August is a month of transition, bridging the warmth of summer with the approach of autumn. For those born in this vibrant month, the choice of a birthstone is uniquely rich, with three distinct gemstones officially recognized: the radiant peridot, the underappreciated spinel, and the ancient sardonyx. Each carries its own history, geological story, and symbolic weight, offering a diverse palette of color and meaning. This article delves into the gemological properties, historical significance, and cultural lore of these three August birthstones, providing a comprehensive guide for enthusiasts, collectors, and anyone captivated by the world of gemstones.
The modern standardization of birthstones is a relatively recent development, but its roots stretch back millennia. The concept is traditionally linked to the twelve gemstones adorning the breastplate of Aaron in the Old Testament and the foundation stones of the New Jerusalem in the Book of Revelation. Over centuries, these stones became associated with zodiac signs and, eventually, calendar months. In the United States, the National Association of Jewelers (now Jewelers of America) established the first official birthstone chart, which has been revised over time to include new discoveries and market preferences. For August, the modern list includes peridot and spinel, while sardonyx holds its place as the traditional stone. This evolution reflects a growing desire for variety, allowing individuals to select a gem that resonates with their personality or aesthetic.
The Historical Journey of August's Gems
The history of August's birthstones is a tapestry of ancient confusion, rediscovery, and enduring symbolism. Among the three, sardonyx is the original and most historically venerable. As a variety of onyx, sardonyx is characterized by its layers of reddish-brown sard and black or white onyx, creating a striking banded appearance. Its use dates back over 4,000 years, with significant presence in ancient Roman and Greek cultures. Sardonyx was a favored material for signet rings and cameos, prized for its ability to be carved into intricate scenes and figures. The Romans believed it could protect its wearer during battles and attract favor from the gods. Its historical importance is underscored by its inclusion in the original list of birthstones, representing August for centuries before the addition of other gems.
Peridot, the brilliant yellowish-green gem, has a history steeped in mistaken identity and celestial wonder. This gem is the gem variety of the mineral olivine, a common rock-forming mineral found in Earth's mantle. Peridot's history is often intertwined with topaz and emerald. For instance, the Red Sea island of Topazios, a purported source of the name "topaz," was actually a source of peridot. Many ancient and medieval gems believed to be emeralds have been identified as peridot, including the 200-carat stones in the Shrine of the Three Holy Kings in Germany’s Cologne Cathedral. Some historians even speculate that Cleopatra’s famed emerald collection may have been composed of peridot. The name "peridot" itself derives from the Arabic faridat, meaning "gem." This August birthstone was valued in many ancient cultures and is notably one of the few gems found in meteorites, adding to its mystique as a stone from the heavens.
Spinel has a more recent historical narrative, defined largely by its centuries-long confusion with ruby. For much of history, large red spinels were mistaken for rubies and held in equal esteem. The most famous example is the "Black Prince's Ruby," a 170-carat red spinel that is part of the British Imperial State Crown. Similarly, the "Timur Ruby," a 361-carat red spinel, was also misidentified for centuries. It was not until the development of modern gemology that spinel was recognized as a distinct mineral species. This underappreciation has only recently been rectified, as today's consumers seek vibrant alternatives to ruby. While spinel was added as an official August birthstone in a more recent update to the birthstone chart, its history as a "ruby imposter" gives it a unique and compelling backstory.
Geological Formation and Global Sources
The geological origins of these three gemstones could not be more different, reflecting the diverse processes that create beauty within the Earth and beyond.
Peridot is uniquely formed under extreme conditions. It is primarily found in the Earth's upper mantle and is brought to the surface through volcanic activity. The gem crystals are often carried within hardened lava, which can then be mined from volcanic regions. Significant sources include the San Carlos Apache Reservation in Arizona, which is a major global producer of peridot. Furthermore, peridot is one of the few gems found in meteorites, specifically pallasite meteorites, which contain crystals of olivine. This extraterrestrial origin is a rare and fascinating aspect of the gemstone, linking it directly to the cosmos.
Spinel forms under high-temperature and low-pressure metamorphic conditions, often in the same geological environments as ruby and sapphire. It is commonly found in alluvial deposits, where water has eroded and transported the crystals from their original host rock. Major sources of spinel include Myanmar (Burma), Sri Lanka, and Vietnam. The Burmese region, in particular, has produced some of the world's finest red and pink spinels. Unlike peridot, spinel's formation is entirely terrestrial, though its deep red varieties have long been associated with the fiery depths of the Earth.
Sardonyx is a variety of the mineral chalcedony, which is a microcrystalline form of quartz. Its formation involves the deposition of silica in alternating layers, creating the characteristic bands of color. Sardonyx is typically found in regions with volcanic activity or in sedimentary deposits. Historically, significant sources were located in India, particularly around the city of Puna. Today, sardonyx is also sourced from Brazil, Germany, and the United States. Its formation is a slower, more gradual process compared to the volcanic genesis of peridot, reflecting the patient artistry of geological time.
Gemological Properties: A Scientific Profile
Understanding the physical and chemical properties of these gemstones is essential for their identification, valuation, and care. The following table summarizes key gemological data for peridot, spinel, and sardonyx, based on standard references.
| Property | Peridot | Spinel | Sardonyx |
|---|---|---|---|
| Chemical Formula | (Mg,Fe)₂SiO₄ | MgAl₂O₄ | SiO₂ (microcrystalline quartz) |
| Crystal System | Orthorhombic | Cubic | Trigonal (macrocrystalline) / Hexagonal (microcrystalline) |
| Hardness (Mohs) | 6.5 – 7 | 8 | 6.5 – 7 |
| Refractive Index | 1.654 – 1.690 | 1.718 | 1.530 – 1.540 |
| Specific Gravity | 3.34 | 3.60 | 2.65 |
| Key Colors | Yellowish-green to greenish-yellow | Wide range: red, pink, blue, purple, black, white | Bands of brown (sard) and black/white (onyx) |
| Durability | Fairly durable, but can be brittle due to cleavage | Excellent durability, no cleavage | Fairly durable, but susceptible to scratches and acid damage |
Peridot is a relatively hard gem but can be brittle due to its cleavage properties, meaning it can break along certain planes if struck with force. Its distinctive green color comes from traces of iron within its chemical structure. The most prized peridot exhibits a pure, vibrant green with minimal brownish tints.
Spinel boasts excellent durability with a hardness of 8 on the Mohs scale and no cleavage, making it suitable for all types of jewelry, including rings and bracelets. Its chemical composition (MgAl₂O₄) allows for a remarkable range of colors, with red and pink being the most valuable, often commanding prices comparable to fine rubies and sapphires.
Sardonyx, as a variety of chalcedony, is less hard than spinel and peridot but is still suitable for carving and intaglios. Its hardness of 6.5-7 is adequate for many jewelry settings, but it requires care to avoid scratches and chemical exposure. The banding is its defining characteristic, and skilled artisans select pieces with sharp, contrasting layers for the most striking cameos and signets.
Symbolism, Lore, and Metaphysical Beliefs
Beyond their physical beauty, these gemstones are imbued with layers of symbolism and metaphysical beliefs that have evolved over time.
Peridot has long been associated with the sun. In ancient Egypt, it was called the "gem of the sun" and was believed to protect its wearer from the "terrors of the night." It was also thought to promote openness, honesty, and clarity of thought. In modern crystal healing, peridot is often linked to the heart chakra, believed to attract love and alleviate stress. Its green color naturally connects it to themes of growth, renewal, and prosperity.
Spinel, particularly the red varieties, has historically shared the symbolism of ruby—passion, vitality, and protection. Because it was mistaken for ruby for so long, it inherited many of ruby's legendary properties. In some traditions, spinel is believed to revitalize the body and mind, promoting physical and mental energy. Its wide color range also lends it to different meanings; for example, blue spinel may be associated with calm and communication, while pink spinel is linked to love and compassion.
Sardonyx carries a rich legacy of protective symbolism. In ancient Rome, it was a talisman for warriors, believed to grant strength and protect in battle. It was also associated with eloquence and persuasion, making it a popular choice for orators and leaders. As a stone of the foundation, sardonyx is thought to provide stability, courage, and happiness. In some belief systems, it is used to ground the wearer and foster a sense of security.
It is important to note that while these metaphysical beliefs are part of the cultural history of these gemstones, they are not supported by scientific evidence and should be viewed as traditional lore rather than gemological fact.
Care and Cleaning: Preserving Your Gemstone
Proper care is essential to maintain the beauty and longevity of any gemstone. The physical properties of peridot, spinel, and sardonyx dictate specific maintenance routines.
Peridot requires gentle care. With a hardness of 6.5-7, it can be scratched by harder materials. It is also sensitive to rapid temperature changes and harsh chemicals. Cleaning should be done with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, as these can cause damage due to its cleavage.
Spinel is one of the most durable and low-maintenance gemstones. Its hardness of 8 and lack of cleavage make it resistant to scratches and breakage. It can be safely cleaned with warm, soapy water, a soft brush, and even in an ultrasonic cleaner (except for stones with fractures or inclusions). Steam cleaning is generally acceptable but should be approached with caution for very large or heavily included stones.
Sardonyx, being a form of chalcedony, is relatively durable but can be susceptible to scratching and damage from acids and high heat. It is best cleaned with a soft cloth and mild soapy water. Avoid ultrasonic cleaners, as the vibrations can potentially loosen any fillers used in lower-quality stones or affect the stability of the banding. As with all gemstones, it is advisable to store sardonyx pieces separately to prevent scratching.
Conclusion
The August birthstones—peridot, spinel, and sardonyx—offer a fascinating study in contrast and history. From the solar brilliance of peridot, born of the Earth's mantle and the cosmos, to the fiery passion of spinel, long mistaken for ruby, and the ancient, protective bands of sardonyx, each gemstone provides a unique narrative. Their geological origins span from volcanic eruptions to metamorphic processes and slow sedimentary deposition. Their colors range from vibrant green to a spectrum of reds, pinks, and banded earth tones. Their histories are intertwined with ancient empires, medieval crowns, and modern gemological discoveries. For those born in August, the choice of a birthstone is not merely a matter of color preference but an opportunity to connect with a rich tapestry of science, history, and symbolism. Whether drawn to the celestial origins of peridot, the rediscovered glory of spinel, or the timeless artistry of sardonyx, there is a gemstone perfectly suited to celebrate the unique spirit of the August-born.