August is a unique month in the gemstone calendar, traditionally represented by the luminous green peridot. However, modern interpretations have expanded this choice, with many enthusiasts also embracing the vibrant spinel. This duality offers a fascinating study in the evolution of birthstone lists and the diverse beauty found within a single month. The following article delves into the history, properties, and cultural significance of these two August birthstones, drawing from a synthesis of gemological and historical data to provide a thorough guide for collectors, jewelers, and those born in the eighth month.
Historical and Cultural Significance
The tradition of associating specific gemstones with birth months has deep roots, though the official lists have evolved significantly over time. Historical records indicate that the concept can be traced back to the Breastplate of Aaron, a ceremonial garment described in the Book of Exodus, which was set with twelve stones representing the twelve tribes of Israel. Later, the first-century historian Josephus and the second-century philosopher St. Jerome drew connections between these twelve stones and the twelve signs of the zodiac, establishing an early link between gems and astrological periods. This ancient foundation laid the groundwork for the later development of birthstones.
The modern, standardized list of birthstones is a relatively recent creation. For centuries, lists varied by culture and region. A significant shift occurred in 1912 when the National Association of Jewelers (now the Jewelry Information Center) released the modern birthstone list. This list was created to suit contemporary tastes and ensure consistency in the jewelry trade, and it remains the primary reference for most jewelers today. While most months on this list have a single birthstone, some, like August, have seen additions. The official modern list for August is peridot, but the list also acknowledges spinel as an additional birthstone, reflecting a broader acceptance of gemstone variety.
Peridot itself holds a rich and often misunderstood history. For centuries, many of the world's most famous peridots were mistaken for emeralds. The most notable example is the large, 192.75-carat peridot gem housed at the Smithsonian Institution, which was originally thought to be an emerald. This gem was once part of the shrine of the Three Kings in Cologne Cathedral, a testament to its long-standing value and beauty. Historically, peridot has been mined since ancient times, with significant sources including the island of Zabargad (also known as St. John’s Island) in the Red Sea. Egyptian records from as early as 1500 B.C. describe peridot mining on this island, and the gems were often referred to as the "evening emerald" due to their ability to glow in low light. The Romans valued peridot for its protective qualities against evil spirits and nightmares, and it was often set in gold to enhance its perceived powers.
Spinel’s history is equally intertwined with mistaken identity. The term "spinel" comes from the Latin word spina, meaning thorn, referring to the sharp, crystal habits it often forms. For centuries, many of the world’s most famous "rubies" were actually spinel. The Black Prince’s Ruby, a massive 170-carat red gem that is part of the British Imperial State Crown, is a famous example of a spinel mistaken for a ruby. Similarly, the Timur Ruby, a 361-carat red gem that was once part of the Mughal imperial treasury, is also a spinel. These historical mix-ups underscore spinel’s remarkable beauty and durability, which allowed it to command the same respect as the finest rubies for centuries. While spinel was not part of the original 1912 list, its growing popularity and recognition as a distinct and valuable gemstone led to its inclusion as an alternative birthstone for August.
Geological Formation and Sources
Understanding the geological origins of a gemstone provides insight into its rarity and characteristics. Peridot is formed under unique conditions. It is one of the few gemstones that crystallizes in the Earth’s mantle, not in the crust. The primary source of peridot is magma, specifically in the Earth’s upper mantle. The gemstone’s formation occurs when magma from the mantle rises to the surface. As this magma cools, it releases gases, creating pockets called peridotite xenoliths. It is within these pockets that peridot crystals form. Peridot can also be found in lava rock, specifically in basalt flows, and in pallasite meteorites, which are stony-iron meteorites that contain crystals of peridot. The gemstone’s color is determined by its iron content; a higher concentration of iron results in a more yellow-green hue, while lower iron levels produce a purer green.
Peridot is mined in various locations worldwide, each contributing a unique character to the gemstones. The most historically significant source is the ancient peridot mine on the island of Zabargad in the Red Sea. This island was the primary source of peridot for the ancient world, and its gems are known for their exceptional quality. Other notable sources include Pakistan, which is known for producing large, high-quality peridot crystals; Myanmar (Burma), a region famous for its gemstones; and the United States, with peridot deposits found in Arizona (specifically the San Carlos Apache Reservation), New Mexico, and Hawaii. Australia, Brazil, China, Kenya, Mexico, Norway, Sri Lanka, and Tanzania also contribute to the global supply of peridot.
Spinel, in contrast, forms under a variety of geological conditions. It is commonly found in metamorphic rocks, such as marble, where it forms from the alteration of magnesium-rich rocks. It can also be found in alluvial deposits, where it has been eroded from its original source rock and transported by water. Spinel’s chemical formula is MgAl₂O₄, and its color is influenced by trace elements like iron, chromium, and cobalt. The red and pink varieties, which are most prized, get their color from chromium, similar to ruby. The most famous source for fine red spinel is the Badakhshan region in Afghanistan, which has supplied these gems for centuries. Other significant sources include Sri Lanka, which produces a wide range of spinel colors; Myanmar, known for its vibrant reds; and Vietnam, which has emerged as a source for high-quality spinel. Tajikistan and Thailand are also notable producers.
Gemological Properties
The physical and chemical properties of a gemstone determine its durability, appearance, and value. The following table summarizes the key gemological properties of peridot and spinel, based on data from authoritative gemological sources.
| Property | Peridot | Spinel |
|---|---|---|
| Chemical Formula | (Mg, Fe)₂SiO₄ | MgAl₂O₄ |
| Crystal System | Orthorhombic | Cubic |
| Hardness (Mohs Scale) | 6.5 - 7 | 8 |
| Refractive Index | 1.64 - 1.68 | 1.712 - 1.762 |
| Specific Gravity | 3.27 - 3.48 | 3.58 - 3.61 |
| Luster | Vitreous (glassy) | Vitreous (glassy) |
| Typical Colors | Olive green, brownish-green | Red, pink, orange, purple, blue, black, white |
Peridot is a member of the olivine mineral family. Its hardness on the Mohs scale ranges from 6.5 to 7, making it moderately durable but susceptible to scratching if worn daily without care. Its specific gravity is relatively high for a non-opaque gem, contributing to its perceived weight. The refractive index is moderate, giving peridot a good brilliance when well-cut. The most valued color for peridot is a pure, rich olive green, free from brown or yellow overtones. Clarity is generally good, though peridot can sometimes contain "lily pads"—small, plate-like inclusions that are characteristic of the stone. Peridot is not typically treated, as its color is natural and stable.
Spinel is an exceptionally durable gemstone, with a hardness of 8 on the Mohs scale. This makes it more resistant to scratching and wear than peridot, and even harder than quartz. Its cubic crystal system often results in well-formed, sharp-edged crystals. Spinel has a high refractive index and strong dispersion (fire), which gives it a brilliant sparkle, especially in well-cut faceted stones. The specific gravity is also high, making it feel substantial. While red is the most classic and valuable color, spinel occurs in a breathtaking array of hues, including vivid pinks, oranges, purples, blues, and even black. Most spinel is not treated, and its natural colors are highly prized. The gem’s excellent hardness and lack of cleavage make it an ideal choice for all types of jewelry, including rings and bracelets that are subject to daily wear.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, gemstones have long been imbued with symbolic meaning and metaphysical properties. These beliefs, while not scientifically proven, form a significant part of the cultural heritage surrounding birthstones.
Peridot has been associated with light, protection, and prosperity for millennia. The ancient Egyptians called it the "gem of the sun," believing it protected its wearer from the darkness and evil spirits. Its green color, reminiscent of spring, has led to associations with renewal, growth, and vitality. In modern crystal healing, peridot is often linked to the heart chakra, believed to promote emotional balance, compassion, and forgiveness. It is also considered a stone of abundance and good fortune, thought to attract wealth and success. For those born in August, peridot is said to embody the qualities of strength, purpose, and clarity, helping to clear negative emotions and bring joy and light into one’s life.
Spinel, with its history as a "great imposter," carries a unique symbolism of resilience and distinction. Because it was so often mistaken for ruby, it is sometimes associated with nobility and royalty, embodying a quiet strength and hidden value. The vibrant red and pink varieties are linked to passion, energy, and love, while blue spinel is associated with tranquility and peace. In metaphysical traditions, spinel is believed to be an energizing stone that can revitalize the body and mind. It is thought to reduce stress and fatigue, providing a boost of physical and mental energy. For August-born individuals, spinel is said to inspire hope, joy, and a renewed sense of purpose, helping to overcome obstacles with grace and determination.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone jewelry. The specific care requirements for peridot and spinel are dictated by their physical properties, particularly their hardness and stability.
Peridot, with a hardness of 6.5 to 7, is moderately durable but can be scratched by harder materials. It is not as tough as some other gems due to its cleavage properties. Therefore, it requires gentle handling. To clean peridot jewelry, use a soft brush, warm water, and a mild dish soap. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone or its setting. It is also advisable to remove peridot jewelry before engaging in physical activities, household chores, or swimming, to prevent impacts and exposure to abrasive substances. When storing peridot, keep it separate from other jewelry to avoid scratches.
Spinel, with a hardness of 8, is one of the most durable gemstones and is excellent for everyday wear. It is resistant to scratching and does not have cleavage, making it less prone to breaking from impacts. Cleaning spinel is straightforward: it can be safely cleaned with warm soapy water and a soft brush. It is also generally safe for ultrasonic cleaning, but it is always best to check with a professional jeweler first, especially if the spinel is set in a delicate or intricate piece. As with any gemstone, avoid sudden temperature changes and harsh chemicals. Storing spinel jewelry separately in a soft pouch or lined box will help preserve its polish and prevent contact with other gems.
Conclusion
The August birthstones, peridot and spinel, offer a compelling narrative of geological wonder, historical intrigue, and enduring beauty. Peridot, with its ancient origins in the Earth’s mantle and its luminous green glow, carries a legacy of protection and renewal, famously mistaken for emeralds in royal collections. Spinel, the resilient and vibrant gem, has a history of being mistaken for rubies, yet it stands on its own as a gem of exceptional hardness and a spectacular spectrum of colors. Together, they represent the diverse choices available to those born in August, blending tradition with modern appreciation. Whether drawn to the classic olive green of peridot or the brilliant hues of spinel, the wearer of an August birthstone carries a piece of the Earth’s deep history and a symbol of personal significance. Their enduring appeal lies in a perfect combination of scientific intrigue, cultural depth, and undeniable aesthetic charm, making them timeless treasures for generations.