Turquoise is a captivating gemstone, renowned for its distinctive blue-to-green hues and a rich history spanning millennia. As the traditional birthstone for December, it holds a significant place in both cultural lore and the world of gemology. This article delves into the origins, properties, historical significance, and care of this remarkable gem, drawing solely from available sources.
History and Lore
The history of turquoise is deeply interwoven with human civilization. Evidence suggests its use dates back thousands of years, with examples found in ancient Egypt, adorning the funerary mask of King Tut, who ruled over 3,000 years ago. The gem held considerable importance for Native American cultures, particularly the Apache, who believed following a rainbow would lead to its discovery and that attaching it to weaponry would improve accuracy. Different tribes attributed unique origins to the stone; the Pueblo believed turquoise derived its color from the sky, while the Hopi associated it with lizards scurrying across the earth.
In European traditions, turquoise symbolized forgetfulness, with a turquoise ring signifying a promise to “forget me not.” Within Tibetan culture, turquoise is considered a national treasure, believed to bestow health, good fortune, and protection against evil, also imparting peace to the wearer. The gem’s enduring appeal is further evidenced by its presence in the jewelry of Wallis Simpson, the Duchess of Windsor, who owned a notable amethyst and turquoise necklace created by Cartier. It is also traditionally associated with the 11th wedding anniversary.
Geological Formation and Sources
Turquoise is a hydrous phosphate of copper and aluminium, with the chemical formula CuAl6(PO4)4(OH)8·4H2O. Geologists describe it as forming when chemicals seep from surrounding rocks through rainwater and groundwater in semi-humid and dry environments where rock is present. The sky-blue hue is primarily attributed to the presence of copper, while iron contributes to the green coloration.
For over 1,000 years, the Nishapur district of Iran has been a significant source of turquoise. The turquoise originating from this region is highly prized for its even, intense blue color, often described as “robin’s egg blue,” “sky blue,” or “Persian blue.” These terms are now used by trade professionals to denote this specific color, regardless of the stone’s origin. The mother rock in which turquoise is found often remains visible as splotches or a network of veins running through the stone, a pattern sometimes referred to as “spiderweb matrix.” While this veining is valued in the Southwestern United States and Far East, the Near East traditionally prefers unblemished, vein-free material.
Gemological Properties
Turquoise is an opaque mineral, exhibiting colors ranging from its namesake brilliant blue to various shades of green. It typically occurs in massive or nodular formations. Its hardness ranges from 5 to 6 on the Mohs scale, making it relatively soft and susceptible to abrasion.
Here's a table summarizing key gemological properties:
| Property | Value |
|---|---|
| Chemical Formula | CuAl6(PO4)4(OH)8·4H2O |
| Crystal System | Triclinic |
| Color | Blue, Blue-Green, Green |
| Hardness (Mohs) | 5 – 6 |
| Luster | Waxy to Subvitreous |
| Specific Gravity | 2.6 – 2.9 |
| Refractive Index | nα = 1.610, nβ = 1.615, nγ = 1.650 |
| Cleavage | Perfect on {001}, Good on {010} (rarely seen) |
| Diaphaneity | Opaque |
Turquoise exhibits a weak pleochroism, meaning it displays slightly different colors when viewed from different angles. It is fusible in heated hydrochloric and hydrofluoric acids and soluble in hydrochloric acid. The quality of a turquoise stone is assessed based on the uniformity of its color, the quality of its polish, and the symmetry of its cut. Calibrated stones, adhering to standard jewelry setting measurements, are often more desirable. Unlike many gems valued by weight, turquoise is typically sold based on its physical size in millimeters.
Symbolism and Metaphysical Beliefs
Throughout history, turquoise has been imbued with symbolic meaning. Beyond its association with forgetfulness in European traditions and protection in Tibetan culture, the gem is generally believed to impart peace and good fortune to those who wear it. Native American cultures held particularly strong beliefs regarding its power, linking it to accuracy in hunting and a connection to the natural world.
Care and Cleaning
Due to its relatively low hardness, turquoise requires careful handling and maintenance. It is resistant to the effects of normal heat, light, and common chemicals, but can crack if exposed to very high temperatures or sudden temperature changes. It is also prone to abrasion.
Cleaning turquoise is best achieved with warm, soapy water. Ultrasonic and steam cleaners are not recommended, as they can damage the stone. For optimal longevity, turquoise is best set in earrings or pendants, minimizing the risk of impact and abrasion. While not ideal for daily wear in a ring, it can be worn as a special-occasion jewel with a protective mounting and diligent care. The gem can be attacked by hydrochloric and hydrofluoric acids, so exposure to these substances should be avoided.
Conclusion
Turquoise remains a highly valued gemstone, celebrated for its captivating color, rich history, and enduring cultural significance. From its ancient origins in Egypt and the traditions of Native American tribes to its place in European lore and modern jewelry, turquoise continues to fascinate and inspire. Its unique geological formation, combined with its relatively soft nature, necessitates careful handling and appreciation. As a December birthstone, and a gem steeped in symbolism, turquoise offers a tangible connection to the past and a beautiful addition to any collection.