The month of August boasts three recognized birthstones: peridot, sardonyx, and spinel. While peridot and sardonyx have long held the designation, spinel was officially added in 2016 by the American Gem Trade Association (AGTA) and Jewelers of America (JA), acknowledging its historical significance and growing popularity. This article will delve into the history, geological origins, gemological properties, symbolism, and care of spinel, the captivating gemstone increasingly celebrated as an August birthstone.
History and Lore
The story of spinel is intertwined with that of ruby and sapphire. For centuries, before advancements in gemological science allowed for accurate mineral identification, spinel was often mistaken for these more well-known gemstones. In fact, many famous “rubies” adorning historical crown jewels are, upon modern examination, revealed to be spinels. This misidentification led to spinel being revered by royalty and gem enthusiasts alike, though often under a false name. Ancient gemstone merchants prized spinel, referring to it as “balas ruby,” a term used until the late 18th century when the ability to distinguish it as a separate mineral was established.
Sardonyx, one of the older August birthstones, also has a rich history. Its use dates back to ancient times, particularly in Roman civilization, where it was favored for creating seals and signet rings due to its smooth surface and the property of not sticking to hot wax. The banded patterns of sardonyx – alternating layers of brownish-red sard and black or white onyx – were highly valued for carving cameos and intaglios. Both stones were believed to hold protective qualities; Roman soldiers wore sardonyx rings engraved with the image of Mars for courage in battle.
The modern association of specific gemstones with birth months is a relatively recent development. While the concept originates in biblical times with the twelve gemstones on the breastplate of Aaron representing the tribes of Israel, the direct link to birth months emerged between the 16th and 18th centuries. The National Association of Jewelers (now Jewelers of America) formalized a “modern birthstone” list in 1912, and this list has been updated periodically, most recently with the addition of spinel in 2016.
Geological Formation and Sources
Spinel is a magnesium aluminum oxide mineral, formed in metamorphic and igneous rocks. It often occurs alongside other gemstones like ruby and sapphire in marble deposits. The formation process involves high pressure and temperature conditions deep within the Earth’s crust.
Sardonyx, conversely, is a variety of chalcedony, a cryptocrystalline form of silica. It forms through the layering of sard and onyx, creating its distinctive banded appearance. The silica gel, found in cracks within rocks, gradually heats and solidifies, forming the chalcedony layers.
Specific locations for sardonyx are not detailed in the provided sources, but it is noted as being one of the most ancient of the August birthstones. The sources do not provide specific mining locations for spinel, but indicate it has been historically revered and sought after by royalty.
Gemological Properties
Spinel boasts a Mohs hardness of 8, making it a durable gemstone suitable for everyday wear, including in rings. This hardness means it is resistant to scratching and abrasion. It can be safely cleaned using ultrasonic and steam cleaners, although caution is advised if the stone contains fractures. Warm soapy water is always a safe cleaning alternative. Spinel is stable when exposed to light and chemicals, though high heat can cause some colors to fade.
Sardonyx, being a form of chalcedony, has a Mohs hardness of 6.5 to 7.5, making it less durable than spinel.
The following table summarizes the key gemological properties of spinel, as provided in the sources:
| Property | Spinel |
|---|---|
| Mineral | Magnesium Aluminum Oxide |
| Hardness (Mohs) | 8 |
| Stability | Stable to light & chemicals, sensitive to high heat |
| Cleaning | Ultrasonic/Steam (with caution), Warm Soapy Water |
The sources do not provide detailed information on the chemical composition, refractive index, or specific gravity of spinel or sardonyx.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been attributed with various symbolic meanings and metaphysical properties. Sardonyx has been associated with courage, happiness, and clear communication, and was believed to bring stability to marriage and partnerships. Its banded appearance was thought to represent the layers of life and the integration of different energies.
While the sources do not detail specific metaphysical beliefs associated with spinel, its historical association with royalty and its vibrant colors suggest a symbolism of power, grace, and vitality. Opal, another October birthstone, is believed to bring confidence and hope to the wearer.
Care and Cleaning
Due to its hardness of 8, spinel is a relatively durable gemstone. It can be cleaned with ultrasonic and steam cleaners, but caution should be exercised if the stone has any fractures. Warm, soapy water is always a safe and effective cleaning method. Spinel is stable when exposed to light and most chemicals. However, prolonged exposure to high heat can cause some colors to fade.
Sardonyx, with its lower hardness, requires more gentle care. Avoid harsh chemicals and abrasive cleaners. A soft cloth and mild soapy water are recommended for cleaning.
Conclusion
Spinel, alongside peridot and sardonyx, represents the vibrant birthstones of August. While historically often mistaken for ruby and sapphire, spinel has emerged as a gemstone in its own right, celebrated for its durability, beautiful colors, and rich history. The addition of spinel to the modern birthstone list in 2016 reflects a growing appreciation for this captivating gem and provides August-born individuals with a wider range of choices to express their personal style and connect with the symbolism of their birthstone. Sardonyx, with its ancient roots and association with courage and communication, continues to hold a place of honor among the August birthstones.