December is a unique month in the birthstone calendar, offering not one but three official gemstones: turquoise, zircon, and tanzanite. This abundance provides those born in the final month of the year with a diverse palette of cool, wintry blues, from the soft sky tones of turquoise to the vibrant violet-blue of tanzanite and the brilliant clarity of zircon. Each stone carries its own distinct history, geological origin, and set of gemological properties, making the choice of a December birthstone a deeply personal one. This article will delve into the world of these three celebrated gems, exploring their journey from ancient mines to modern jewelry, their scientific characteristics, and the enduring symbolism that has made them cherished for millennia.
The modern list of birthstones, largely standardized in 1912 by the National Association of Jewelers in the United States, draws from a long tradition that traces its roots to the breastplate of Aaron described in the Old Testament. Over centuries, this list has evolved, with December’s selection reflecting a desire to offer variety and choice. Turquoise, with its millennia-long history, represents the traditional choice. Zircon, known for its fire and brilliance, has been associated with December for much of modern history. Tanzanite, a relative newcomer discovered in the 20th century, was added to the official list in 2002, bringing a modern, vivid hue to the December palette. Together, these stones offer a spectrum of options for jewelry enthusiasts, collectors, and those seeking a gem with personal significance.
History and Lore
The history of December’s birthstones is as varied as the gems themselves, spanning ancient civilizations, royal treasuries, and modern discoveries.
Turquoise is arguably the most ancient of the three. Its name is derived from the French pierre turquoise, meaning "Turkish stone," as it was brought to Europe from the mines of Persia (modern-day Iran) through Turkish trade routes. The gemstone has been prized for thousands of years. Ancient Egyptians adorned themselves with turquoise, as evidenced by artifacts from Pharaohs' tombs. It was a favorite of royalty, including the famed Egyptian King Tutankhamun, whose burial mask was inlaid with the stone. The Incas and Mayas of the Americas also held turquoise in high regard, offering it as a sacred gift to their gods. In Tibet, turquoise was so valued that it was used as a form of currency and was considered a birthstone of fortune, health, and success. For Native American tribes of the Southwestern United States, the stone is deeply intertwined with cultural identity, symbolizing youth, strength, and a connection to the earth and sky. Historically, turquoise was believed to be a protective amulet, capable of warning its wearer of impending danger or illness by changing color. It was also a gem of friendship and fidelity, often exchanged between lovers and married couples to preserve their bond.
Zircon’s history is equally storied, though it is often confused with the synthetic cubic zirconia, a common misconception that does a disservice to this natural gem. The name "zircon" may derive from the Arabic zargun, meaning "gold color," a testament to the gem’s warm-hued varieties, though it is most famous for its brilliant blue tones. For centuries, zircon has been associated with wisdom, clarity, and balance. It was believed to promote sound sleep, ward off nightmares, and bring prosperity to its wearer. Its high refractive index and strong dispersion (fire) made it a popular diamond simulant in centuries past, and it was often set in royal jewelry. While not as ancient in its documented use as turquoise, zircon has been a valued gem in European and Asian markets for centuries, appreciated for its durability and dazzling light performance.
Tanzanite is the newest member of the December birthstone family. Its story is a modern geological marvel. The stone was first discovered in 1967 in the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. Local Masai herders initially found the blue crystals, which were soon identified by a prospector named Manuel d’Souza. The gem’s unique violet-blue color, which can range from ultramarine to lavender, was unlike any other known gemstone. Initially, there was skepticism about its natural origin, but it was confirmed to be a variety of the mineral zoisite. The stone was later named "tanzanite" in honor of its country of origin. Its rapid rise to fame was fueled by the jewelry retailer Tiffany & Co., which introduced it to the world in 1968, marketing it as a "gemstone of a generation." Due to its limited geographic source and its captivating color, tanzanite quickly became sought after. In 2002, the American Gem Trade Association (AGTA) added tanzanite to the official list of birthstones for December, recognizing its significance and popularity. Metaphysically, tanzanite is associated with transformation, new beginnings, and heightened intuition, reflecting its relatively recent appearance in the gemological world.
Geological Formation and Sources
The formation and mining locations of these three gems are as distinct as their appearances, each tied to specific geological conditions found in only a few places on Earth.
Turquoise is a hydrous phosphate of copper and aluminum, forming in arid regions where acidic, copper-rich groundwater percolates through pre-existing rocks. Over millennia, this process deposits minerals in cracks and voids, creating the nodular or vein-like formations of turquoise. The gem is almost always found in a matrix, a host rock that can range from a fine, tight structure to a porous, web-like pattern, which significantly affects its durability and appearance. The most significant sources of high-quality turquoise include: * Iran (Persia): Historically the source of the finest, most prized turquoise, known for its even, sky-blue color and minimal matrix. * Southwestern United States: States like Arizona, New Mexico, and Nevada are famous for their turquoise, often characterized by a greenish-blue hue and distinctive matrix patterns. Mines like Kingman, Sleeping Beauty, and Morenci are well-known. * China: A major producer in modern times, offering a wide range of colors and qualities. * Egypt: The source of the ancient Egyptian turquoise, such as that from the Sinai Peninsula. * Other locations: Turquoise is also mined in Mexico, Tibet, and parts of Central Asia and Africa.
Zircon is a zirconium silicate (ZrSiO₄) that forms in igneous and metamorphic rocks. It is one of the oldest minerals on Earth, with some crystals dating back billions of years. Blue zircon, the variety most associated with December, is typically heat-treated from brown zircon to achieve its desirable color. Natural blue zircon is rare. Major sources for zircon include: * Cambodia: Known for producing high-quality, heat-treated blue zircon. * Sri Lanka: A traditional source for zircon of various colors. * Myanmar (Burma): Produces zircon, including some that can be heat-treated to blue. * Australia: A significant source of zircon, though often for industrial use, some gem-quality material is found. * Other locations: Zircon is also mined in Brazil, Nigeria, and Vietnam.
Tanzanite is a variety of the mineral zoisite, containing trace amounts of vanadium that give it its signature blue-violet color. It is found exclusively in the Merelani Hills of Tanzania, in a very small area of just a few square kilometers. The geological conditions for its formation are unique and are believed to be the result of a tectonic shift that occurred between 500 and 600 million years ago. The crystals are found in three main mining blocks (A, B, and C) in the Merelani region. Due to its single-source origin, tanzanite is considered even rarer than diamond. The mining is often small-scale and artisanal, and the supply is finite, which contributes to its value and allure.
Gemological Properties
Understanding the physical and chemical properties of these gems is crucial for both jewelers and consumers, as it informs their durability, care requirements, and value.
The following table summarizes the key gemological properties of turquoise, zircon, and tanzanite, based on data from the provided sources.
| Property | Turquoise | Zircon (Blue) | Tanzanite |
|---|---|---|---|
| Mineral Group | Phosphate | Silicate | Silicate (Zoisite variety) |
| Chemical Formula | Hydrous copper aluminum phosphate | ZrSiO₄ | Ca₂(Al,Fe³⁺)₃(SiO₄)₃(OH) |
| Mohs Hardness | 5 - 6 | 6.5 - 7.5 | 6.5 - 7 |
| Crystal System | Triclinic | Tetragonal | Orthorhombic |
| Refractive Index | 1.61 - 1.65 | 1.92 - 2.01 | 1.69 - 1.70 |
| Specific Gravity | 2.60 - 2.90 | 4.60 - 4.70 | 3.35 |
| Color | Sky blue to greenish-blue | Bright, clear blue (often heat-treated) | Rich violet-blue (pleochroic) |
| Luster | Waxy to subvitreous | Adamantine (brilliant) | Vitreous (glass-like) |
| Transparency | Opaque to translucent | Transparent to translucent | Transparent |
Turquoise is the softest of the three, with a Mohs hardness of 5 to 6. This makes it susceptible to scratching and abrasion. It is often treated to enhance its durability and color. Stabilization, a process where the stone is impregnated with a clear resin, is common and accepted in the industry to reduce porosity and prevent color change. Natural, untreated turquoise is rare and highly valued. Its opacity and unique matrix patterns are key characteristics, and it is often cut en cabochon (a smooth, rounded dome) to showcase its color and texture.
Zircon is one of the hardest natural gemstones, with a Mohs hardness of 6.5 to 7.5, making it quite durable for jewelry. Its most remarkable property is its high refractive index and strong dispersion, which gives it exceptional brilliance and fire, often exceeding that of a diamond. Blue zircon is almost always the result of heat treatment of brown zircon, a standard and permanent practice that is accepted by the gemological community. Natural blue zircon is extremely rare. Zircon is highly transparent and is typically faceted to maximize its light performance.
Tanzanite has a Mohs hardness of 6.5 to 7, making it more durable than turquoise but still requiring careful handling. Its most distinctive gemological property is its strong pleochroism—the ability to show different colors when viewed from different crystal directions. Fine tanzanite displays a trichroic effect, showing blue, violet, and burgundy tones. The gem is almost always heat-treated to achieve its vivid blue-violet color, as most mined tanzanite is brownish. This treatment is stable and permanent. Due to its pleochroism, cutters must orient the crystal carefully to present the most desirable color face-up. It is typically faceted and set in protective jewelry settings to prevent impact.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, December’s birthstones are rich in symbolism and metaphysical lore, offering wearers a connection to ancient traditions and spiritual beliefs.
Turquoise is universally regarded as a stone of protection, healing, and good fortune. Across cultures, it has been used as a talisman to guard against negative energy, accidents, and evil spirits. Its calming blue-green hues evoke feelings of tranquility, peace, and serenity, making it a stone for emotional balance and stress relief. It is also strongly associated with friendship and loyalty, believed to strengthen bonds and promote honest communication. In many traditions, turquoise is linked to the throat chakra, enhancing self-expression and creativity. For those seeking wisdom and spiritual grounding, turquoise is said to connect the wearer to the earth and sky, fostering a sense of wholeness.
Zircon is celebrated for its connection to wisdom, clarity, and honor. It is believed to sharpen mental focus, enhance concentration, and promote clear thinking. Metaphysically, zircon is associated with spiritual growth and enlightenment, helping to align the physical and spiritual selves. It is also thought to bring prosperity and honor to its wearer, making it a popular gem for those seeking success in their endeavors. Some traditions hold that zircon can aid in restful sleep and ward off nightmares, acting as a protective stone during the night. Its brilliant fire is seen as a symbol of inner light and clarity of purpose.
Tanzanite, as a modern gem, has quickly developed its own set of metaphysical associations, often tied to its unique color and origin. It is primarily linked to transformation, intuition, and spiritual awakening. Its violet-blue hue is said to stimulate the higher mind, enhancing psychic abilities and spiritual perception. Tanzanite is believed to facilitate communication with higher realms, making it a favorite among those who practice meditation or energy work. It is also associated with new beginnings and major life changes, providing the courage and insight needed to navigate transitions. Some believe tanzanite can alleviate stress and anxiety, promoting a sense of calm and centeredness.
Care and Cleaning
The durability of a gemstone dictates how it should be cared for and cleaned. Proper maintenance ensures that birthstone jewelry remains beautiful for generations.
Turquoise, with its relatively low hardness and often porous nature, requires the most care. It is sensitive to chemicals, including cosmetics, perfumes, and even skin oils, which can cause discoloration or damage its surface. It should be cleaned with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals. It is best to put turquoise jewelry on after applying lotions and perfumes and to remove it before swimming, bathing, or engaging in physical activities where it could be struck or scratched. Stabilized turquoise is more resistant to these issues but should still be handled with care.
Zircon is a durable gem, but its high refractive index makes it somewhat brittle and prone to chipping if struck hard. It is sensitive to sudden temperature changes, which can cause internal stress and fracturing. Cleaning zircon jewelry is straightforward: use warm water, a mild dish soap, and a soft brush. Rinse thoroughly and dry with a soft cloth. Avoid ultrasonic cleaners and steam cleaners, as the vibrations and heat can potentially damage the stone. Due to its durability, zircon is suitable for a variety of jewelry settings, but protective settings like bezels are recommended for rings to prevent impact damage.
Tanzanite has a Mohs hardness of 6.5 to 7, but its cleavage (a tendency to break along flat planes) makes it vulnerable to impact. It is also sensitive to heat and sudden temperature changes. Cleaning tanzanite should be done with warm, soapy water and a soft brush. Never use ultrasonic cleaners or steam cleaners, as the vibrations and heat can cause the stone to fracture or crack. It is also advisable to avoid exposing tanzanite to extreme temperatures. Given its relative fragility, tanzanite is best suited for earrings, pendants, and other jewelry that is less likely to experience daily impact, such as rings.
Conclusion
December’s birthstones—turquoise, zircon, and tanzanite—offer a remarkable diversity within a shared color family. From the ancient, protective talisman of turquoise to the brilliant, wisdom-imbuing zircon and the transformative, modern tanzanite, each gem provides a unique narrative and set of characteristics. Their histories are deeply intertwined with human culture, spanning from ancient royal tombs to contemporary jewelry showcases. Geologically, they represent a fascinating spectrum, from the copper-rich, arid landscapes that birth turquoise to the billion-year-old crystals of zircon and the singular, tectonic marvel that is tanzanite. Their gemological properties, from hardness to refractive index, not only define their value and beauty but also guide their care. Ultimately, the choice of a December birthstone is a personal journey, allowing individuals to connect with a gem that resonates with their style, story, and spirit. Whether chosen for its historical significance, its dazzling brilliance, or its captivating color, any of these three stones makes a profound and beautiful statement for those born in the month of December.