August's birthstone gemstones, peridot, spinel, and sardonyx, each possess a rich history and unique set of properties that have captivated people for centuries. These three stones, now officially designated as the official birth gemstones for August by the modern jewelry industry, have been used in jewelry, adornment, and even protective talismans across different civilizations and time periods.
From the vivid green of peridot, with its cosmic origin, to the diverse colors of spinel and the contrasting banding patterns of sardonyx, each gemstone brings its own character and charm. This article delves into the geological makeup, historical uses, cultural associations, and practical considerations for caring for these August birthstones, presenting a comprehensive overview that combines scientific detail with cultural insight.
History and Lore
The use of gemstones as birthstones is a tradition that dates back to ancient times, with the earliest known references appearing in the Breastplate of Aaron, described in the Book of Exodus. While this early concept primarily associated each stone with a tribe of Israel rather than a month, the idea of linking gemstones to time and personal identity gradually evolved over the years.
The August birthstones are no exception, having carried their own stories and symbolism throughout history. Sardonyx is considered the oldest of the three and is one of the few gemstones with an unbroken history of use as a birthstone. Historically, it was worn in ancient Rome and was highly valued for its durability and clear contrast between its reddish and white layers. Roman statesmen used sardonyx in sealing wax, as the stone’s surface did not stick to the hot wax.
Peridot, on the other hand, has a more dramatic origin. Often found in volcanic lava and even in meteorites, peridot is one of the few gemstones that have an extraterrestrial source. The gemstone was first discovered on the island of Topazios in the Red Sea, a place that is now known as St. John’s Island. The island got its name from St. John’s Church, but in ancient times, the gem was known as the “gem of the sun.” The Ancient Egyptians believed that peridot was a sacred stone and had specific religious significance.
Spinel, the most recently added of the August birthstones, is often mistaken for other well-known gemstones such as ruby or even garnet. Its history is shrouded with misidentifications; for instance, the famous “Black Prince’s Ruby” in the Imperial State Crown of England was only identified as a spinel in the 18th century. This August gem has been admired for centuries by royal families and aristocrats alike.
Geological Formation and Sources
Understanding the formation and natural occurrence of these gemstones gives a deeper insight into their characteristics and allure.
Peridot
Peridot is a variety of the mineral olivine, with a chemical composition of magnesium iron silicate (Mg₂SiO₄ to Fe₂SiO₄). It is formed under extremely high temperatures and pressures, primarily in the Earth's mantle, at depths exceeding 300 kilometers. The magma that brings it up from these deep layers may carry the gemstone to the Earth's surface or deposit it within meteorites.
The most significant and recent sources of peridot are found in the United States, particularly in Arizona. Arizona produces between 80% and 95% of the world's supply of this gemstone. Other notable sources include Pakistan, China, and several islands in the Indian Ocean.
Spinels
The chemical composition of spinel is magnesium aluminum oxide (MgAl₂O₄), and because it can take on a wide range of colors depending on trace elements, it is often mistaken for other gemstones. While historically misidentified as ruby, spinel is now celebrated for its vibrant colors and clarity.
The sources for spinels are diverse and include countries such as Tajikistan, Myanmar, Sri Lanka, Vietnam, Tanzania, and Pakistan. Tanzania became particularly notable after the 2007 discovery of a unique red, pinkish, and purplish spinel.
Sardonyx
Sardonyx is a type of banded chalcedony, a microcrystalline form of quartz. Its formation is linked to sedimentary processes and the slow crystallization of silica over thousands of years. The reddish-brown color of the sard bands comes from iron oxide inclusions, while the white or black onyx layers contain no iron.
India is known for producing some of the finest sardonyx, particularly for its clear banding and strong color contrast. Other key sources include Brazil, Germany, Czech Republic, Slovakia, Madagascar, Uruguay, and the United States.
Gemological Properties
The gemological properties of these stones define their suitability for jewelry and their physical and optical characteristics.
Peridot
Peridot is distinct from other gemstones due to its color. It occurs in a spectrum from yellow-green to greenish-yellow and can appear bright and luminous. The color is due to its iron content. It has a refractive index of 1.65–1.69 and a birefringence of 0.036. Peridot is not found in any other color aside from its characteristic green, making it a truly unique gemstone.
The hardness of peridot on the Mohs scale is 6.5 to 7. It is relatively fragile compared to diamonds or sapphires, and it is susceptible to chipping or cracking if not handled properly. It also has perfect cleavage, meaning it can split easily along certain planes under stress.
Light dispersion and brilliance in peridot are moderate, contributing to its transparent and glassy appearance. Peridots are usually cut into round, oval, or faceted shapes to best showcase their color and refractive qualities.
Spinel
Spinel exhibits a refractive index of 1.718 and a birefringence of near zero. It displays excellent clarity and is known for its brilliance, particularly in deeper red shades. Spinel exists in an array of rich colors, including red, pink, orange, purple, blue, and even black. The most famous is the red spinel, which is often compared to ruby for its beauty and depth.
With a hardness of 8 on the Mohs scale, spinel is a durable gemstone suitable for everyday wear. It is also thermally stable, though prolonged exposure to high heat can sometimes dull its color.
| Gemstone | Hardness (Mohs) | Refractive Index | Color Range |
|---|---|---|---|
| Peridot | 6.5–7 | 1.65–1.69 | Yellow-green to greenish-yellow |
| Spinel | 8 | ~1.718 | Red, pink, orange, purple, blue, bluish green, and more |
| Sardonyx | 6.5 | ~1.53 | Banded red, brown, and white |
Spinel's optical properties make it ideal for faceting into brilliant cuts, and it is often compared to fine rubies and sapphires for its display of color and fire.
Sardonyx
Sardonyx is banded chalcedony, with refractive indices ranging between 1.53 and 1.54. It has a hardness of 6.5–7, making it harder than agate but more fragile than many other common gemstones. The clarity of sardonyx is generally opaque to semi-translucent, depending on the thickness and clarity of the bands.
One of the most distinctive features of sardonyx is its banding pattern. These layers are usually parallel and clearly demarcated, creating visually striking designs that are often used for cameos or signet rings.
Sardonyx gemstones are often carved rather than cut, as the banding and color variations provide a natural canvas for intricate designs. The stone has historically been used for intaglios and cameos, showcasing the craftsmanship of ancient jewelers.
Symbolism and Metaphysical Beliefs
Peridot
Peridot has been associated with a range of spiritual and emotional properties across different cultures. In historical times, the gemstone was believed to shield the wearer from evil and negative energies. Ancient Romans and Egyptians revered it as a talisman against nightmares and bad omens.
In modern times, peridot continues to symbolize inner peace, strength, and balance. It is often given as a gift to promote positive energy, harmonious relationships, and clarity of thought. According to modern beliefs, peridot also encourages creativity and inspires one to approach life with optimism.
One of the more unique aspects of peridot is its association with love—specifically, as a stone of eternal love. Some sources suggest that it may be worn by those in committed relationships to enhance passion and devotion.
Spinel
Spinel is often considered a “heart” stone, symbolizing warmth and compassion. Its ability to evoke a sense of calm and peace has led to its use in spiritual healing practices. Historically, red spinel was believed to combat blood loss and inflammation, and it was used in traditional medicine.
Symbolically, spinel is often associated with emotional stability and the promotion of harmonious relationships. Its variety of colors allows each shade to carry its own meaning—red for passion and vitality, pink for nurturing and love, and blue for clear communication and intelligence.
It is also widely known as the 22nd wedding anniversary gemstone, symbolizing deepening love, unwavering commitment, and enduring peace.
Sardonyx
Sardonyx has a long-standing reputation as a protective stone. In ancient Rome, it was often worn by warriors and politicians to protect themselves and their actions. The stone was believed to instill courage, strength, and decisiveness.
As a banded stone, sardonyx also symbolizes the balance between different aspects of life—such as activity and rest, ambition and patience, freedom and form. It is often used in meditation to help focus the mind and maintain emotional equilibrium.
In modern metaphysical beliefs, sardonyx is thought to be particularly useful in business and public affairs. It is said to grant the wearer confidence and assertiveness, while also protecting them from deceit and manipulation.
Care and Cleaning
Due to the physical characteristics of each gemstone, specific care instructions are necessary to preserve their beauty and durability.
Peridot
Peridot, with a hardness of 6.5–7, is a relatively fragile gemstone. It should be protected from hard impacts and sudden temperature changes. Exposure to heat or direct sunlight may cause discoloration over time.
Cleaning peridot should be done with warm soapy water and a soft brush. Ultrasonic and steam cleaners are not recommended, especially if the gemstone contains inclusions or is mounted in a way that traps moisture.
Avoid using abrasive cleaners or harsh chemicals, and do not polish it with compounds that might damage the surface or remove the stone's luster.
Spinels
Spinel is more resilient, with a hardness of 8 on the Mohs scale, making it suitable for everyday use in rings, pendants, and bracelets. It is generally resistant to both light and chemicals, though high heat exposure can cause fading in some colored varieties.
Cleaning spinel can be done with ultrasonic and steam cleaners, provided the gemstone is crack-free. Warm soapy water is always a safe and effective method. Store spinel away from other harder gemstones, like diamonds, to prevent scratches.
Despite its hardness, spinel should still be handled with care, especially if the gem has been cut into a delicate shape such as an emerald cut or a complex design.
Sardonyx
Sardonyx is known for its hardness and durability, with a rating of 6.5–7 on the Mohs scale. It is ideal for carved jewelry, such as cameos, pendants, and intaglios. However, it is more difficult to clean due to its porous and banded nature.
Sardonyx should be cleaned with a soft cloth or brush and warm soapy water. Avoid using ultrasonic or steam cleaners, as the vibrations and heat may cause damage to the layered structure of the stone.
To prevent overexposure, limit its time in direct sunlight or high heat environments. Store sardonyx separately to avoid scratches from other stones, and polish it occasionally to maintain its appearance, especially if it is used frequently.
Conclusion
The birthstone of August, represented by peridot, spinel, and sardonyx, embodies a rich tapestry of cultural significance and geological wonder. These gemstones have been cherished across civilizations for their beauty, symbolism, and protective qualities. Whether admired for its cosmic origin, its fiery brilliance, or its layered elegance, each gemstone offers a unique story and meaning.
Peridot, with its single, bright green hue, is a rare gemstone that stands out in the world of birthstones, while spinel captivates with its vast color palette and regal history. Sardonyx, the oldest and most historically entrenched of the August gemstones, brings a timeless charm and symbolism.
For gemstone enthusiasts, jewelry buyers, and those studying gemology, understanding the properties and stories of these August birthstones enhances not only appreciation for the stones themselves, but also for the traditions and histories they represent.