The month of August, situated in the heart of summer, is uniquely represented by three distinct gemstones: peridot, spinel, and sardonyx. This trio offers a remarkable spectrum of color, history, and geological origin, reflecting the vibrant and diverse character of the season. Peridot, the traditional and most widely recognized August birthstone, is a gem formed under extreme conditions, found both deep within the Earth and in meteorites from outer space. Spinel, a gem long mistaken for ruby, has recently gained acclaim for its own dazzling beauty and durability. Sardonyx, the original August birthstone, boasts a history stretching back over four millennia, valued for its distinctive banding and symbolic significance. Together, these stones provide August-born individuals with a rich palette of choices, each with its own unique story and properties. This article will delve into the history, geology, gemological characteristics, and cultural lore of these three captivating gems, providing a comprehensive guide for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore of August's Birthstones
The history of August's birthstones is a tapestry woven from ancient trade, geological discovery, and evolving cultural preferences. Sardonyx stands as the most ancient of the trio, with a documented history that dates back more than 4,000 years. As the original August birthstone, it was highly prized in ancient civilizations for its use in cameos and intaglios, where its contrasting layers of brownish-red sard and white onyx allowed for intricate and elegant carvings. Its significance extended beyond mere adornment; sardonyx was believed to confer strength, courage, and eloquence upon its wearer, making it a popular choice for seals and amulets.
Peridot’s historical narrative is equally compelling and often intertwined with other famous gemstones. The oldest recorded source of peridot is the Egyptian island of Zabargad, also known as St. John’s Island in the Red Sea. This island, however, had a fearsome reputation, nicknamed the "Island of Death" due to the perilous conditions of its ancient mines. Despite the dangers, peridot was highly valued by the ancient Egyptians, who associated the gem with light and the sun. The word "peridot" itself is believed to derive from the Arabic faridat, meaning gem. Throughout history, peridot has often been confused with other gems. The Red Sea island of Topazios, a source of the name "topaz," actually produced peridot. Furthermore, the 200-carat gems adorning the Shrine of the Three Holy Kings in Germany’s Cologne Cathedral, long believed to be emeralds, are in fact peridot. Some historians even speculate that Cleopatra’s famed emerald collection may have been composed of peridot.
Spinel’s history is one of mistaken identity and recent reassessment. For centuries, large red spinels were confused with rubies, earning names like the "Black Prince's Ruby" in the British Imperial State Crown, which is actually a red spinel. This confusion led to spinel being underappreciated for much of its history. It was only in the late 18th and early 19th centuries that spinel was recognized as a distinct mineral species. Its official addition to the list of August birthstones in 2016 by the American Gem Trade Association (AGTA) solidified its modern status, offering a durable and vibrant alternative to ruby for those born in the eighth month.
The selection of three birthstones for August is a result of historical tradition, gemstone availability, and the evolving preferences of the jewelry industry. While sardonyx holds ancient roots, peridot emerged as the most popular traditional choice, and spinel was added more recently to provide greater variety and address market demand for a durable, colorful gem.
Geological Formation and Sources
The origins of these three gemstones are as diverse as their appearances, spanning terrestrial and extraterrestrial environments.
Peridot is the gem variety of the mineral olivine, with the chemical formula (Mg, Fe)₂SiO₄. Its formation is notably extreme. It is commonly found in the hardened lava that carries it from deep within Earth’s mantle, a process that brings the gem to the surface. This source makes peridot one of the few gems found in igneous rock. Perhaps more uniquely, peridot is also found in meteorites that have traveled from outer space to Earth. A notable terrestrial source is a beach in Hawaii named Peridot Beach, where the sand gleams green with tiny pieces of the gemstone, likely the result of a meteor crashing into the ocean and the waves slowly breaking it down. Historically, the Egyptian island of Zabargad was a primary source. Today, most commercial peridot originates from China, Myanmar (Burma), and Vietnam. Other sources include Afghanistan, Pakistan, and the United States (Arizona, New Mexico, and Hawaii).
Spinel is a magnesium aluminum oxide (MgAl₂O₄) and forms in the metamorphic rock of marble and alluvial deposits. It is often found alongside ruby in the gem-bearing gravels of places like Myanmar (Burma), Sri Lanka, and Thailand. The finest spinel crystals, particularly the vibrant red and pink varieties, have historically come from the Mogok region of Myanmar. Other significant sources include Vietnam, which produces fine red and pink spinels, as well as Afghanistan, which is known for its blue spinels. Spinels from Tanzania can exhibit a range of colors, including the rare cobalt-blue variety.
Sardonyx is a variety of onyx, which itself is a banded form of chalcedony, a cryptocrystalline form of silica (SiO₂). It is characterized by alternating layers of reddish-brown sard and white or black onyx. This banding is a result of successive layers of silica deposited in cavities within host rock, often in volcanic or sedimentary environments. While sardonyx can be found in various locations worldwide, including India, Brazil, Germany, and the United States, the finest quality material for carving is historically associated with India.
Gemological Properties
Understanding the physical and optical properties of these gems is essential for identification, valuation, and care. The following table summarizes key gemological data for peridot, spinel, and sardonyx.
| Property | Peridot | Spinel | Sardonyx |
|---|---|---|---|
| Mineral Species | Olivine | Spinel | Chalcedony (Quartz) |
| Chemical Formula | (Mg, Fe)₂SiO₄ | MgAl₂O₄ | SiO₂ |
| Crystal System | Orthorhombic | Cubic | Trigonal (macrocrystalline quartz) |
| Mohs Hardness | 6.5 - 7 | 8 | 7 |
| Refractive Index | 1.65 - 1.69 | 1.71 - 1.73 | 1.53 - 1.54 |
| Specific Gravity | 3.34 | 3.58 - 3.61 | 2.58 - 2.64 |
| Common Colors | Yellowish-green to greenish-yellow | Wide range: red, pink, orange, purple, blue, black | Alternating bands of brownish-red (sard) and white/gray (onyx) |
| Transparency | Transparent to translucent | Transparent to translucent | Translucent to opaque |
| Durability | Good, but can be brittle due to cleavage | Excellent, no cleavage, good toughness | Fair to good, resistant to chipping but can be brittle |
Peridot is a relatively durable gem with a hardness of 6.5 to 7 on the Mohs scale. Its most prized color is a rich, olive green, free of brownish tints. The gem's color is caused by trace amounts of iron within its crystal structure. Peridot is pleochroic, meaning it can show slightly different shades of green when viewed from different crystal directions. While generally clean, peridot can have inclusions that resemble lily pads or tiny needles.
Spinel is an exceptionally durable gem, with a hardness of 8 on the Mohs scale and no cleavage, making it an excellent choice for all types of jewelry. It exhibits a brilliant vitreous luster and can display a range of colors, from the classic vibrant red (often mistaken for ruby) to pinks, oranges, purples, and the rare cobalt blue. Its refractive index is higher than that of ruby, contributing to its excellent brilliance. Red spinel's color is caused by trace amounts of chromium, similar to ruby, while other colors are due to iron and other elements.
Sardonyx, as a variety of chalcedony, has a hardness of 7 on the Mohs scale. Its defining characteristic is its banding, which results from the parallel growth of different colored layers of silica. The reddish-brown layers are colored by iron oxides, while the white layers are pure silica. Sardonyx is often carved into cameos, intaglios, and beads. Its refractive index is lower than that of peridot or spinel, and it is typically translucent rather than transparent.
Symbolism and Metaphysical Beliefs
Across cultures and centuries, these gemstones have been imbued with a wide array of symbolic meanings and metaphysical properties.
Peridot has been historically associated with light and the sun. Ancient Egyptians believed it could ward off evil and protect against nightmares. It was also thought to promote openness, honesty, and emotional balance. In modern crystal healing, peridot is often linked to the heart chakra, believed to foster love, compassion, and forgiveness. Its green color is universally associated with growth, renewal, and prosperity.
Spinel, while often living in the shadow of ruby, has accumulated its own lore. Red spinel, due to its long confusion with ruby, inherited many of ruby’s symbolic attributes, such as representing vitality, passion, and courage. It is also believed to revitalize the body and mind, providing a sense of rejuvenation and energy. The gem is sometimes associated with the root and heart chakras, promoting physical and emotional stability.
Sardonyx has a long history of symbolism tied to strength, protection, and communication. In ancient Rome, it was worn by soldiers and orators to gain courage and eloquence. It was also believed to be a stone of happiness and good fortune, often used in talismans and amulets. In some belief systems, sardonyx is thought to enhance self-control and discipline, helping the wearer to overcome challenges and achieve their goals.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, and their specific properties dictate the best practices for cleaning and storage.
Peridot, with a hardness of 6.5 to 7, is relatively durable but can be prone to scratching if not handled carefully. It is also somewhat brittle and can cleave if struck with force. To clean peridot, use warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, as sudden temperature changes can cause damage. It is also advisable to avoid harsh chemicals and prolonged exposure to strong sunlight, which can cause fading in some specimens.
Spinel is one of the most durable gems, making it very easy to care for. Its hardness of 8 and lack of cleavage make it resistant to scratching and breaking. Spinel can be safely cleaned with warm, soapy water and a soft brush. It is also generally safe for ultrasonic cleaners and steam cleaning, though caution is always recommended for any gemstone with inclusions. Its durability makes it an excellent choice for everyday jewelry.
Sardonyx, as a form of chalcedony, is relatively hard but can be brittle. It is important to avoid knocks and impacts that could chip or crack the stone. Cleaning sardonyx is straightforward: use warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, as the vibrations and heat can potentially damage the stone, especially if it has any existing fractures. Store sardonyx jewelry separately to prevent scratching by harder gems.
Conclusion
The birthstones of August—peridot, spinel, and sardonyx—offer a compelling study in diversity, from their geological origins to their cultural significance. Peridot, with its celestial and terrestrial formation, presents a gem of luminous green light. Spinel, once mistaken for ruby, now stands proudly on its own merits as a brilliantly durable and colorful gem. Sardonyx, the ancient original, provides a timeless connection to the carvers and warriors of antiquity. Together, they form a trio that celebrates the richness of summer. For those born in August, this selection provides not just a range of beautiful colors and styles, but also a deep well of history, science, and symbolism from which to choose a personal and meaningful gemstone.