Peridot, a gemstone celebrated for its vibrant green hues, holds a unique position in the world of colored stones. While technically a variety of the mineral olivine, peridot is distinguished as the primary birthstone for August, a designation solidified in 1937 by the National Association of Goldsmiths, though it previously served as a September birthstone. Its history is interwoven with tales of ancient civilizations, mistaken identities with other gems, and a geological origin as diverse as volcanic eruptions and even extraterrestrial arrivals. This article will delve into the history, geological formation, gemological properties, and cultural significance of this captivating gem.
History and Lore
The story of peridot stretches back millennia. Evidence suggests its use dates back as early as the second century BCE, appearing in the jewelry of priests. Throughout medieval Europe, peridot adorned chalices and church decorations, often mistakenly identified as emeralds. This misidentification continued for centuries, with the Red Sea island of Topazios – the purported source of topaz – actually yielding significant quantities of peridot. Cleopatra herself is believed to have favored peridot, potentially mistaking it for emeralds in her famed collection.
The name “peridot” originates from the Arabic word faridat, meaning “gem.” Beyond its aesthetic appeal, peridot has long been valued as a protective talisman, believed to ward off evil spirits and “terrors of the night.” It also symbolizes a 16th wedding anniversary, representing unwavering love and admiration. The gem’s association with wealth is reflected in its ancient Greek name, peridona, meaning “to radiate wealth.”
Geological Formation and Sources
Peridot’s formation is intrinsically linked to volcanic activity. Most peridot originates from olivine-rich volcanic rocks, specifically those formed during massive volcanic eruptions. A notable source is the San Carlos Apache Indian Reservation, where lava flows created a landscape rich in peridot deposits, and where Apache families have mined the gem for decades.
However, peridot’s origins aren’t solely terrestrial. Remarkably, gem-quality peridot has also been discovered within pallasite meteorites – stony-iron meteorites composed of nickel-iron and olivine. While thousands of meteorites have impacted Earth, only a select few contain peridot of sufficient quality for use in jewelry.
Gemological Properties
Peridot is a silicate mineral belonging to the olivine group, with a general formula of (Mg,Fe)₂SiO₄, indicating a composition of magnesium, iron, and silicon. The presence of iron is responsible for peridot’s characteristic green color, with the intensity of the hue directly correlating to the amount of iron present. While most peridot exhibits a yellowish-green to greenish-yellow color, shades can also include brownish and olive tones.
Olivine encompasses a range of minerals, including forsterite (magnesium silicate), fayalite (ferrous iron silicate), and tephroite (manganese silicate). Most gem-quality peridot falls within the series between magnesium-rich forsterite and iron-rich fayalite. Tephroite, a manganese-dominant variety, is less common. All share the same crystal structure, differing primarily in their silicate composition.
Several optical properties distinguish peridot. It exhibits a relatively high birefringence (0.035 to 0.052), meaning it splits light into two rays, and a high relief, causing its grain boundaries to appear sharp and distinct under magnification. While peridot typically occurs in shades of green, rare variations like color-changing tephroite can shift from bluish-gray or grayish-green in daylight to reddish-brown under incandescent light.
The following table summarizes key gemological properties:
| Property | Value |
|---|---|
| Chemical Formula | (Mg,Fe)₂SiO₄ |
| Mineral Class | Olivine |
| Color | Yellowish-green to greenish-yellow |
| Birefringence | 0.035 - 0.052 |
| Relief | High |
Symbolism and Metaphysical Beliefs
Throughout history, peridot has been imbued with symbolic meaning. Beyond its protective qualities against negative energies, it is associated with healing and progress, believed to connect with the heart chakra (anahata) and foster emotional well-being. Some believe peridot possesses cleansing properties, facilitating a deeper connection with one’s inner self.
Care and Cleaning
Peridot, with a Mohs hardness of 6.5 to 7, is considered a relatively durable gemstone, but requires careful handling. It is susceptible to scratching from harder materials and should be protected from impacts. Cleaning peridot jewelry is best achieved with warm, soapy water and a soft brush. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone. Due to its birefringence, peridot can exhibit double vision under magnification, but this is a natural characteristic and does not indicate damage.
Olivine vs. Peridot: Understanding the Difference
The terms “olivine” and “peridot” are often used interchangeably, but it’s important to understand the distinction. “Olivine” refers to the entire mineral class, encompassing a group of silicate minerals. “Peridot” specifically denotes the gem-quality variety of olivine, prized for its vibrant green color and suitability for jewelry. While all peridot is olivine, not all olivine is peridot.
Conclusion
Peridot, the captivating August birthstone, boasts a rich history, a fascinating geological origin, and a vibrant green hue that has captivated civilizations for centuries. From its ancient roots as a prized possession of royalty to its modern-day status as a beloved gemstone, peridot continues to symbolize beauty, protection, and enduring love. Its unique formation, both on Earth and in the cosmos, adds to its mystique, making it a truly remarkable gem.