The month of August is uniquely represented in the world of birthstones by not one, but three distinct gemological choices: peridot, spinel, and sardonyx. This trio offers a remarkable spectrum of color, durability, and historical significance, providing those born in the eighth month with a variety of options that cater to different tastes and preferences. While peridot is traditionally the primary birthstone, the inclusion of spinel and sardonyx as alternatives reflects the evolving nature of birthstone lists and the desire for personalization in modern jewelry. Each of these gems possesses unique characteristics, from peridot’s vibrant lime green to spinel’s dazzling array of colors and sardonyx’s layered, banded appearance. This article will delve into the history, geological origins, gemological properties, and cultural symbolism of these three August birthstones, providing a comprehensive guide for enthusiasts, collectors, and anyone interested in the science and lore behind these captivating minerals.
Historical Significance and the Evolution of August's Birthstones
The tradition of associating specific gemstones with each month has a complex history, with lists evolving over centuries. The modern concept of birthstones largely stems from a 1912 list adopted by the American National Association of Jewelers (Jewelers of America), which standardized the stones for commercial and cultural purposes. For August, this list originally included peridot. However, historical records and older traditions reveal a more varied picture.
Peridot has a long and storied history. It is believed to have been mined for over 3,500 years on the island of Zabargad (St. John’s Island) in the Red Sea, as documented by ancient Egyptian records. The Egyptians referred to peridot as the "gem of the sun," believing it protected its wearer from the terrors of the night and could ward off evil spirits. This green gem was not only a favorite of the ancient Egyptians but was also cherished by the Romans, who called it "topazion," a name that later caused confusion with the gemstone topaz. The name "peridot" itself is derived from the Arabic word "faridat," meaning gem. Its historical significance is further highlighted by its presence in the treasures of the Spanish Crown and its use in medieval European churches, often mistaken for emeralds due to its similar hue.
Spinel, the second modern birthstone for August, has a history often intertwined with that of ruby and sapphire. For centuries, large red spinels were mistaken for rubies, leading to their inclusion in royal regalia. The most famous example is the "Black Prince's Ruby," a 170-carat red spinel that has been part of the British Crown Jewels since the 14th century. Similarly, the "Timur Ruby," a 361-carat red spinel, is another historic piece once thought to be a ruby. The distinct identity of spinel as a separate mineral was only firmly established in the late 18th century, but its beauty and durability have ensured its place in history and, more recently, as a recognized birthstone.
Sardonyx, the traditional birthstone for August, boasts an even more ancient lineage. As a banded variety of chalcedony (a microcrystalline form of quartz), sardonyx has been used for over 2,000 years, particularly for carving cameos and intaglios. The Romans and Greeks highly valued sardonyx for its ability to be carved into intricate designs, taking advantage of its layered bands of color—typically white, black, orange, red, or brown. Cameos cut from sardonyx were popular in jewelry and were believed to offer protection. The use of sardonyx in signet rings for sealing documents was also widespread, as the stone could be easily engraved and provided a clear, durable impression.
The inclusion of spinel and sardonyx alongside peridot in modern birthstone lists demonstrates a shift towards offering more choices. While peridot remains the primary stone, spinel is often cited as a modern alternative, valued for its durability and color range, and sardonyx is recognized as the traditional stone. This triad allows for personal expression, with each stone carrying its own historical weight and cultural narrative.
Geological Formation and Global Sources
The three August birthstones originate from vastly different geological environments, which influence their availability and characteristics.
Peridot: Peridot is the gem-quality variety of the mineral olivine, specifically forsterite-rich in composition. It forms deep within the Earth's mantle and is brought to the surface through volcanic activity. Unlike many gemstones that form in the crust, peridot is found in igneous rocks and can be discovered in lava flows and even in meteorites (as a rare occurrence). The most significant historical source is the island of Zabargad in the Red Sea, which was mined by ancient Egyptians. Today, the primary commercial sources include Pakistan (notably the Kohistan region), the United States (Arizona, New Mexico, and Hawaii), Mexico, Brazil, Australia, Norway, and South Africa. The Arizona peridot mines, located on the San Carlos Apache Reservation, are a major source of gem-quality peridot in the United States, producing stones with a characteristic golden-green hue.
Spinel: Spinel is a magnesium aluminum oxide (MgAl₂O₄) that forms in metamorphic rocks, particularly in marble and in contact zones between igneous and sedimentary rocks. It can also be found in alluvial deposits, where water has eroded and transported the crystals. Historically, the most famous source of red spinel was the Badakhshan region of Afghanistan, which supplied the large stones for royal jewels. Today, key sources include Myanmar (Burma), which produces vibrant red and pink spinels; Sri Lanka, known for a wide range of colors including blue and purple; Vietnam, which yields high-quality red and pink spinels; and Tanzania, which is a significant source of blue spinel. Spinel is also mined in Tajikistan, Russia, and the United States (New York and North Carolina).
Sardonyx: Sardonyx is a variety of chalcedony, which is composed of silicon dioxide (SiO₂) with a cryptocrystalline structure. It forms in volcanic and sedimentary environments, typically in nodules or geodes. The banded patterns result from variations in the deposition of silica and iron oxides over time. Major sources of sardonyx include Brazil, India, Germany, the United States (Arizona, California, and Oregon), and Madagascar. The quality of sardonyx is determined by the sharpness and contrast of its bands, with the finest specimens showing clear, parallel lines of color.
Gemological Properties: A Comparative Analysis
Understanding the physical and chemical properties of these gems is essential for identification, valuation, and care. The following table summarizes key gemological data for peridot, spinel, and sardonyx, based on standard references.
| Property | Peridot | Spinel | Sardonyx |
|---|---|---|---|
| Chemical Formula | (Mg, Fe)₂SiO₄ | MgAl₂O₄ | SiO₂ (microcrystalline quartz) |
| Crystal System | Orthorhombic | Cubic | Trigonal (macrocrystalline quartz is hexagonal, but chalcedony is microcrystalline) |
| Mohs Hardness | 6.5 - 7 | 8 | 7 |
| Refractive Index | 1.654 - 1.690 | 1.718 | 1.53 - 1.54 |
| Specific Gravity | 3.34 - 4.39 | 3.58 - 3.61 | 2.58 - 2.64 |
| Color Range | Olive to lime green, brownish-green | All colors (red, pink, blue, purple, black, white) | Banded white, black, orange, red, brown |
| Typical Treatments | Heat treatment to reduce brownish tones | Heat treatment to improve color and clarity | None (natural color bands) |
Peridot: Peridot's hardness of 6.5 to 7 on the Mohs scale makes it reasonably durable for most jewelry, though it can be susceptible to scratching if worn daily against harder materials. Its refractive index is relatively high for a non-quartz gem, contributing to its good brilliance. A unique characteristic of peridot is its dichroism, where the stone may show slightly different shades of green when viewed from different crystal directions. Peridot is typically not heated, as its color is generally stable, though some stones may be oiled or waxed to improve surface appearance.
Spinel: Spinel's exceptional hardness of 8 on the Mohs scale makes it one of the most durable gemstones, rivaling topaz and surpassing emerald and peridot. This durability, combined with its high refractive index and strong dispersion (fire), gives spinel a remarkable brilliance and sparkle. Spinel is almost always untreated, though heat treatment is sometimes used to enhance the color of certain varieties (e.g., transforming brownish stones to blue). Its cubic crystal system gives it a single refractive index, which distinguishes it from many other gemstones.
Sardonyx: As a variety of chalcedony, sardonyx has a lower hardness (7) and refractive index compared to peridot and spinel. It is typically cut en cabochon (a smooth, rounded dome) or used for carving, as its banded structure is best displayed in these forms. The stone's opacity and layered appearance are its defining features. Sardonyx is not treated, as its value lies in its natural banding. Its lower hardness makes it more susceptible to scratches than spinel, but it is still suitable for jewelry like earrings, pendants, and occasional-wear rings.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, all three August birthstones are steeped in symbolism and metaphysical lore, which have been passed down through generations.
Peridot: Known as the "gem of the sun," peridot has long been associated with light, warmth, and protection. Ancient Egyptians believed it could ward off evil spirits and protect against nightmares. In medieval Europe, it was thought to have healing properties, particularly for the heart and lungs. Modern metaphysical beliefs attribute peridot with the ability to promote growth, abundance, and prosperity, as well as to alleviate stress and jealousy. It is also linked to the heart chakra, encouraging compassion and forgiveness.
Spinel: Historically, red spinel was often associated with royalty and power due to its resemblance to ruby, the "king of gems." It is believed to revitalize and energize the wearer, promoting physical and mental stamina. Different colors of spinel are said to have specific properties: red for passion and courage, blue for clarity and communication, and pink for love and compassion. Overall, spinel is considered a stone of renewal and rejuvenation, helping to overcome lethargy and inspire new goals.
Sardonyx: With its ancient use in cameos and signet rings, sardonyx has long been a symbol of protection and courage. It was believed to bring stability, happiness, and marital bliss. In ancient Rome, it was associated with the god Mars and was used to make amulets for soldiers, believed to grant strength and protection in battle. Modern interpretations suggest that sardonyx enhances self-confidence, discipline, and clear communication. It is also thought to be a grounding stone that connects the wearer to the Earth's energy.
Care and Cleaning: Preserving the Beauty of August's Gems
Proper care is essential to maintain the longevity and appearance of these birthstones. Their varying hardness and cleavage properties dictate different maintenance requirements.
Peridot: With a hardness of 6.5-7, peridot is moderately durable. It can be cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, as sudden temperature changes can cause fractures. Peridot is also sensitive to acids and harsh chemicals, so it should be removed before household cleaning. Due to its cleavage (a tendency to break along certain planes), it should be protected from sharp blows.
Spinel: As one of the hardest and most durable gemstones (hardness 8), spinel is very low-maintenance. It can be safely cleaned with warm, soapy water, an ultrasonic cleaner, or a steam cleaner. Its toughness makes it resistant to chipping and breaking, making it an excellent choice for everyday jewelry like engagement rings. However, as with all gemstones, it is best to avoid sudden extreme temperature changes.
Sardonyx: With a hardness of 7, sardonyx is relatively durable but can be scratched by harder materials. It should be cleaned with a soft, damp cloth and mild soap. Avoid ultrasonic cleaners and harsh chemicals, as they can damage the stone's surface or affect any treatments. Since sardonyx is often carved or set in intricate settings, gentle cleaning is recommended to preserve its details.
Conclusion
The birthstones for August—peridot, spinel, and sardonyx—offer a remarkable diversity that reflects the rich tapestry of gemology. From the ancient, sun-kissed greens of peridot to the dazzling, durable spectrum of spinel and the ancient, banded artistry of sardonyx, each stone carries a unique legacy. Their geological origins span the globe, from volcanic depths to metamorphic formations and sedimentary deposits. Their gemological properties provide a range of durability suitable for various jewelry applications, with spinel standing out for its exceptional hardness. Symbolically, they are united by themes of protection, vitality, and clarity, yet each contributes its own cultural narrative. For those born in August, this trio provides not just a birthstone, but a choice of personal expression, connecting them to millennia of human history and the enduring wonders of the natural world.