August is a unique month in the world of birthstones, offering not one, but three distinct and officially recognized gems: peridot, spinel, and sardonyx. This trio provides a remarkable spectrum of color, history, and lore, reflecting the vibrant energy of summer. While sardonyx holds the title of the traditional and original birthstone for the month, peridot was added in the early 20th century, and spinel joined the official list more recently in 2016. Together, they present a fascinating study in gemological diversity, from the volcanic and extraterrestrial origins of peridot to the centuries-long case of mistaken identity that plagued spinel and the ancient, banded beauty of sardonyx. This article delves into the history, geological formation, gemological properties, and cultural significance of these three remarkable stones, offering a comprehensive guide for enthusiasts, collectors, and anyone born in the eighth month of the year.
History and Lore
The history of August's birthstones is a layered narrative, with each stone carrying a legacy that spans millennia. Sardonyx, the oldest of the three, boasts a history dating back more than 4,000 years. As the original August birthstone, it was highly valued in ancient Rome, where it was commonly used for signet rings. The stone's name derives from the Greek "sardios," referring to the reddish-brown sard, and "onyx," meaning nail or claw, likely alluding to its banded appearance. Its durability made it a favorite for carving cameos and intaglios, where its distinct bands of color could be artfully utilized to create contrast and detail.
Peridot's history is equally ancient, with its origins shrouded in historical confusion. For centuries, peridot was often mistaken for other precious green gems, most notably emerald. Some historians speculate that Cleopatra's famous emerald collection may have actually been comprised of peridot. This confusion extended to other gems as well; the Red Sea island of Topazios, a purported source of the name "topaz," actually produced peridot. A famous example of this historical misidentification can be seen in Germany's Cologne Cathedral. The Shrine of the Three Holy Kings is decorated with 200 carats of gems that were long believed to be emeralds but are now known to be peridot. The word "peridot" itself is believed to come from the Arabic "faridat," meaning gem, a fittingly simple name for a stone prized across many ancient and medieval cultures.
Spinel's history is defined by a long and dramatic case of mistaken identity. For centuries, red spinel was confused with ruby, with some of the world's most famous "rubies" actually being spinel. The most notable example is the Black Prince's Ruby, a massive red stone that adorns the British Imperial State Crown. This stone, along with the Timur Ruby, is actually a spinel. This centuries-long confusion meant that spinel was often underappreciated in its own right, valued only as an imitation of the more coveted ruby. It wasn't until the 20th century that gemologists began to distinguish spinel as a unique mineral species with its own distinct properties and beauty. In 2016, the American Gem Trade Association (AGTA) and Jewelers of America (JA) officially added spinel to the list of August birthstones, finally giving this "hidden gem" the recognition it deserves.
The addition of these stones to the official birthstone list reflects a historical evolution. Originally, sardonyx was the sole birthstone for August. Peridot was added in 1912, likely due to its growing popularity and wider availability. Spinel's inclusion in 2016 was a modern update, aimed at providing more affordable and accessible alternatives, as well as spotlighting a lesser-known but stunning gem.
Geological Formation and Sources
The three August birthstones originate from dramatically different geological environments, contributing to their unique characteristics.
Peridot is formed under extreme conditions. Unlike many gemstones that crystallize in the Earth's crust, peridot forms in the upper mantle, the layer between the crust and the core. It is brought to the surface by volcanic activity, often found in hardened lava. Its formation in the mantle is evidenced by its discovery in certain types of volcanic rocks. Perhaps most intriguingly, peridot has also been found in meteorites that have traveled from outer space, making it one of the few gems not originating from the Earth's crust. The oldest-recorded source of peridot is the Egyptian island of Zabargad (also known as St. John's Island) in the Red Sea. This source was exploited as early as the second century B.C. and remained a primary source for many years. Other significant modern mining sites include China, Myanmar (Burma), Pakistan, Tanzania, Vietnam, and the United States (particularly in Arizona and New Mexico).
Spinel forms in metamorphic rocks, particularly in limestone that has been subjected to intense heat and pressure. It is often found in alluvial deposits, where it has been eroded from its host rock and carried by water. Historically, the most famous sources for red spinel were in Southeast Asia, particularly in the border regions of what is now Afghanistan, Tajikistan, and Burma (Myanmar). The mines of Badakhshan in Afghanistan were the source of the large spinels that were mistaken for rubies in royal crowns. Today, spinel is also mined in Sri Lanka, Vietnam, and parts of Africa. Its occurrence is less common than many other gems, which contributes to its status as a "hidden gem."
Sardonyx is a variety of banded chalcedony, which is a microcrystalline form of quartz (silicon dioxide, SiO₂). It forms in volcanic or sedimentary environments, where silica-rich solutions deposit layers of chalcedony in cavities or fissures. The distinct bands of color—typically red or brown sard alternating with white or black onyx—are created by variations in the iron oxide content and other impurities during the deposition process. Major sources for sardonyx include India, where it has been mined for centuries, as well as Brazil, Germany, and the United States. Its formation process makes it relatively abundant, contributing to its historical use in carved objects and jewelry.
Gemological Properties
Understanding the physical and chemical properties of these stones is essential for identification, valuation, and care. The following table summarizes the key gemological characteristics of peridot, spinel, and sardonyx as derived from the provided sources.
| Property | Peridot | Spinel | Sardonyx |
|---|---|---|---|
| Mineral Family | Olivine | Spinel | Chalcedony (Quartz) |
| Chemical Formula | (Mg,Fe)₂SiO₄ | MgAl₂O₄ | SiO₂ (with iron oxide impurities) |
| Crystal System | Orthorhombic | Cubic | Hexagonal (microcrystalline) |
| Hardness (Mohs Scale) | 6.5 - 7 | 8 | 6.5 - 7 |
| Refractive Index | 1.635 - 1.690 | 1.718 | 1.535 - 1.539 |
| Specific Gravity | 3.27 - 4.37 | 3.58 - 3.61 | 2.58 - 2.64 |
| Color | Yellowish green to greenish yellow; shades from chartreuse to deep olive. | Wide range: vivid red (most prized), pink, orange, purple, blue, black. | Bands of red, brown, and white (or black). |
| Transparency | Transparent to translucent | Transparent to opaque | Translucent to opaque |
| Luster | Vitreous (glassy) | Vitreous | Vitreous to waxy |
Peridot is the gem variety of the mineral olivine. Its distinctive green color comes directly from the presence of iron within its crystal structure, unlike many other colored gems where the hue is caused by trace elements. The amount of iron determines the intensity of the green, ranging from light yellow-green to a deep olive. Peridot has a hardness of 6.5 to 7 on the Mohs scale, making it suitable for most types of jewelry but requiring some care to avoid scratches from harder materials. It is typically free of inclusions, and any visible ones are often small, liquid inclusions or tiny mineral crystals.
Spinel is a magnesium aluminum oxide. It is prized for its exceptional hardness (8 on the Mohs scale), which makes it very durable and resistant to scratching and abrasion. Its refractive index is higher than that of quartz, giving it a bright, lively sparkle. The most valued color is a vivid, pure red, often compared to a ruby, but its wide color range—including vibrant blues, pinks, and oranges—offers great versatility. Its specific gravity is relatively high, and it typically has good clarity, with few inclusions.
Sardonyx is a variety of chalcedony, which is composed of microcrystalline quartz (silicon dioxide). Its hardness is 6.5 to 7 on the Mohs scale, similar to peridot. The characteristic bands of color are the result of layers of sard (red or brown chalcedony) alternating with layers of onyx (white or black chalcedony). The specific gravity is lower than that of peridot and spinel, consistent with its quartz composition. Sardonyx is often opaque or translucent and is frequently carved or cut into cabochons to best display its banding.
Symbolism and Metaphysical Beliefs
Each of the August birthstones carries a rich tapestry of symbolic meanings and metaphysical beliefs, many of which have persisted from ancient times to the present day.
Peridot has long been associated with light, positivity, and the sun. Its vibrant green hue, reminiscent of fresh summer grass, is thought to bring feelings of joy, abundance, and confidence. In ancient times, it was believed to protect the wearer from nightmares and to ward off evil spirits. It is often called the "Gem of the Sun" because it was believed to possess the power of the sun, bringing warmth and life. In modern crystal healing, peridot is linked to the Heart Chakra, supporting emotional healing, opening the heart to love, and releasing negative patterns. Its association with prosperity and good fortune is so strong that it is often given as a gift for the sixteenth wedding anniversary.
Spinel is viewed as a stone of renewal and inspiration. Its wide array of colors lends itself to a variety of symbolic meanings. Red spinel, in particular, is associated with vitality, passion, and energy. It is believed to help restore energy, inspire hope, and provide encouragement through difficult times. Some traditions associate spinel with grounding and high-energy vibrations, making it a versatile stone for different intentions. Its royal history, tied to mistaken identity with rubies, adds a layer of symbolism related to regality, power, and the idea of a "hidden treasure" finally being revealed.
Sardonyx, with its earthy, banded appearance, is deeply associated with grounding, stability, and protection. As an ancient stone used for signet rings and cameos, it has a long history of being a talisman for strength, courage, and steadfastness. It is believed to support stable relationships and promote marital happiness. The bands of color are seen as representing different layers of strength and protection. In historical contexts, sardonyx was often worn as an amulet to guard against negative forces and to instill a sense of security and resilience.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone. The gemological properties of peridot, spinel, and sardonyx dictate specific care instructions.
Peridot has a hardness of 6.5 to 7, making it moderately durable. However, it can be susceptible to scratches and abrasions if not handled carefully. It is also somewhat sensitive to rapid temperature changes, which can cause fractures. To clean peridot, use warm, soapy water and a soft brush. Avoid harsh chemicals, ultrasonic cleaners, and steam cleaners, as these can damage the stone. It is best to store peridot jewelry separately to prevent it from being scratched by harder gems.
Spinel is one of the more durable gemstones, with a hardness of 8 on the Mohs scale. It is resistant to scratching and can withstand daily wear with minimal risk. Spinel is also stable when exposed to light and heat, making it relatively easy to care for. Cleaning can be done with warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe for spinel, but it is always advisable to check with a professional jeweler first, especially if the stone is set in a delicate piece.
Sardonyx, with a hardness of 6.5 to 7, requires similar care to peridot. As a form of chalcedony, it is durable but can be scratched by harder materials. It is also important to note that sardonyx can be dyed or treated to enhance its color, so it is essential to know the stone's treatment history. Cleaning should be done with warm, soapy water and a soft cloth. Avoid harsh chemicals and prolonged exposure to strong sunlight, which could potentially fade dyed stones. As with other gemstones, it is best to remove sardonyx jewelry before engaging in activities that could subject it to hard knocks or abrasive surfaces.
Conclusion
The trio of August birthstones—peridot, spinel, and sardonyx—offers a remarkable journey through gemological science, history, and symbolism. From the volcanic and celestial origins of peridot and its long history of being mistaken for emerald, to the centuries-long case of mistaken identity that defined spinel's royal legacy, and the ancient, banded artistry of sardonyx, each stone tells a unique story. Their diverse colors—from peridot's summer-green glow, to spinel's vibrant spectrum, and sardonyx's earthy bands—provide a wide palette for personal expression. Their differing hardness and durability offer options for various jewelry styles and lifestyles. For those born in August, these stones are more than just gems; they are a connection to a rich past, a celebration of geological wonder, and a personal talisman of summer's warmth, strength, and light.