August is a unique month in the gemological calendar, distinguished by not one, but three official birthstones: peridot, spinel, and sardonyx. This trio offers a remarkable spectrum of color, history, and meaning, reflecting the vibrant energy of summer. While peridot is perhaps the most widely recognized today, the recent addition of spinel and the ancient legacy of sardonyx provide a rich tapestry of choices for those born in this month. These gems range from the deep olive greens forged in the Earth's mantle to the fiery reds and blues mistaken for rubies for centuries, and the banded earthy fortitude of ancient talismans. This article provides a detailed exploration of each of these three distinct birthstones, examining their unique geological origins, gemological properties, historical significance, and the cultural lore that has cemented their place as symbols of August.
Peridot: The Gem of the Sun and the Stars
Peridot stands out as the most famous of the August birthstones, celebrated for its distinctive and consistent lime-green glow. As the gemological variety of the mineral olivine, its color is one of its defining characteristics, ranging from yellowish-green to deep olive. This unique hue has a long history of causing confusion; for centuries, peridot was mistaken for other precious green stones, including emerald. Historical records suggest that some of Cleopatra's famed emerald collection may, in fact, have been peridot. Similarly, the 200-carat gems adorning the Shrine of the Three Holy Kings in Germany's Cologne Cathedral, long believed to be emeralds, were later identified as peridot. This confusion even extended to its mining locations, as the Red Sea island of Topazios, a source that lent its name to topaz, actually produced peridot.
The etymology of "peridot" is traced to the Arabic word faridat, meaning "gem." Its value was recognized in numerous ancient and medieval cultures, where it was not only admired for its beauty but also revered for its perceived protective and healing powers. Ancient beliefs held that peridot could ward off nightmares and bring happiness and strength to the wearer. In the Middle Ages, it was associated with foresight and inspiration, while Romans used the stone as a defense against enchantment.
The allure of peridot extends beyond earthly origins. In a testament to its extraterrestrial connections, peridot was discovered in comet dust brought back by the Stardust space probe in 2005. This discovery highlights the gem's unique formation process. Unlike many gems that crystallize in the Earth's crust, peridot is formed under extreme conditions deep within the Earth's mantle. It is brought to the surface by volcanic activity and can be found in hardened lava. Its presence in meteorites confirms that the conditions for its creation can also occur in outer space. In addition to its status as an August birthstone, peridot is also the designated gemstone for a 16th wedding anniversary.
Gemological Properties of Peridot
Peridot possesses a distinct set of physical characteristics that define its identity as a gemstone. Its chemical composition is (Mg, Fe)₂SiO₄, which places it in the olivine mineral group. The presence of iron is responsible for its characteristic green color. On the Mohs scale of hardness, peridot rates between 6.5 and 7.0, making it a moderately durable gem suitable for jewelry, though it requires more care than harder stones like sapphire or diamond. Its crystal system is orthorhombic.
The gem's refractive index typically falls between 1.65 and 1.69, and it is doubly refractive. While it lacks a distinct cleavage plane, it exhibits parting, which can make it susceptible to damage from sharp blows. Its specific gravity ranges from 3.34 to 4.39. These properties are crucial for gemologists in identifying and distinguishing peridot from other green stones like tourmaline or chrome diopside.
Mining Locations
Peridot is sourced from several key locations around the globe, each producing stones with slightly different characteristics. The most famous historical source is the island of Zabargad (formerly Topazios) in the Red Sea, which has been mined for over 3,500 years. Today, significant sources include Pakistan, which produces large, high-quality crystals in the Koh-i-Noor mountains; Myanmar (Burma); and China. The San Carlos Apache Reservation in Arizona, USA, is also a notable source, particularly for smaller, commercial-grade stones. The gem found in the Lava fields of Hawaii is often called "Hawaiian Peridot" and is considered a symbol of the goddess Pele.
Spinel: The Great Impostor and a Jewel of Renewal
For centuries, spinel was the unsung hero of the gem world, often living in the shadow of more famous stones. Its most significant historical role was as a "great impostor," with red spinel being consistently mistaken for ruby. Some of the world's most famous "rubies" are, in fact, magnificent spinels. The Black Prince's Ruby, a massive 170-carat gem set in the British Imperial State Crown, and the Timur Ruby, both are spinels. It was not until 2016 that spinel was officially recognized as a modern birthstone for August, a long-overdue acknowledgment of its own intrinsic beauty and value. The name "spinel" is thought to derive from the Latin spina, meaning "thorn," a reference to the pointed shape of its natural crystals.
Spinel offers a remarkable diversity of color, making it a versatile and appealing choice for jewelry. Its palette includes vibrant reds, pinks, oranges, purples, and a range of blues, as well as black. This variety allows it to appeal to a wide range of tastes, from those seeking a classic ruby look to those desiring a unique, vibrant blue or pink gem. Beyond its aesthetic appeal, spinel is associated with themes of renewal, inspiration, and vitality. It is considered a high-energy stone, believed to restore energy, inspire hope, and provide encouragement during difficult times. Its history as a gem of royalty, worn by kings and emperors, lends it a modern style that is both timeless and sophisticated.
Gemological Properties of Spinel
Spinel is a magnesium aluminium oxide with the chemical formula MgAl₂O₄. It crystallizes in the cubic system and is prized for its exceptional clarity and brilliance. One of its most appealing attributes is its durability. With a Mohs hardness of 7.5 to 8, spinel is a tough and resilient gem, making it an excellent choice for all types of jewelry, including rings that are subject to daily wear.
Spinel is typically "eye-clean," meaning it lacks visible inclusions. Its refractive index is around 1.718, and it is singly refractive, similar to diamond and ruby. This property helps gemologists distinguish it from other stones. It has no cleavage, which adds to its toughness. Its specific gravity is approximately 3.58. While spinel is generally stable when exposed to light and chemicals, high heat can cause some colors to fade, and ultrasonic cleaners should be used with caution if the stone has fractures.
Mining Locations
Significant sources of spinel are found in Asia, particularly in the gem-rich regions of Myanmar (Burma), which has historically been the primary source for the finest red "ruby" spinels. Sri Lanka is another important source, producing a wide variety of colors. More recently, new deposits have been discovered that have expanded the availability of this gem. The Luc Yen region in northern Vietnam has been producing deep red, purple, pink, and vivid blue spinels since the 1980s and 2000s, respectively. A 2017 discovery in Tanzania yielded captivating pinkish and orangy-red spinels, along with purple and blue hues, further diversifying the market.
Sardonyx: The Ancient Stone of Strength and Protection
Sardonyx is the original August birthstone, with a history of use that dates back more than 4,000 years. It is a variety of chalcedony, which is a cryptocrystalline form of quartz, and is characterized by its distinctive banding. The name itself is a combination of "sard," a reddish-brown variety of chalcedony, and "onyx," which refers to the layered forms of quartz. Sardonyx features alternating layers of brownish-red to orange sard and typically white or black onyx, creating a beautiful, earthy, and banded appearance.
This gem has been a symbol of strength, courage, and protection since antiquity. It was a popular stone for Roman seals and signet rings because hot wax would not adhere to its surface. Roman soldiers wore sardonyx amulets engraved with images of heroes or gods, believing it would grant them courage and protection in battle. Its use as a talisman for stability, lasting happiness, and luck in love and marriage further underscores its role as a grounding and powerful stone. Its deep, earthy energy is considered protective and supportive for building stable relationships and personal fortitude.
Gemological Properties of Sardonyx
As a variety of chalcedony, sardonyx is composed of silicon dioxide (SiO₂) and has a trigonal crystal system. It is an opaque gem, valued for its striking bands rather than translucence or transparency. Its hardness on the Mohs scale is between 6.5 and 7, making it durable enough for jewelry, though it should be protected from hard impacts. Like other forms of chalcedony, it has no cleavage, which contributes to its suitability for carved items like cameos and intaglios.
Its luster is typically waxy to vitreous. The distinct bands of sard and onyx are its most defining feature, and skilled artisans often cut the stone to highlight these patterns in cameos, cabochons, and beads. The contrast between the reddish-brown layers and the white or black layers gives each piece of sardonyx a unique, organic character.
Mining Locations
Sardonyx has been sourced from various locations throughout history and continues to be mined today. Key sources include India, which is a major producer of banded chalcedony. Brazil also yields significant quantities, as do Germany and Uruguay. In the United States, sardonyx can be found in several states, contributing to the global supply of this ancient gem. Its widespread availability has made it a popular stone for both historical artifacts and contemporary jewelry.
Caring for Your August Birthstone Jewelry
Proper care is essential to maintain the beauty and longevity of any gemstone. Due to their differing properties, the three August birthstones require slightly different approaches to cleaning and storage.
Peridot Care: With a hardness of 6.5 to 7.0, peridot is the softest of the three and requires careful handling. It is susceptible to scratching and should be stored separately from harder stones. To clean peridot, use a soft-bristle brush with a solution of mild dish soap and warm water. Avoid harsh chemicals and sudden temperature changes, which could damage the gem. Ultrasonic cleaners are generally not recommended.
Spinel Care: Spinel is quite durable, rating 7.5 to 8 on the Mohs scale. It is generally safe to use ultrasonic and steam cleaners for spinel jewelry, provided the stone is free of significant fractures. As with all gems, warm soapy water and a soft brush are always a safe and effective cleaning method. Spinel is stable under normal light exposure, but high heat can cause some colors to fade.
Sardonyx Care: As a variety of chalcedony with a hardness of 6.5 to 7, sardonyx shares similar care requirements with peridot. It is best cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as the vibrations could potentially damage the stone or any settings. Store sardonyx jewelry carefully to prevent scratching by harder materials.
Conclusion
The August birthstones—peridot, spinel, and sardonyx—offer a compelling trio of choices that cater to diverse preferences for color, history, and symbolism. Peridot, with its celestial origins and cheerful green hue, represents vitality and protection. Spinel, the long-misunderstood jewel of royalty, provides a spectrum of vibrant colors and embodies renewal and inspiration. Sardonyx, the ancient guardian, offers grounding strength and courage through its distinctive earthy bands. Together, they form a complete and versatile group of gems that perfectly capture the warmth, strength, and enduring beauty of the summer month of August. For the gem enthusiast, jewelry buyer, or student of gemology, exploring these three stones reveals a rich story of geological wonder, human history, and cultural significance.