The twelfth month of the year is uniquely distinguished by a trio of captivating blue birthstones: Tanzanite, Turquoise, and Zircon. Each gem offers a distinct shade and story, from the vibrant violet-blue of a recently discovered mineral to the ancient, sky-hued talismans of desert cultures and the fiery, diamond-like brilliance of a traditional gemstone. For individuals born in December, these three stones provide a spectrum of choices, allowing for personal expression in jewelry that carries both aesthetic appeal and deep-seated symbolism. This article delves into the history, geology, gemological properties, and cultural significance of Tanzanite, Turquoise, and Zircon, drawing exclusively from authoritative sources to provide a comprehensive guide for gemstone enthusiasts, collectors, and those seeking the perfect birthstone.
History and Lore
The historical narratives of these December birthstones span millennia, from ancient civilizations to modern gemological breakthroughs. Turquoise holds the most ancient lineage, with evidence of its use dating back over two thousand years in the Southwestern United States. Here, Native American cultures crafted beads, pendants, inlay work, and small sculptures from this opaque mineral, embedding it deeply into their artistic and spiritual traditions. This long-standing cultural integration continues today, as turquoise remains an important element of Southwestern culture and identity. Its journey from an ancient tribal gemstone to a modern birthstone is a testament to its enduring appeal.
Zircon, in contrast, has a history intertwined with both confusion and prestige. For centuries, it was mistaken for other gemstones, notably the blue variety for sapphire, due to its high luster and brilliance. This confusion, however, did not diminish its value. Zircon has been used in jewelry for a very long time, prized for its exceptional fire and sparkle. Its status as a traditional December birthstone was solidified over time, and it continues to be a celebrated gem for those born in the last month of the year.
Tanzanite is the newest member of this trio, with its history beginning only in the late 20th century. Discovered in a single, small geographic area in Tanzania, this blue to violet variety of zoisite was introduced to the global gemstone market relatively recently. Its rapid rise to prominence led to its official addition as a December birthstone by the American Gem Trade Association, marking a significant update to the modern birthstone chart. This addition was the first major change to the list in 50 years, highlighting the dynamic nature of birthstone traditions.
The evolution of the birthstone chart itself provides context for these gems' inclusion. The modern birthstone chart, standardized by the National Association of Jewelers (now Jewelers of America) in 1912, has undergone several revisions to reflect new discoveries and market trends. The addition of Tanzanite in 2002, and the continued presence of Turquoise and Zircon, illustrates how the list adapts to incorporate both ancient stones of lore and modern gems of remarkable beauty and significance.
Geological Formation and Sources
Understanding the origins of these gems enhances appreciation for their unique characteristics. Each of the December birthstones forms under different geological conditions and is sourced from specific regions of the world.
Turquoise is an opaque, blue to blue-green to yellowish green mineral. Its formation typically occurs in arid regions where acidic, copper-rich groundwater interacts with rocks containing aluminum and phosphorus. This process can take millions of years, forming veins or nodules within host rock. The most prized turquoise often comes from specific mining locations, such as the American Southwest (e.g., Arizona, New Mexico, Nevada), Egypt, Iran, and China. The color variation—from sky blue to greenish hues—is largely determined by the amount of copper (blue) and iron (green) present during formation. As an opaque stone, it is typically cut into cabochon shapes, often freeform to maximize the use of the rough material.
Zircon is a mineral composed of zirconium silicate (ZrSiO₄). It is one of the oldest minerals on Earth, with some crystals dating back billions of years. Zircon forms in igneous and metamorphic rocks, often as small, prismatic crystals. Major commercial sources include Australia, Cambodia, Myanmar, and Sri Lanka. Australia is particularly known for producing brownish zircon, which is often heat-treated to produce a vibrant blue color. The gem's high refractive index and strong dispersion (fire) are responsible for its diamond-like brilliance. It is important to note that zircon is a natural mineral, distinct from synthetic cubic zirconia, which is a common diamond simulant.
Tanzanite is the blue to violet variety of the mineral zoisite. It is found in a very limited geographic area in the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This locality is the world's only significant commercial source, making tanzanite exceptionally rare. The gem forms through a complex geological process involving the metamorphism of limestone and other rocks, with heat and pressure causing the presence of vanadium to impart the stone's distinctive color. The limited geographic source and its recent discovery contribute to its rarity and desirability. Most tanzanite on the market is heat-treated to enhance its color, transforming brownish or yellowish zoisite into the prized violet-blue hue.
Gemological Properties
The physical and optical properties of Tanzanite, Turquoise, and Zircon differ significantly, influencing their durability, appearance, and care requirements. The following table summarizes key gemological data for each stone, based on established gemological sources.
| Gemstone | Chemical Formula | Mohs Hardness | Crystal System | Refractive Index | Key Properties |
|---|---|---|---|---|---|
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | 6.5 - 7 | Orthorhombic | 1.690 - 1.700 | Pleochroic (blue, violet, burgundy); trichroic; typically heat-treated; perfect cleavage. |
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | Triclinic | 1.610 - 1.650 | Opaque; color due to copper; often stabilized with resin; low hardness, prone to scratching. |
| Zircon | ZrSiO₄ | 6.5 - 7.5 | Tetragonal | 1.920 - 2.010 | High refractive index; high dispersion (fire); strong birefringence; can be heat-treated for color. |
Tanzanite is a relatively recent addition to the gemological world. It exhibits a remarkable trichroism, meaning it can display three different colors—typically blue, violet, and burgundy—from different crystal directions. This property, combined with its pleochroism, makes cutting an art to maximize the desired color in a finished gem. With a Mohs hardness of 6.5 to 7, it is moderately durable but can be prone to chipping due to its perfect cleavage in one direction. This cleavage means that a sharp blow can cause the stone to split along a specific plane, making it important to handle it with care and set it in protective jewelry.
Turquoise is prized for its opaque, waxy luster and distinctive color. Its hardness is relatively low, ranging from 5 to 6 on the Mohs scale, making it susceptible to scratching and wear. It also has a porous structure, which can cause it to absorb oils and chemicals, potentially leading to discoloration. To enhance durability and color stability, much of the commercial turquoise on the market is stabilized—treated with a clear resin or wax to fill its pores. This process makes the stone more resistant to damage and helps maintain its color over time. Because of its opacity and relative softness, turquoise is almost always cut into cabochons rather than faceted gems.
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 defining characteristic is its high refractive index (1.920-2.010) and exceptional dispersion (0.039), which gives it a fire and sparkle that can rival diamond. However, zircon also exhibits strong birefringence (double refraction), which can cause facets to appear doubled under magnification. This property requires skilled cutting to minimize its visual impact. Natural zircon occurs in a variety of colors, including colorless, yellow, brown, green, and blue. The blue variety, often seen in birthstone charts, is frequently produced by heat-treating brown zircon, a common and accepted practice in the gem trade.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these December birthstones are steeped in symbolism and metaphysical beliefs that have been attributed to them across various cultures and eras.
Turquoise has long been associated with protection, healing, and wisdom. In many Native American cultures, it is considered a sacred stone, a conduit to the sky and a symbol of spiritual grounding. Historically, it was believed to ward off evil and protect the wearer from harm, particularly during travel. Its color, reminiscent of the sky and water, is linked to tranquility, calmness, and emotional balance. For those born in December, turquoise is often seen as a talisman of good fortune, success, and overall well-being.
Zircon has a rich history of beliefs associated with it. In the Middle Ages, it was thought to promote honor, purity, and prosperity. It was also believed to help with sleep and induce peaceful dreams when placed under a pillow. Some traditions hold that zircon stimulates the root chakra, providing a sense of grounding and stability. The stone's brilliant fire was seen as a symbol of light and energy, and it was sometimes used as a protective amulet against negative energies.
Tanzanite, being a modern discovery, has more contemporary metaphysical associations. It is often linked to higher consciousness and spiritual awakening. Many believe that tanzanite can facilitate communication with higher realms, enhance intuition, and promote a sense of calm and clarity. Its unique trichroic nature—representing the past, present, and future—is sometimes interpreted symbolically, encouraging the wearer to embrace transformation and spiritual growth. For December-born individuals, tanzanite is considered a stone of new beginnings and heightened perception.
It is important to note that while these metaphysical beliefs are widely held within certain communities and alternative healing practices, they are not scientifically verified and fall outside the realm of gemological science. However, for many jewelry buyers and enthusiasts, these symbolic meanings add a layer of personal significance to their chosen birthstone.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone. The distinct properties of Tanzanite, Turquoise, and Zircon necessitate specific handling and cleaning methods.
Tanzanite requires careful handling due to its perfect cleavage and moderate hardness (6.5-7). It should be protected from sharp blows and hard impacts. Cleaning can be done using warm, soapy water and a soft brush, but it should never be subjected to ultrasonic or steam cleaners, as the vibrations and heat can cause damage, especially if the stone has any inclusions or fractures. It is also advisable to remove tanzanite jewelry before engaging in physical activities or household chores.
Turquoise, with its lower hardness (5-6) and porous nature, is the most delicate of the three. It should be kept away from chemicals, cosmetics, perfumes, and even excessive perspiration, as these can cause discoloration or damage the stone's surface. Cleaning should be gentle: use a soft, dry cloth to wipe away dirt and oils. If necessary, a slightly damp cloth can be used, but the stone should be dried immediately and thoroughly. Avoid soaking turquoise in water, as this can affect any stabilizing resins. Ultrasonic and steam cleaners are strictly not recommended.
Zircon is relatively durable due to its hardness, but it can be brittle and is prone to chipping if struck. Its strong birefringence also means that it can be more susceptible to stress from certain settings. Cleaning is generally safe with warm, soapy water and a soft brush. However, due to its brittleness, avoid sudden temperature changes, which could cause internal stress. As with the other stones, ultrasonic cleaners are not recommended, as the vibrations could potentially damage a zircon that has existing inclusions or fractures.
For all three gemstones, the best practice is to store them separately in a soft cloth or padded compartment of a jewelry box to prevent scratching by harder stones. Regular inspection of settings is also recommended to ensure the stones remain secure.
Conclusion
Tanzanite, Turquoise, and Zircon together form a distinguished and diverse group of birthstones for the month of December. Their stories range from the ancient and earthy origins of turquoise, a stone of protection and cultural heritage, to the fiery, diamond-like brilliance of zircon, a gem of historical confusion and enduring elegance, to the vibrant, modern allure of tanzanite, a rare mineral born from a single valley in Tanzania. Each gem offers a unique palette of blue—from the opaque sky-hued turquoise to the deep violet of tanzanite and the brilliant, multifaceted blue of treated zircon—catering to a wide range of personal styles and preferences.
Understanding their geological origins, gemological properties, and the beliefs they inspire allows for a deeper appreciation of these remarkable stones. Whether chosen for its metaphysical properties, its historical significance, or simply its captivating color, any of the December birthstones serves as a beautiful and meaningful adornment. For those born in December, the selection of Tanzanite, Turquoise, or Zircon is not merely a choice of jewelry but a connection to a rich tapestry of geological time, human history, and personal expression.