Peridot, a vibrant olive-green gemstone, holds a unique position in both geological history and human culture. Designated as the modern birthstone for August, its distinct color and storied past make it a subject of fascination for gemologists, historians, and jewelry enthusiasts alike. This article explores peridot's journey from the depths of the Earth to its celebrated status as a birthstone, detailing its formation, gemological properties, historical lore, and practical care. By drawing exclusively on authoritative sources, we present a comprehensive overview of this remarkable gem.
History and Lore: From Ancient Egypt to Modern August
Peridot's history is as rich and luminous as its hue. The gem has been cherished for millennia, with its earliest documented use tracing back to ancient Egypt. Archaeological evidence suggests that peridot was mined on the Red Sea island of Zabargad (also known as St. John's Island) as early as the 15th century BCE. The Egyptians referred to peridot as the "gem of the sun," believing it possessed protective qualities against evil spirits and nightmares. This belief was so strong that peridot was often set in gold and worn as an amulet. Historical records indicate that peridot adorned the vestments of high priests and was incorporated into the treasury of the Pharaohs.
The gem's journey beyond Egypt expanded its lore. By the time of the Roman Empire, peridot was known as "topaz," though it was distinct from the topaz we recognize today. Roman historian Pliny the Elder described a green gemstone mined on an island in the Red Sea, which aligns with the characteristics of peridot. During the Middle Ages, peridot was brought to Europe by Crusaders, where it was often used in church ornamentation. Notably, the "Pala of St. Hedwig," a historic artifact housed in the Aachen Cathedral, features peridot stones.
The modern era saw peridot's official recognition as a birthstone. In 1912, the National Association of Jewellers (now the Jewellers of America) established a standardized list of birthstones. Peridot was assigned to August, alongside sardonyx. This designation was reaffirmed in the 1952 revision by the American Gem Trade Association (AGTA) and remains in place today. While some alternative lists include sardonyx or spinel for August, peridot is the most widely accepted and celebrated gem for the month. Its association with the sun aligns with August's summer season in the Northern Hemisphere, making it a fitting symbol of warmth and vitality.
Geological Formation and Sources
Peridot is unique among gemstones as it is formed deep within the Earth's mantle, unlike most gems that crystallize in the crust. It is a variety of the mineral olivine, with the chemical formula (Mg, Fe)₂SiO₄. The gem's formation requires specific conditions of high temperature and pressure, typically occurring in the Earth's mantle and brought to the surface through tectonic activity or volcanic eruptions. This origin makes peridot one of the few gems that can be found in meteorites, known as "pallasite" olivine, though such material is rarely gem-quality.
Commercial peridot mining occurs in several key locations worldwide. The most historically significant source is the island of Zabargad in the Red Sea, which remains a source of high-quality peridot, though production is limited. In the United States, peridot is notably mined in the San Carlos Apache Reservation in Arizona, a source that produces some of the finest peridot crystals, often in large sizes. Other significant sources include Pakistan, Myanmar (Burma), China, and Vietnam. Australian peridot is also documented, though it is less common in the gem trade.
The gem's color can vary from yellowish-green to olive green, depending on the iron content. Higher iron concentrations result in a deeper, more saturated green. Peridot from Arizona is often prized for its vibrant lime-green hue, while stones from Pakistan and Myanmar may exhibit a more golden or olive tone. The gem is typically found in volcanic rocks like basalt and in mantle-derived xenoliths. Unlike many gems, peridot is not treated for color enhancement, making its natural hue a direct reflection of its geological origin.
Gemological Properties
Peridot's gemological characteristics are well-documented and distinguish it from other green gemstones. Its most notable property is its color, which is caused by iron impurities in its crystal structure. The gem is pleochroic, meaning it can show slightly different shades of green when viewed from different crystal directions. However, this effect is usually subtle and not a major factor in its appearance.
The following table summarizes peridot's key gemological properties, based on data from authoritative gemological laboratories:
| Property | Description |
|---|---|
| Mineral Family | Olivine |
| Chemical Formula | (Mg, Fe)₂SiO₄ |
| Crystal System | Orthorhombic |
| Hardness (Mohs Scale) | 6.5 to 7 |
| Specific Gravity | 3.34 to 3.51 |
| Refractive Index | 1.654 to 1.690 |
| Birefringence | 0.036 |
| Optic Character | Biaxial (+) |
| Inclusions | Typical inclusions include "lily pad" inclusions (three-phase inclusions containing a solid crystal, a liquid, and a gas bubble), needle-like inclusions, and small crystals. |
Peridot has a hardness of 6.5 to 7 on the Mohs scale, making it moderately durable but suitable for jewelry that is not subjected to heavy impact, such as earrings or pendants. It is more susceptible to scratching than harder gems like sapphire (Mohs 9) or diamond (Mohs 10). The gem has no cleavage, but it has poor toughness due to its crystal structure, making it prone to chipping if struck sharply.
In terms of clarity, peridot is often found with visible inclusions. High-quality peridot is relatively clean, but the presence of "lily pad" inclusions is common and can be a diagnostic feature. The gem's refractive index and birefringence are similar to those of emerald, but peridot's lack of treatment and different inclusions help gemologists distinguish it. Color zoning is also possible, but well-cut peridot can minimize its visibility.
The gem is cut into a variety of shapes, with oval, cushion, and round cuts being popular to maximize color and brilliance. Large peridot crystals are sometimes cut en cabochon to showcase their unique inclusions or to create decorative items. The gem's transparency allows for faceted cuts that enhance its sparkle, though its refractive index is lower than that of diamond or sapphire, resulting in a more subdued brilliance.
Symbolism and Metaphysical Beliefs
Peridot's symbolism is deeply rooted in its historical associations with light, protection, and healing. In ancient Egypt, it was believed to be a "stone of the sun," warding off darkness and evil. This association with the sun continues in modern metaphysical beliefs, where peridot is thought to bring joy, abundance, and good health. It is often called the "evening emerald" due to its ability to glow under candlelight, a property that ancient civilizations found mystical.
In contemporary crystal healing, peridot is associated with the heart chakra, believed to promote emotional balance and release negative patterns. It is also linked to prosperity and success, making it a popular stone for entrepreneurs and those seeking career advancement. Some believe peridot can alleviate stress, anxiety, and physical ailments related to the heart, lungs, and digestive system. While these beliefs are not scientifically proven, they contribute to the gem's enduring appeal.
Peridot is also the traditional anniversary gemstone for the 16th year of marriage, symbolizing growth and renewal. Its green color is universally associated with nature, vitality, and rebirth, aligning with its formation in the Earth's mantle and its journey to the surface. These symbolic meanings enhance its value as a birthstone, offering a personal connection for those born in August.
Care and Cleaning
Proper care is essential to maintain peridot's beauty and longevity. Given its hardness of 6.5 to 7 and poor toughness, peridot should be protected from hard blows, abrasive surfaces, and extreme temperature changes. It is not recommended for everyday rings, especially for those with active lifestyles, but is excellent for earrings, pendants, and bracelets.
Cleaning peridot is straightforward but requires gentle methods. Use warm, soapy water and a soft brush to remove dirt and oils. Avoid harsh chemicals, such as bleach or ammonia, which can damage the gem's surface. Ultrasonic cleaners are generally safe for peridot, but steam cleaning should be avoided, as sudden temperature changes can cause fractures. Always remove peridot jewelry before engaging in activities that could expose it to impact or chemicals.
For storage, keep peridot pieces separate from harder gemstones to prevent scratching. A soft cloth pouch or a lined jewelry box is ideal. Regular inspections by a professional jeweler can help identify any potential issues, such as loose settings or surface scratches, ensuring the gem remains in optimal condition.
Conclusion
Peridot stands as a testament to the Earth's geological wonders and human cultural heritage. As the modern birthstone for August, it embodies the warmth and vitality of summer, with its vibrant green hue capturing the essence of sunlight and growth. From its ancient origins in Egyptian mines to its current status in gemology and jewelry, peridot continues to inspire and captivate. Its unique formation, distinct gemological properties, and rich symbolism make it a gemstone of both scientific interest and personal significance. By understanding its history, properties, and care requirements, enthusiasts can fully appreciate peridot's enduring beauty and value.