Introduction
As one of the traditional birthstones for the month of December, turquoise stands as a gemstone of remarkable historical depth and distinctive aesthetic. Distinguished by its opaque texture and a captivating color spectrum ranging from sky blue to verdant green, turquoise has been a fixture in human adornment for millennia. Its significance extends far beyond mere decoration; it has served as a talisman of protection, a symbol of status, and a subject of geological fascination. This article explores the multifaceted nature of the turquoise birthstone, drawing upon its rich history across ancient civilizations, detailing its unique geological formation, and examining the gemological properties that define it. By synthesizing information regarding its cultural symbolism, primary sources, and practical care, we present a comprehensive overview of this enduring gem.
History and Lore
The history of turquoise is as varied as its hues, with documentation of its use spanning continents and epochs. In the ancient world, turquoise was not merely a decorative stone but an object of profound spiritual and royal importance. In Egypt, it was revered as a symbol of life and divine protection. Historical records highlight its prominence in royal contexts, most notably through the funerary mask of King Tutankhamun, who ruled Egypt over 3,000 years ago. The intricate inlays of turquoise in this artifact underscore the stone's vital role in religious ceremonies and the afterlife.
In the East, turquoise held equally high esteem. Ancient Chinese artisans, who prized the stone over 3,000 years ago, carved it into intricate forms for both decorative and ceremonial use. The stone was associated with the heavens and the gods, believed to bring good fortune to the wearer. Similarly, in the Nishapur district of Iran, turquoise has been mined for more than a millennium. The Persians developed a deep appreciation for the stone, particularly favoring the intense, even-colored blue varieties. The term "Persian turquoise" has become a color grade descriptor in the modern trade, applied to stones of that specific hue regardless of their geographical origin, a testament to the high standard set by this ancient source.
The journey of turquoise to Europe is reflected in its etymology. The name is derived from the French pierre turquois, meaning "Turkish stone," as the gem was initially brought to the continent through Turkey. In European tradition, the stone acquired romantic and superstitious meanings; the gift of a turquoise ring was traditionally interpreted as a pledge of "forget me not." It was also believed that seeing a turquoise after beholding the new moon would ensure fantastic wealth, according to Hindu mystics.
In the New World, turquoise holds a central place in the cultural heritage of Native American tribes. The Apache believed the stone could be found by following a rainbow to its end, while the Pueblo attributed the gem's color to the sky. The Hopi offered a unique geological interpretation, believing the gem was produced by lizards scurrying over the earth. Beyond folklore, turquoise played a practical role in the lives of these peoples; the Apache believed that attaching the stone to a bow or firearm made one’s aim more accurate. In Tibet, turquoise is considered a national treasure, believed to grant health, good fortune, and protection from evil, while imparting peace to those who wear it. Today, turquoise is recognized not only as a birthstone but also as the gem representing the 11th wedding anniversary.
Geological Formation and Sources
Turquoise is a hydrous phosphate of copper and aluminum, with a chemical composition often represented as CuO·3Al₂O₃·2P₂O₅·9H₂O. It is an secondary mineral that forms in arid regions through a unique geological process. Turquoise deposits are created when copper-rich groundwater seeps through rocks containing aluminum and phosphorus over millions of years. As the water evaporates or cools, it leaves behind precious deposits of the turquoise mineral.
While turquoise occurs worldwide, specific regions have become synonymous with the production of high-quality stones. The southwestern United States is a historically significant source. Although New Mexico was the largest producer until the 1920s, today most U.S. production comes from Arizona and Nevada. Mines in these states bear evocative names such as Dry Creek, Easter Blue, and Fox. The Kingman mine in Arizona is noted as a historically important source known for producing intense blue turquoise. Another significant Arizona mine, the Sleeping Beauty mine, was a prolific producer for over four decades before closing to turquoise mining.
The Nishapur district in Iran remains a legendary source, having been mined for over 1,000 years. The "robin's egg blue" or "sky blue" stones from this region set the global standard for color and quality. In the modern market, China is the world's largest producer of turquoise, with the Hubei Province in central China being the source of most gem-quality turquoise currently mined. Mexico is also a notable producer of the gem.
Gemological Properties
Turquoise is defined by a specific set of physical characteristics that distinguish it from other blue and green gemstones. Its most prominent feature is its opacity; unlike many gemstones that are valued for transparency and brilliance, turquoise is prized for its solid, even color.
Color and Appearance The color range of turquoise is vast, spanning from a pure sky blue to a distinct apple green. The blue hues are derived from copper, while the greenish tints are caused by iron impurities in the chemical structure. The most desirable color is a uniform, intense blue, often described as "robin's egg blue." Many varieties of turquoise exhibit a "matrix," which is a remnant of the host rock in which the stone formed, appearing as a brown, black, or yellowish webbing or patch within the blue stone.
Hardness and Durability On the Mohs scale of hardness, turquoise ranks between 5 and 6. This relatively low hardness makes the stone softer than quartz and much softer than corundum (sapphire and ruby). Consequently, turquoise is susceptible to scratching and abrasion. However, this same softness makes it easier to carve and shape into intricate designs, a quality that has been exploited by artisans throughout history.
Treatments and Enhancements Due to its porous nature and relatively soft texture, turquoise is frequently treated to improve its durability and appearance. Treatments include dyeing to enhance or standardize color, and the addition of an epoxy or acrylic resin to increase hardness and stabilize the stone. Some stones are also treated with a metal-loaded epoxy to fill cavities and imitate pyrite inclusions, creating a "spiderweb" effect. These treatments are standard in the industry but must be considered when evaluating the stone's value and care requirements.
Summary of Key Gemological Properties
| Property | Description |
|---|---|
| Chemical Composition | Hydrous phosphate of copper and aluminum (CuO·3Al₂O₃·2P₂O₅·9H₂O) |
| Color | Sky blue to apple green; often contains a brown or black matrix |
| Luster | Waxy to subvitreous (porcelain-like) |
| Hardness (Mohs) | 5 - 6 |
| Transparency | Opaque |
| Crystal System | Triclinic |
| Treatments | Dyeing, impregnation with epoxy or acrylic resin, stabilization |
Symbolism and Metaphysical Beliefs
Across cultures, turquoise has been imbued with powerful symbolic meaning, often centering on protection, health, and spiritual well-being. In ancient Egypt, it was seen as a conduit for divine protection, shielding the wearer from harm. This belief in its protective power is echoed in Tibetan culture, where turquoise is a national treasure believed to ward off evil and grant good fortune.
The stone's connection to the sky and heavens is a recurring theme. The Pueblo belief that the gem's color came from the sky highlights this celestial association. For the Apache, the stone was linked to the rainbow, a symbol of hope and promise. The belief that turquoise could improve aim when attached to a weapon suggests a metaphysical connection to skill and precision.
In more modern interpretations, turquoise is said to impart peace and tranquility. It is often associated with emotional balance and the calming of stress. The European tradition of the turquoise ring signifying "forget me not" links the stone to enduring love and memory. These diverse beliefs, ranging from practical aids in hunting to spiritual shields against evil, demonstrate the deep and varied symbolic weight turquoise has carried through history.
Care and Cleaning
The gemological properties of turquoise dictate specific care requirements to ensure its longevity. With a hardness of only 5 to 6 and a porous structure, turquoise is vulnerable to damage from physical impact, chemicals, and heat.
Vulnerabilities * Heat: High heat can cause turquoise to crack or lose its color. It should never be subjected to steam cleaning or high-temperature jewelry repair processes. * Chemicals: Acids can damage the stone. Furthermore, turquoise can be discolored by common substances such as cosmetics, skin oils, perspiration, and even some lotions. The treated surfaces of some turquoise are particularly susceptible to damage from heat or solvents. * Scratching: Due to its moderate hardness, turquoise should be stored separately from harder gemstones and metals to prevent scratching.
Cleaning Recommendations The safest method for cleaning turquoise jewelry is with warm, soapy water and a soft brush or cloth. It is imperative to avoid ultrasonic cleaners and steam cleaners, as these can cause significant damage. After cleaning, the piece should be dried thoroughly. To maintain the stone's luster and prevent discoloration, it is advisable to wipe turquoise jewelry with a soft, damp cloth regularly to remove oils and dirt.
Conclusion
Turquoise remains a gemstone of profound significance, bridging the gap between ancient history and contemporary style. Its journey from the arid mines of Iran, China, and the American Southwest to the adornments of pharaohs, royalty, and modern individuals is a testament to its enduring appeal. Defined by its opaque, sky-blue to green body color and a hardness of 5 to 6 on the Mohs scale, turquoise is a gem that requires appreciation for its unique character and care requirements. Whether valued for its historical role as a protective talisman in Egypt and Tibet, its symbolic connection to the sky and good fortune in Native American cultures, or its status as a traditional December birthstone, turquoise continues to captivate. Its rich legacy, geological uniqueness, and vibrant symbolism ensure its place as a cherished and timeless gemstone.