Peridot, the gemstone designated for the month of August, stands as a singular and luminous presence in the world of colored gems. Unlike many other birthstones, which are forms of a mineral species, peridot is the gemological name for the gem variety of the mineral olivine, specifically the magnesium-rich forsterite end-member. Its distinctive olive to lime green color, a result of its iron content, is instantly recognizable and has captivated humanity for millennia. While often associated with the sun due to its warm hues, its designation as a birthstone is firmly rooted in modern standardization, yet its history stretches back to ancient civilizations. This article delves into the multifaceted nature of peridot, exploring its geological origins, its journey through history and lore, its defining gemological properties, and its practical care, all synthesized from authoritative sources to provide a definitive guide for enthusiasts and collectors alike.
History and Lore: From Ancient Talismans to Modern Standardization
The story of peridot is one of ancient reverence and modern rediscovery. Historical records indicate that peridot has been mined and valued for over three and a half millennia. One of the earliest known sources was the island of Zabargad (St. John’s Island) in the Red Sea, which was exploited for peridot from around 1500 B.C. until the 19th century. The gemstone was particularly prized in Ancient Egypt, where it was known as the "gem of the sun." Pliny the Elder, the Roman naturalist, described peridot as possessing a "greenish-yellow" color and noted its use in jewelry. The gems from Zabargad were often of a large size, and many of the peridots found in the world’s treasuries, including those in the Topkapi Palace in Istanbul and the Hofburg Palace in Vienna, are believed to have originated from this ancient source.
The association of peridot with the month of August, however, is a product of the 20th century. The modern birthstone list was standardized in 1912 by the National Association of Jewelers (now Jewelers of America). This list was created to reduce confusion and establish a consistent reference for jewelers and consumers. Peridot was assigned to August, providing a unique green gemstone for that summer month. This decision was not arbitrary; it followed a tradition of linking specific stones to calendar months, a concept that itself evolved from much older beliefs. Earlier traditions, such as those described by scholars like St. Jerome in the 5th century, connected the twelve stones of the High Priest’s breastplate to the twelve months and zodiacal signs. However, the specific practice of wearing a gemstone as a "natal stone" is believed to have originated in Poland during the 18th century.
The modern list has seen revisions since 1912 to accommodate new discoveries and changing tastes. For August, the list was expanded to include spinel as an alternative birthstone, offering a wider palette of colors beyond peridot’s green. Sardonyx, a banded variety of chalcedony, also appears on some traditional lists for August. This evolution reflects a broader trend in birthstone charts, which can vary by era, culture, and country. For instance, the traditional British chart includes bloodstone for March and rock crystal for April, while the Hindu Ayurvedic system is based on astrological signs rather than calendar months. Despite these variations, peridot’s position as the primary modern birthstone for August remains firmly established.
Geological Formation and Sources
Peridot’s formation is a direct result of its unique geological origins. As a gem variety of olivine, it crystallizes deep within the Earth’s mantle under high temperatures and pressures. Unlike many gemstones that form in pegmatites or hydrothermal veins, peridot is commonly found in igneous rocks, particularly in peridotite xenoliths brought to the surface by volcanic activity. It can also be found in certain metamorphic rocks and, most notably for gemstones, in alluvial deposits where it has been eroded from its primary source and concentrated by water or wind.
The primary sources of gem-quality peridot are geographically diverse. Historically, the Red Sea island of Zabargad was the most significant source, but its production declined in the 19th century. Today, the most important sources are located in Pakistan, Myanmar (Burma), and the United States. The Pakistani deposits, particularly in the Kohistan region, yield large, high-quality crystals with a vibrant yellow-green color. Myanmar is known for producing peridot with a rich, deep olive green hue. In the United States, peridot is found in volcanic regions, with notable deposits in Arizona (San Carlos Apache Reservation) and New Mexico. The Arizona deposits, in particular, are known for producing peridot in situ within basaltic rock, a testament to its volcanic origins.
Other sources include Australia, Brazil, China, Kenya, Mexico, and Norway, each contributing peridot with slight variations in color and quality. The gemstone’s formation in mantle xenoliths means that some peridot crystals can be remarkably large, with faceted stones over 100 carats not uncommon. This accessibility, combined with its distinct color, has made peridot a popular choice for jewelry designers seeking a gemstone that is both beautiful and relatively affordable.
Gemological Properties
Peridot possesses a set of gemological properties that make it both distinctive and durable, though it requires careful consideration in jewelry design. The following table summarizes its key characteristics:
| Property | Description |
|---|---|
| Mineral Species | Olivine (specifically, the forsterite-rich variety) |
| Chemical Formula | (Mg, Fe)₂SiO₄ |
| Crystal System | Orthorhombic |
| Color | Olive green to yellowish-green; color is primarily due to iron content. |
| Hardness (Mohs Scale) | 6.5 to 7 |
| Refractive Index | 1.65 to 1.69 |
| Specific Gravity | 3.34 to 3.45 |
| Luster | Vitreous (glass-like) |
| Transparency | Transparent to translucent |
| Cleavage | Imperfect to poor |
| Fracture | Conchoidal |
Color: The signature color of peridot ranges from light yellowish-green to a deep olive green. The intensity of the green is directly related to the iron content within the crystal structure. Unlike many other colored gemstones, peridot does not typically undergo heat treatment to alter its color, making its natural hue a key value determinant.
Hardness and Durability: With a Mohs hardness of 6.5 to 7, peridot is moderately hard, making it suitable for most types of jewelry. However, it is not as hard as quartz (7) or corundum (sapphire/ruby, 9), so it can be scratched by harder materials. Its cleavage is imperfect, meaning it can be prone to chipping or breaking if struck with sufficient force. Therefore, while it can be used in rings, it is often recommended for pendants and earrings where it is less likely to receive impact.
Clarity and Cut: Peridot often contains inclusions, such as small fluid-filled cavities ("fingerprints") or mineral inclusions. These are generally accepted as part of the stone’s character and do not typically detract from its beauty if not overly prominent. The lack of strong dichroism (showing two distinct colors when viewed from different angles) makes it relatively easy to cut, and it is commonly faceted in brilliant or step cuts to maximize its brilliance. Cabochon cuts are also used for larger stones or those with inclusions.
Optical Properties: Peridot has a refractive index of 1.65 to 1.69 and a birefringence of about 0.036. It is strongly pleochroic, though the color difference between the two directions is usually not dramatic. Under magnification, the characteristic "fingerprints" (tiny fluid inclusions) are a reliable identifier.
Symbolism and Metaphysical Beliefs
Beyond its physical properties, peridot is steeped in symbolism and metaphysical lore, much of which is derived from its historical associations and color. In ancient Egypt, it was called the "gem of the sun" and was believed to protect against evil spirits and nightmares. It was often worn as an amulet, and its connection to the sun god Ra imbued it with attributes of light, life, and vitality. The ancient Egyptians mined it extensively, and it was a favorite of Cleopatra, though many of her emeralds were likely peridot.
In medieval Europe, peridot was thought to have healing properties. It was believed to promote health, peace, and happiness, and to ward off negative emotions like jealousy and anger. Some legends held that it could help alleviate insomnia and bring restful sleep. Its association with the heart chakra in modern crystal healing practices stems from its green color, which is linked to growth, renewal, and emotional balance.
In the context of astrology, while there is no official standardized list of birthstones based on astrological signs, some traditional associations exist. Peridot is sometimes linked to the zodiac sign of Leo. This connection is not part of the official birthstone list but is found in alternative charts and metaphysical traditions. For those who resonate with their zodiac sign, exploring such associations can be a personal practice, though it is important to note that these beliefs are cultural and spiritual in nature rather than gemological.
The symbolism of peridot as a birthstone for August aligns with its vibrant, summery color. It represents warmth, abundance, and the fullness of life, making it a meaningful gift for those born in the eighth month. Its durability also symbolizes resilience and longevity, qualities often desired in personal talismans.
Care and Cleaning
Proper care is essential to maintain the beauty and integrity of peridot jewelry. Given its moderate hardness and imperfect cleavage, it requires mindful handling. The following guidelines are based on its gemological properties:
Cleaning: Peridot can be safely cleaned using warm, soapy water and a soft brush. Avoid using ultrasonic cleaners, as the vibrations can cause fractures in stones with inclusions or existing chips. Steam cleaners are also not recommended due to the potential for thermal shock. After cleaning, rinse thoroughly and dry with a soft, lint-free cloth. For routine maintenance, a simple wipe with a damp cloth is sufficient to remove oils and dust.
Storage: Store peridot jewelry separately from other gems and metals to prevent scratching. A soft pouch or a lined jewelry box is ideal. Avoid exposing peridot to sudden temperature changes, as this can cause internal stress and lead to cracking.
Wearing Precautions: While peridot is durable enough for everyday wear, it is best to remove it during activities that could subject it to hard knocks or chemicals, such as gardening, sports, or cleaning with harsh chemicals. Prolonged exposure to direct sunlight or high heat should be avoided, as it may cause fading, though this is rare for peridot.
Professional Maintenance: Periodic inspection by a professional jeweler is advisable, especially for settings like rings that may experience wear. The jeweler can check the security of the setting and the condition of the stone, ensuring it remains safe for long-term wear.
Conclusion
Peridot, the birthstone of August, is a gemstone of remarkable character and history. From its ancient origins in the Red Sea to its modern status as a standardized birthstone, it has consistently captivated with its unique olive-green hue. Its geological formation in the Earth’s mantle gives it a distinct identity, while its gemological properties—moderate hardness, vitreous luster, and characteristic inclusions—define its use in jewelry. The symbolism attached to peridot, from the ancient Egyptian "gem of the sun" to modern associations with Leo, adds layers of cultural and spiritual significance. Proper care, mindful of its physical properties, ensures that this radiant gem can be enjoyed for generations. As a testament to both nature’s artistry and human tradition, peridot remains a luminous and enduring choice for those born in August.