The month of August boasts a trio of exceptional birthstones, offering a remarkable diversity in color, durability, and historical significance. The primary birthstones for August are spinel, sardonyx, and peridot. Each gemstone presents a unique character, from the vibrant reds and blues of spinel to the ancient, banded patterns of sardonyx and the lush green of peridot. This guide delves into the geological origins, gemological properties, historical lore, and practical care for these three captivating gems, providing a detailed resource for enthusiasts, collectors, and anyone born in the eighth month of the year.
History and Lore
The tradition of assigning specific gemstones to birth months is a practice that has evolved over centuries, with roots in various cultural and religious texts. The modern birthstone list, particularly for August, reflects this historical layering, incorporating ancient beliefs with contemporary gemological understanding.
Spinel, while often mistaken for ruby or sapphire throughout history due to its similar appearance, has a distinct identity. Historically, many famous "rubies," such as the Black Prince's Ruby in the British Imperial State Crown, were later identified as red spinel. This misidentification contributed to its long-standing presence in royal and ceremonial jewelry. The gemstone’s reputation for durability and its wide spectrum of colors have made it a prized material for centuries. Its recognition as a birthstone enhances its profile, moving it from a gem often overshadowed by its more famous counterparts to a celebrated gem in its own right.
Sardonyx is one of the oldest gem materials used in jewelry and adornment. This banded variety of chalcedony has been utilized for over two millennia, particularly for creating cameos and intaglios. The most prized examples feature sharp, parallel bands of white, black, orange, red, or brown. Ancient civilizations, including the Romans and Greeks, valued sardonyx for its workability and the striking contrast in its bands, which allowed artisans to create detailed relief carvings. Its use in signet rings and amulets speaks to its long-standing role in both personal and ceremonial adornment.
Peridot, with its distinctive olive-green hue, has a history that stretches back to ancient Egypt. Often called the "evening emerald" due to its glow in low light, peridot was mined on the island of Zabargad (now St. John's Island) in the Red Sea as early as 1500 B.C. Egyptian priests used peridot jewelry in their rituals, and it was believed to be a favorite gem of Cleopatra. The gemstone was also highly regarded in medieval Germany, where it was often confused with emerald. Its status as a birthstone for August solidifies its place among the more recognized green gems.
The assignment of these three gemstones to August is a product of the 1912 list established by the National Association of Jewellers (now the Jewellers of America), which standardized birthstones for the United States. This list has been updated over time, but spinel, sardonyx, and peridot remain the official birthstones for August, offering a choice that caters to different tastes and budgets.
Geological Formation and Sources
Understanding the geological origins of these birthstones reveals the diverse processes that create such beautiful minerals.
Spinel forms in metamorphic rocks, particularly in magnesium-rich environments. It is commonly found in alluvial deposits, where weathering has broken down the host rock, allowing the durable spinel crystals to concentrate in riverbeds and sediments. Major sources of spinel include Myanmar (Burma), which is renowned for its vibrant red and blue specimens, as well as Sri Lanka, Vietnam, and Tanzania. The gem’s formation often occurs alongside other minerals like corundum (ruby and sapphire) and zircon, which can lead to the historical confusion between these gems.
Sardonyx is a variety of chalcedony, which itself is a microcrystalline form of quartz (silicon dioxide, SiO₂). It forms in volcanic and sedimentary rocks, where silica-rich solutions fill cavities and slowly crystallize over time. The distinctive banding is created by successive layers of different colored chalcedony—typically sard (brownish-red) and onyx (black or white)—that develop in alternating sequences. Significant sources of sardonyx include India, Brazil, Germany, and the United States (particularly in Oregon and Idaho). The quality of the banding and the sharpness of the color contrasts determine the gem’s value for carving and jewelry.
Peridot is one of the few gemstones formed deep within the Earth’s mantle and brought to the surface by volcanic activity. It is a variety of the mineral olivine (Mg, Fe)₂SiO₄, with its green color resulting from the presence of iron. Peridot is found in mafic and ultramafic igneous rocks, such as basalt and peridotite. Major commercial sources include the United States (Arizona and New Mexico), Pakistan, Myanmar, and the Red Sea island of Zabargad. The gem’s formation under high temperature and pressure conditions results in crystals that can be relatively large, making peridot a popular choice for statement jewelry pieces.
Gemological Properties
The durability and appearance of a gemstone are defined by its physical and chemical properties. The table below summarizes key gemological characteristics for the August birthstones based on available data.
| Gemstone | Chemical Composition | Hardness (Mohs Scale) | Key Properties | Durability Rating |
|---|---|---|---|---|
| Spinel | MgAl₂O₄ | 8 | Single refractive index; excellent durability; occurs in a wide range of colors including red, blue, pink, and black. | Very Good to Excellent |
| Sardonyx | SiO₂ (Quartz variety) | 7 | Microcrystalline quartz; banded appearance; often cut as cabochons or carved. | Good |
| Peridot | (Mg, Fe)₂SiO₄ | 6.5 - 7 | Double refractive index; prone to abrasion; susceptible to cracking from sudden temperature changes. | Fair to Poor |
Spinel is renowned for its exceptional durability. With a hardness of 8 on the Mohs scale, it is highly resistant to scratching and wear. Its toughness is also excellent, meaning it can withstand impact without fracturing easily. This makes spinel an outstanding choice for all types of jewelry, including engagement rings, where daily wear is expected. The gem is singly refractive, meaning light enters and exits the stone without splitting, which can be a distinguishing feature from other gems like sapphire.
Sardonyx, as a variety of quartz, has a hardness of 7. While durable enough for most jewelry applications, it is softer than spinel and can be scratched by harder materials. Its banded structure makes it ideal for cabochon cuts that highlight the parallel lines, or for intricate carving. The lack of cleavage in quartz means it is less prone to breaking along planes, but it can still be damaged by sharp blows.
Peridot has a hardness ranging from 6.5 to 7, making it moderately durable. However, it is more vulnerable to abrasion and scratching than spinel or sardonyx. Peridot also has perfect cleavage in two directions, which means it can split cleanly if struck with sufficient force. Additionally, peridot is sensitive to rapid temperature changes, which can cause internal stress and cracking. These properties dictate that peridot jewelry should be handled with care, especially in settings like rings or bracelets that are exposed to potential impacts.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each of the August birthstones carries a rich tapestry of symbolic meanings and metaphysical beliefs, often tied to their color and historical use.
Spinel is associated with revitalization and renewal. Its vibrant colors are thought to inspire passion and energy, with red spinel symbolizing love and commitment, and blue spinel representing wisdom and tranquility. Historically, it was believed to protect against poison and to promote physical and spiritual healing. As a birthstone, spinel is said to bring its wearer vitality and a renewed sense of purpose.
Sardonyx, with its ancient origins, is deeply connected to themes of strength and protection. In Roman times, it was believed to protect the wearer from harm and to bring courage. The contrasting bands of color were seen as a symbol of balance between light and dark, or between the physical and spiritual realms. As a birthstone, sardonyx is thought to enhance willpower and discipline, making it a stone for those seeking stability and resilience.
Peridot, known as the "gem of the sun," is associated with light, growth, and prosperity. Ancient Egyptians believed it was a stone of the sun, capable of warding off nightmares and evil spirits. It is often linked to the heart chakra, promoting emotional balance and compassion. Peridot is also said to attract abundance and success, making it a popular choice for those seeking to manifest their goals. As a birthstone, it is believed to bring good health, restful sleep, and peace to relationships.
Care and Cleaning
Proper maintenance is essential to preserve the beauty and longevity of any gemstone jewelry. The care requirements for the August birthstones vary based on their distinct properties.
Spinel is relatively easy to care for due to its high hardness and toughness. It can be safely cleaned using warm water, a mild detergent, and a soft brush. Ultrasonic and steam cleaners are generally safe for spinel, but it is always prudent to inspect the jewelry for any loose settings or fractures before using these methods. Storing spinel jewelry separately from other gems will prevent scratching.
Sardonyx can be cleaned with warm, soapy water and a soft cloth or brush. Avoid using harsh chemicals or abrasive cleaners, as they can damage the surface. While sardonyx is relatively stable, it is best to avoid extreme temperature changes. Ultrasonic cleaners are typically safe for sardonyx, but caution is advised if the stone is part of a complex carving or set in a delicate mounting.
Peridot requires the most careful handling among the three. It should be cleaned only with warm, soapy water and a soft brush. Do not use ultrasonic cleaners or steam cleaners for peridot, as the vibrations and heat can cause fractures or worsen existing cleavage planes. It is also advisable to remove peridot jewelry before engaging in activities that could subject it to impact or abrasion, such as sports or heavy manual work. When storing, keep peridot separate from harder gems to avoid scratches, and consider wrapping it in a soft cloth to protect it from dust and damage.
Conclusion
The birthstones of August—spinel, sardonyx, and peridot—offer a compelling range of options that cater to diverse preferences, from the durable and vibrant spinel to the ancient, banded sardonyx and the luminous green of peridot. Each gemstone is distinguished by its unique geological history, gemological properties, and cultural significance. Spinel’s exceptional durability and wide color palette make it an excellent choice for everyday jewelry, while sardonyx’s historical legacy as a carving material provides a connection to ancient artistry. Peridot, with its captivating green hue and association with light and growth, continues to charm with its unique formation story. Understanding the characteristics and care requirements of these gems allows individuals to make informed choices, ensuring that their August birthstone jewelry remains a treasured possession for years to come.