, orange, red, or brown chalcedony. Sardonyx forms in volcanic and sedimentary environments where silica-rich fluids deposit layers in rock cavities. It is often cut into cabochons or carved into cameos. Sources are not detailed in the provided materials, but as a form of chalcedony, it is found in many regions where quartz is abundant.
Gemological Properties
The durability and suitability of a gemstone for jewelry are primarily determined by its hardness, toughness, and cleavage. The following table summarizes key properties for the three August birthstones, based on data from gemological references.
| Gemstone | Chemical Composition | Mohs Hardness | Key Durability Notes | Primary Color(s) |
|---|---|---|---|---|
| Peridot | (Mg, Fe)₂SiO₄ | 6.5–7 | Fair durability; prone to breakage. Suitable for rings with protective settings. | Olive to lime green |
| Spinel | MgAl₂O₄ | 8 | Excellent durability; very hard and tough. Suitable for all jewelry types, including rings. | Wide range: red, blue, pink, purple, etc. |
| Sardonyx | SiO₂ (microcrystalline quartz) | 7 | Good durability; can be scratched. Best for protected settings or items like cameos. | Banded white, black, orange, red, brown |
Peridot has a Mohs hardness of 6.5 to 7, which is reasonably tough but not as durable as harder gems. It is prone to breakage due to its crystal structure. For this reason, peridot is recommended for jewelry with protective settings, such as bezels, and should be worn with care to avoid impacts.
Spinel is one of the most durable gemstones, with a Mohs hardness of 8. It is extremely hard and tough, making it suitable for any type of jewelry, including rings and bracelets that undergo daily wear. Its durability is comparable to that of ruby and sapphire, placing it in the "excellent" category for birthstone durability.
Sardonyx, as a variety of chalcedony (quartz), has a Mohs hardness of 7. This places it in the "good" category for durability. While it is hard enough for most jewelry, it can be scratched by materials with a higher hardness. Its banded structure also makes it suitable for carving into cameos, a traditional use that leverages its layered appearance.
Symbolism and Metaphysical Beliefs
Gemstones have long been associated with symbolic meanings and metaphysical properties. These beliefs, while not scientifically proven, are an important part of cultural history and personal significance for many wearers.
Peridot is traditionally associated with strength, good fortune, and peace. Its vibrant green color is often linked to renewal and growth. In some historical beliefs, peridot was thought to ward off evil spirits and bring protection to the wearer.
Spinel has historically been associated with vitality and endurance. Its durability mirrors this symbolism, suggesting a stone that can withstand challenges. The variety of colors allows for different symbolic interpretations, with red spinel linked to passion and blue spinel to calm and wisdom.
Sardonyx has been valued for its protective qualities. In ancient times, it was believed to ward off negativity and bring stability. Its use in cameos and amulets further underscores its role as a talismanic stone, often engraved with images or symbols for specific purposes.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of gemstone jewelry. The appropriate methods depend on the gem's physical properties.
Peridot requires careful handling due to its relative fragility. It should be cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, as the heat and vibrations can cause fractures. Store peridot jewelry separately to prevent scratching by harder gems.
Spinel is highly durable and can withstand most cleaning methods. It is safe to use warm, soapy water, ultrasonic cleaners, and steam cleaners. Its hardness means it is less likely to scratch, but it should still be stored separately from other jewelry to maintain its polish.
Sardonyx, as a form of quartz, is durable but can be scratched. Cleaning with warm, soapy water and a soft cloth is recommended. Ultrasonic cleaners are generally safe, but steam cleaning should be avoided if the stone has any fractures or inclusions. Due to its use in cameos, intricate pieces should be cleaned gently to avoid damaging delicate carvings.
Conclusion
The birthstones for August—peridot, spinel, and sardonyx—offer a diverse array of choices for those born in this month. From the single green hue of peridot to the rainbow of colors in spinel and the banded patterns of sardonyx, each gemstone possesses unique geological origins, historical significance, and practical qualities. Spinel stands out for its exceptional durability and color range, making it a versatile and modern choice. Peridot, with its ancient volcanic origins, provides a classic green option, while sardonyx connects wearers to millennia of carved art and talismanic tradition. Understanding the properties and care requirements of these stones allows individuals to select jewelry that not only reflects personal style but also honors the rich legacy of these August birthstones.