The month of December is uniquely distinguished in the gemological calendar by its association with not one, but three principal birthstones: the ancient and opaque Turquoise, the newly discovered and pleochroic Tanzanite, and the brilliant and versatile Zircon. This multiplicity offers those born in the year's final month a remarkable spectrum of color, history, and symbolism, from the sky-blue treasures of antiquity to the vibrant violet-blue of modern discovery. While the tradition of birthstones has evolved over millennia, December’s collection stands out as a testament to both enduring legacy and contemporary appeal.
This guide provides a comprehensive exploration of these three gems, delving into their distinct histories, geological origins, and gemological properties. We will trace the journey of each stone from its formation deep within the earth to its place in jewelry and lore. The article will cover the rich historical and cultural significance of these gems, examine the scientific principles that define their beauty and durability, and offer practical advice for their care. For the enthusiast, the collector, or the prospective buyer, understanding the unique characteristics of Turquoise, Tanzanite, and Zircon is key to appreciating their full value and significance.
History and Lore: A Journey Through Time
The tradition of assigning specific gemstones to birth months has ancient roots, with some sources tracing its origins to Mesopotamia and later being adopted by the Greeks and Romans. Early birthstone lists, often inspired by biblical descriptions of the High Priest's breastplate, designated a single stone for each month. For December, the earliest lists were inconsistent, with some identifying Ruby as the stone for the month's birth. However, the modern collection of December birthstones reflects a long and evolving history, culminating in the current trio.
Turquoise: The Ancient Talisman
Turquoise stands as the oldest and most traditional of the December birthstones, with a history of human admiration stretching back thousands of years. It was the first gemstone officially recognized as a December birthstone in modern times. Its journey into the birthstone list began in 1870 when Tiffany & Co. published its "Gregorian Birthstone Poems" pamphlet, which listed Turquoise as the stone for December. This was formalized in 1912 by the National Association of Jewellers (now the Jewellers of America), which established Turquoise as the primary birthstone, with Lapis Lazuli as an alternative. Turquoise has remained a cornerstone of December's identity ever since.
Culturally, Turquoise has been a universal symbol of protection, good fortune, and wisdom. Its use in adornment is found across ancient civilizations, from the Egyptians to the Persians and Native American peoples. Persian Turquoise, in particular, is historically significant. Sourced from ancient mines in Iran, it is celebrated for its vivid, evenly saturated sky-blue color and is prized for its purity and remarkable hue, often with minimal to no matrix (the dark veining sometimes seen in the stone). Another historically significant variety is Sleeping Beauty Turquoise, named for the mountain in Arizona from which it was mined. This variety is renowned for its pure, robin's-egg blue color and exceptionally low matrix, making it highly sought after for its smooth, uniform appearance.
Tanzanite: The Modern Marvel
In stark contrast to Turquoise's ancient lineage, Tanzanite is a distinctly modern addition to the birthstone family. It is the newest member of the December trio, officially added to the list in 2002 by the Jewellers of America. Its discovery is a recent and dramatic story. Sources indicate that this rare gem is found exclusively in a very small area of Northern Tanzania, a mining region that is the only known source in the world. This extreme geographic limitation contributes significantly to its rarity and value.
Tanzanite's rapid ascent to birthstone status was driven by its unique beauty and a concerted marketing effort. Its rich violet-blue color, which exhibits pleochroism (showing different colors like blue and violet when viewed from different angles), captivated the jewelry world. The addition of Tanzanite to the official list reflects the dynamic nature of the birthstone tradition, showing its capacity to incorporate new and significant gemological discoveries for a modern audience.
Zircon: The Sparkling Enigma
Zircon, the third of the modern December birthstones, has a history that is both long and frequently misunderstood. It was added to the 1912 list in 1952 by the Jewelry Industry Council of America, solidifying its place alongside Turquoise. For centuries, Zircon has been prized for its exceptional brilliance and fire, which rival that of diamond. It is one of the oldest minerals on Earth, providing valuable information to geologists about the age of rocks.
A common point of confusion is the difference between Zircon and the man-made cubic zirconia (CZ). Zircon is a natural gemstone, while CZ is a synthetic diamond simulant. This confusion can unfortunately detract from Zircon's reputation as a fine gem. Among its various colors, which range from colorless to yellow-gold and brownish-red, the blue variety is most closely associated with December. Blue Zircon, often achieved through heat treatment of brown zircon, is celebrated for its sparkling clarity and cool, icy hue, making it a popular and durable alternative for those born in the month.
Geological Formation and Global Sources
The three December birthstones originate from vastly different geological processes and are mined in distinct regions of the world, contributing to their unique characteristics and rarity.
Turquoise: An Hydrous Phosphate Mineral
Turquoise is not a crystalline gem but a hydrous phosphate of copper and aluminum. It forms in arid regions where acidic, copper-rich water seeps through aluminum-bearing rocks, such as feldspar-rich porphyry. Over millions of years, this process creates nodules and veins of the turquoise mineral, often in association with a host rock matrix.
Significant sources for high-quality Turquoise are concentrated in the Southwestern United States and Iran. The Sleeping Beauty Mine in Arizona was a historically important source for the pure, sky-blue material that bears its name. Other notable U.S. sources include mines in Nevada, New Mexico, and Colorado. Persian Turquoise from Iran is considered the benchmark for quality, prized for its distinctive and highly desirable sky-blue color. While other sources exist globally, the finest material is consistently associated with these classic localities.
Tanzanite: A Unique Geological Anomaly
Tanzanite's formation story is as unique as its color. It is a variety of the mineral zoisite and owes its violet-blue hue to trace amounts of vanadium. Its geological setting is extraordinarily rare. The gem is found in a small, four-square-kilometer mining area in the Merelani Hills of Northern Tanzania. The specific geological conditions required for its formation—a unique combination of heat, pressure, and specific mineralizing fluids acting on the host rock—are believed to be the result of a tectonic event that occurred roughly 585 million years ago. This localized and singular origin makes Tanzanite one of the most geographically restricted gemstones of commercial importance, a fact that underscores its rarity.
Zircon: A High-Temperature Silicate Mineral
Zircon is a zirconium silicate (ZrSiO₄) that forms in igneous and metamorphic rocks. It is one of the oldest minerals on Earth, often found as detrital grains in sedimentary deposits. High-quality gem Zircon is typically sourced from placer deposits, where it has been eroded from its original host rock and concentrated by water action.
Major sources for gem-grade Zircon include Thailand, Cambodia, Sri Lanka, and Australia. The blue variety, most relevant to December, is often produced by heat-treating brownish Zircon from these locations. The process involves heating the stone to very high temperatures (approaching 1,000°C) in a controlled environment, which removes the brown color-causing elements and results in a stable and brilliant blue.
Gemological Properties: A Scientific Comparison
Understanding the physical and chemical properties of these gems is essential for appreciating their unique characteristics, durability, and value. The following table provides a direct comparison of the key gemological data for Turquoise, Tanzanite, and Zircon, based on information derived from the provided sources.
| Property | Turquoise | Tanzanite | Zircon |
|---|---|---|---|
| Chemical Composition | Hydrous phosphate of copper and aluminum | Calcium aluminum hydroxyl sorosilicate (Zoisite variety) | Zirconium silicate (ZrSiO₄) |
| Hardness (Mohs Scale) | 5 - 6 | 6.5 - 7 | 6.5 - 7.5 |
| Crystal System | Triclinic (massive, no distinct crystals) | Orthorhombic | Tetragonal |
| Refractive Index | N/A (opaque) | 1.690 - 1.700 | 1.920 - 1.980 |
| Color | Sky-blue to greenish-blue, often with matrix | Rich violet-blue, pleochroic (blue/violet) | Colorless, yellow-gold, brown, blue (heat-treated) |
| Transparency | Semi-transparent to opaque | Transparent to translucent | Transparent |
Hardness and Durability
Hardness, measured on the Mohs scale, is a critical factor for a gemstone's suitability for jewelry, particularly for rings worn daily.
- Turquoise is the softest of the three, with a hardness of 5 to 6. This makes it susceptible to scratching and damage from chemicals, lotions, and even skin acids. It requires careful handling and is often set in protective settings or used in pieces that receive less wear, like pendants and earrings.
- Tanzanite has a hardness of 6.5 to 7, making it moderately durable. However, it has poor toughness due to perfect cleavage in one direction. This means a sharp blow can cause the stone to split along a cleavage plane. Consequently, Tanzanite is considered fragile and is best set in protective settings for jewelry that won't be subjected to hard knocks.
- Zircon is the hardest and most durable of the trio, with a hardness of 6.5 to 7.5 and good toughness. Its high refractive index gives it exceptional brilliance and fire, making it an excellent choice for all types of jewelry, including rings. However, like Tanzanite, some Zircon can be brittle due to cleavage.
Color and Clarity
The visual appeal of these stones is defined by their distinct color and clarity characteristics.
- Turquoise is prized for its unique sky-blue to greenish-blue hues. Its opacity is typical, and many stones feature a characteristic dark or brownish veining known as "matrix." The most valuable varieties, like Persian and Sleeping Beauty Turquoise, are prized for their vibrant, even color and minimal matrix.
- Tanzanite is celebrated for its rich, saturated violet-blue color. A key gemological feature is its strong pleochroism, where a single stone can display different colors (typically blue and violet) when viewed from different angles. This property is a key identifier for the gem.
- Zircon is most famous in its blue form for December, which exhibits a brilliant, clear blue color and a sparkle that can be mistaken for diamond. It is known for its high clarity, with most gem-quality stones being "eye-clean."
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, all three December birthstones are rich in symbolism and have been attributed with various metaphysical properties throughout history.
- Turquoise is widely regarded as a stone of protection, wisdom, and good fortune. It has been worn as a talisman to ward off negative energy and bring peace to the wearer. Its calming blue and green hues are associated with tranquility and emotional balance.
- Tanzanite, as a modern gem, has developed a lore centered on transformation and spiritual awakening. It is said to foster compassion, calmness, and a higher consciousness, making it a stone for those seeking new beginnings and deeper understanding.
- Zircon is associated with clarity, wisdom, and a sense of balance. It is believed to promote restful sleep and has been historically used to attract wealth and prosperity. The colorless variety, in particular, is linked to purity and spiritual enlightenment.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gems, with cleaning methods varying significantly based on their durability and treatment.
- Turquoise is porous and sensitive. It should never be cleaned with ultrasonic cleaners, steam, or harsh chemicals. The safest method is to wipe it with a soft, dry cloth. If needed, use lukewarm water with a tiny amount of mild soap, rinse quickly, and dry immediately. It should be protected from cosmetics, lotions, and excessive heat.
- Tanzanite is sensitive to heat and pressure. It should be cleaned with warm, soapy water and a soft brush. Ultrasonic and steam cleaners are not recommended. Due to its cleavage and fragility, it should be stored carefully to avoid scratches and impacts.
- Zircon is generally durable but can be brittle. It is safe to use warm, soapy water and a soft brush for cleaning. While it can withstand an ultrasonic cleaner, steam cleaning is not recommended due to the potential for thermal shock, especially in stones that have been heat-treated.
Conclusion
The birthstones of December—Turquoise, Tanzanite, and Zircon—offer a compelling triad of gems, each with a unique narrative and set of attributes. Turquoise connects us to an ancient past, a talisman of protection revered for millennia. Tanzanite represents the thrill of modern discovery, a rare gem from a single corner of the world whose vibrant color captures the imagination. Zircon provides a bridge between past and present, a brilliant and durable stone that rivals diamond in its fire and has been cherished for its beauty for centuries. Together, they provide a rich palette of blue hues and a diverse range of choices for those born in the final month of the year, ensuring a perfect match for every personal style and preference.