The final month of the year is uniquely distinguished in the world of gemology by its association with not one, but three distinct and celebrated birthstones: turquoise, zircon, and tanzanite. This multiplicity offers individuals born in December a rich palette of choices, from the ancient, sky-blue allure of turquoise to the brilliant fire of zircon and the modern, velvety blue-violet of tanzanite. Each stone carries its own unique history, geological origin, and set of properties, yet all are united under the umbrella of December's celebratory spirit. As the year draws to a close and many cultures observe festivals of light and renewal—from the Winter Solstice to Hanukkah and Christmas—these gemstones serve as fitting symbols of clarity, wisdom, and good fortune. This comprehensive guide will explore the profound history, geological formation, gemological characteristics, and cultural significance of these three remarkable gems, providing an expert overview for collectors, jewelry buyers, and gemology enthusiasts.
History and Lore: A Journey Through Time
The story of December's birthstones is a tale of three distinct gems, each with a history that reflects the eras in which they rose to prominence. The most ancient of these is undoubtedly turquoise, a stone that has been cherished for millennia across numerous civilizations.
The Ancient Legacy of Turquoise
Turquoise stands as the traditional and most historically significant birthstone for December. Its name derives from the French phrase pierre tourques, or "Turkish stone," a reference to the trade routes through which the gem was brought to Europe from Persia. Long before its arrival in the West, ancient civilizations revered this sky-blue mineral. Sources of turquoise extend from the ancient mines of Persia (modern-day Iran) to the Sinai Peninsula, where it was mined by the ancient Egyptians as early as 6000 BCE. Pharaohs and priests adorned themselves with turquoise amulets, believing the stone offered protection and a connection to the divine.
In more recent history, turquoise gained immense cultural significance among Native American tribes of the American Southwest. For peoples such as the Navajo, Zuni, and Pueblo, turquoise is not merely an ornamental stone but a sacred element of their cosmology, representing the sky and water—essential elements for life in an arid landscape. It is considered a symbol of good fortune and success, a belief that has persisted through centuries. This deep-rooted historical context makes turquoise a gem of profound cultural weight, connecting the wearer to a lineage of human history that spans continents and epochs.
The Modern Triumvirate: Zircon and Tanzanite
While turquoise holds the title of traditional birthstone, the modern list of December birthstones was expanded to include zircon and, more recently, tanzanite. This expansion reflects both the evolving nature of the jewelry market and the discovery of new and compelling gemstones.
Zircon, not to be confused with the synthetic cubic zirconia, is one of the oldest minerals on Earth, with deposits dating back billions of years. For centuries, the fiery, colorless variety of zircon was a popular diamond simulant, prized for its high refractive index and exceptional brilliance. However, zircon occurs in a spectrum of colors, with the warm, earthy tones of brown and the vibrant blue of heat-treated stones being particularly notable. Its inclusion as a December birthstone provides an alternative with a classic, brilliant appearance and a geological history that is truly ancient.
The newest addition to the December birthstone family is tanzanite. Discovered in the Merelani Hills of Tanzania in the mid-20th century, this gemstone is a relative newcomer to the gemological world. Its discovery is a modern tale, and its rapid ascent to prominence was fueled by its unique color and a major marketing campaign by Tiffany & Co., which introduced the stone to the world in 1968 and hailed it as "the most beautiful blue gemstone discovered in over 2,000 years." Tanzanite's singular, saturated hue—ranging from ultramarine to violet—set it apart from all other blue gemstones and secured its place as a modern classic.
Geological Formation and Global Sources
The origins of these three gems are as diverse as their appearances, with each forming under unique geological conditions in specific locations around the globe.
Turquoise: A Hydrous Copper Mineral
Turquoise is a secondary mineral that forms when acidic, copper-rich waters percolate through existing rock formations containing aluminum and phosphorus. This process occurs over millions of years in arid or semi-arid climates, where the evaporation of water concentrates the minerals into veins and nodules. The most famous sources for high-quality turquoise are located in Iran (Persia), which produces the classic, uniform robin's-egg blue stones, and the Southwestern United States (Arizona, New Mexico, Nevada), where mines such as the Sleeping Beauty, Kingman, and Turquoise Mountain produce a wide variety of colors and matrix patterns. Other significant sources include Egypt, China, and Afghanistan. The color of turquoise is directly influenced by its copper content (producing blue hues) and iron content (producing greenish tones), while the matrix—the host rock remnants—creates unique, web-like patterns prized by connoisseurs.
Zircon: A Detrital Zirconium Silicate
Zircon is a mineral belonging to the group of zirconium silicates. It is highly resistant to weathering and is often found in placer deposits—sands and gravels that have been transported by water from their original source rock. This durability means that zircon crystals can be billions of years old, making them invaluable to geologists for dating the Earth's crust. While zircon is found in many parts of the world, including Australia, Sri Lanka, and Thailand, the most prized blue zircon typically originates from Cambodia and Vietnam. The vivid blue color seen in most jewelry is almost always the result of heat treatment, which transforms naturally occurring brown zircon into the desirable cool blue shade. This process is a standard and accepted practice in the gem trade, and the resulting blue zircon is celebrated for its exceptional brilliance and fire.
Tanzanite: A Unique Geologic Anomaly
Tanzanite's origin story is one of geological serendipity. It is a variety of the mineral zoisite and is found in only one location on the planet: a small, four-square-kilometer mining area in the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. The gem formed under an extremely specific and rare set of geological conditions involving the contact metamorphism of limestone by igneous intrusions, which introduced the necessary elements (calcium, aluminum, silicon, and trace amounts of vanadium and chromium) for zoisite to form. The intense heat and pressure from these geological events caused the vanadium-bearing zoisite to transform into the rich blue-violet crystals we know as tanzanite. Due to its singular source, tanzanite is considered a "generation gemstone," with geologists estimating that the current deposits may be exhausted within a few decades, adding to its allure and value.
Gemological Properties
Understanding the physical and optical properties of a gemstone is crucial for both identification and care. The three December birthstones possess distinct characteristics that define their appearance and durability.
A Comparative Overview
The following table summarizes the key gemological properties of turquoise, zircon, and tanzanite, providing a clear comparison for enthusiasts and buyers.
| Property | Turquoise | Zircon (Blue) | Tanzanite |
|---|---|---|---|
| Chemical Composition | Hydrated copper aluminum phosphate (CuAl₆(PO₄)₄(OH)₈·4H₂O) | Zirconium silicate (ZrSiO₄) | Calcium aluminum hydroxyl sorosilicate (Ca₂Al₃(SiO₄)₃(OH)) |
| Crystal System | Triclinic | Tetragonal | Orthorhombic |
| Mohs Hardness | 5 - 6 | 6.5 - 7.5 | 6.5 - 7 |
| Refractive Index | 1.610 - 1.650 | 1.925 - 2.015 | 1.691 - 1.700 |
| Key Characteristics | Opaque, waxy luster, often contains a matrix (webbing or spots) | High brilliance and fire, often heat-treated for color | Strong trichroic (pleochroic) showing blue, violet, and reddish tones |
Detailed Analysis
Turquoise: As an opaque gem, turquoise is valued for its rich, even color rather than its brilliance. Its hardness on the Mohs scale (5-6) makes it relatively soft compared to many other gemstones, meaning it can be scratched or abraded with rough handling. It is also porous and can be susceptible to discoloration from chemicals, lotions, and even the oils in human skin. Consequently, turquoise is often stabilized (treated with a clear resin) in the gem trade to enhance its durability and color retention.
Zircon: Zircon is one of the most brilliant of all natural gemstones, a property due to its high refractive index, which is even greater than that of a diamond. This exceptional brilliance, combined with strong dispersive properties (the ability to split light into its spectral colors), gives blue zircon a fiery sparkle that is highly sought after. With a Mohs hardness of 6.5 to 7.5, it is reasonably durable for most jewelry applications, though it can be brittle and susceptible to chipping if struck with force due to its tetragonal crystal structure.
Tanzanite: Prized for its mesmerizing and unique color, tanzanite exhibits strong pleochroism—the phenomenon of showing different colors when viewed from different crystal directions. A cut tanzanite gem will typically display a dominant blue, a secondary violet, and a tertiary reddish hue depending on the orientation. With a Mohs hardness of 6.5 to 7, it is similar in durability to zircon but requires more care than harder stones like sapphire. Its relatively recent discovery means that traditional cutting styles are still being perfected, with modern cuts designed to maximize its captivating color.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, all three December birthstones are imbued with rich symbolism and are believed by many to possess metaphysical properties.
Turquoise: The Master Healer
For centuries, turquoise has been regarded as a stone of protection, wisdom, and good fortune. It is widely considered a "master healer" in metaphysical circles, believed to align all the chakras, ground and stabilize the wearer, and absorb negative energies. Its connection to the sky and water has made it a symbol of tranquility, peace, and spiritual grounding. Historically, it was worn by warriors and travelers as a powerful amulet against harm and was thought to change color to warn its owner of impending danger or illness.
Zircon: The Stone of Virtue
Blue zircon is traditionally associated with wisdom, honor, and purity. It is believed to promote spiritual growth and provide a sense of clarity and peace to the wearer. In the Middle Ages, zircon was thought to induce sound sleep, ward off evil spirits, and bring prosperity and honor. Its brilliant light was seen as a metaphor for enlightenment and truth, making it a powerful stone for those seeking to deepen their understanding of themselves and the world around them.
Tanzanite: The Stone of Transformation
As a relatively new gem, tanzanite has quickly developed its own lore. It is often called the "stone of transformation" and is believed to facilitate a higher consciousness, intuition, and spiritual perception. Metaphysical practitioners associate tanzanite with the throat and third-eye chakras, believing it aids in clear communication and psychic abilities. Its unique energy is said to help the wearer move from one stage of life to another with grace and understanding, making it a powerful gem for those undergoing significant life changes.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any piece of jewelry. Due to their differing physical properties, the three December birthstones require specific maintenance routines.
Turquoise: Given its relative softness and porosity, turquoise requires the gentlest care. It should be cleaned with a soft, dry cloth. Avoid using any chemicals, including household cleaners, soaps, or even lotions and perfumes, as these can damage the stone's surface or cause discoloration over time. It is best to store turquoise jewelry separately to prevent it from being scratched by harder stones.
Zircon: While harder than turquoise, zircon can be brittle. It is susceptible to chipping and should be handled with care to avoid hard impacts. To clean zircon, use warm water, a mild soap, and a soft brush. Ultrasonic and steam cleaners are generally not recommended, as the stone's natural inclusions or treatments could be affected by the heat and vibrations.
Tanzanite: Due to its popularity and good hardness, tanzanite is often set in rings and bracelets, but care should still be taken. It is generally safe to clean tanzanite with warm, soapy water and a soft brush. As with zircon, it is advisable to avoid ultrasonic cleaners and high heat, which could potentially alter the stone's color or cause damage. Given its rarity and value, it is wise to remove tanzanite jewelry before engaging in activities that could expose it to hard knocks or chemicals.
Conclusion
The birthstones of December—turquoise, zircon, and tanzanite—offer a remarkable trifecta of history, science, and symbolism. Turquoise provides a direct link to the ancient world, a talisman of protection and good fortune that has been cherished for millennia. Zircon brings a touch of classic brilliance and fiery sparkle, a mineral as old as the Earth itself, holding the wisdom of ages. And tanzanite represents the thrill of modern discovery, a singular gem born of a unique geological event, capturing the deep, transformative blues of twilight. Together, they form a compelling and diverse group, perfectly suited to the final month of the year—a time of reflection, celebration, and the promise of a new beginning. For anyone born in December, the choice between these three gems is not merely an aesthetic one; it is an opportunity to connect with a rich tapestry of human history, geological wonder, and personal meaning.