December is a month of profound contrasts, marked by the stark beauty of winter in the Northern Hemisphere and the vibrant summer in the Southern Hemisphere. It is a time of ancient festivals, modern holidays, and celestial events, from the Geminid meteor shower to the winter solstice. Within this rich tapestry of cultural and natural history lies a special trio of gemstones assigned to those born in the twelfth month: turquoise, zircon, and tanzanite. Each of these stones carries its own unique narrative, from ancient symbols of good fortune to modern discoveries of breathtaking rarity. This article delves into the geological origins, gemological properties, historical significance, and cultural symbolism of December’s three birthstones, providing a comprehensive guide for enthusiasts, collectors, and anyone captivated by the allure of these remarkable minerals.
The Historical and Cultural Journey of December’s Birthstones
The tradition of associating specific gemstones with birth months has evolved over centuries, drawing from ancient beliefs, biblical references, and the 1912 standardization by the American National Association of Jewelers. December’s stones are a testament to this layered history, each representing a different era and cultural perspective.
Turquoise: The Ancient Talisman of Good Fortune
Turquoise stands as the most traditional and historically significant birthstone for December. For millennia, this opaque, sky-blue to greenish-blue mineral has been revered across civilizations. The provided sources note that turquoise is considered a symbol of good fortune and success, a belief that has persisted from ancient times to the present day. Its name itself derives from the French pierre turquoise, meaning "Turkish stone," reflecting its historical trade route through Turkey from its primary sources in Persia (modern-day Iran). While the sources do not detail specific ancient cultures, the enduring association with luck and protection aligns with global historical patterns where turquoise was worn as an amulet against harm and to attract prosperity. As the most traditional December stone, it represents the deep, ancient roots of birthstone lore.
Zircon: The Gem of Many Colors
Zircon is the second of December’s traditional birthstones. The sources highlight that zircon comes in a variety of colors but is most popular in its blue form. This versatility has allowed it to be appreciated for centuries, though its history is often overshadowed by its more famous blue counterpart. Zircon is one of the oldest minerals on Earth, with crystals dating back billions of years, yet its use as a December birthstone is a more modern convention. Its ability to mimic more expensive gems, such as diamonds, has led to both admiration and confusion. The blue variety, often achieved through heat treatment, became particularly popular in the 20th century as a more affordable alternative to sapphire, making it a staple in jewelry for those born in December.
Tanzanite: The Modern Marvel of Rarity
Tanzanite is the newest addition to the December birthstone family, a 20th-century discovery that has rapidly gained global acclaim. The sources state that tanzanite was discovered in Tanzania in 1967 and is rarer than diamonds. This singular origin point, a small mining area in the Merelani Hills of northern Tanzania, makes it one of the most geographically limited gemstones in the world. Its rapid rise to prominence is a modern gemological success story. The gem’s unique violet-blue to purplish-blue hue, which can display a dramatic trichroic effect (showing different colors from different angles), captivated the jewelry market. The American Gem Trade Association (AGTA) officially added tanzanite as a December birthstone in 2002, recognizing its significance and ensuring its place alongside turquoise and zircon for future generations.
Geological Formation and Sources
Understanding where these gems come from provides insight into their rarity and value. Each of December’s stones has a distinct geological story.
Turquoise Formation and Sources
Turquoise is a hydrous phosphate mineral that forms in arid regions where acidic, copper-rich groundwater percolates through rocks containing aluminum and phosphorus. Over millennia, this process creates nodules and veins of turquoise. The provided sources do not specify modern mining locations, but historically, the finest "Persian turquoise" came from Iran, known for its uniform sky-blue color. In the United States, significant deposits have been mined in Arizona, Nevada, and New Mexico, producing stones with a wider range of colors, often with distinctive matrix patterns.
Zircon Formation and Sources
Zircon (ZrSiO₄) is a zirconium silicate mineral that crystallizes from magma as it cools. It is a common accessory mineral in igneous and metamorphic rocks and is known for its exceptional durability. While the sources do not list specific zircon mining countries, the gem is found in a variety of locations worldwide, including Australia (a major producer of brown zircon), Cambodia, Sri Lanka, and Thailand. The blue zircon used in jewelry is typically produced by heating brown or yellow zircon crystals to high temperatures, a process that enhances its color and clarity.
Tanzanite Formation and Sources
Tanzanite’s formation is geologically unique. It is a variety of the mineral zoisite, colored by traces of vanadium. The process that created tanzanite is believed to have occurred approximately 585 million years ago when intense heat and pressure from tectonic plate movements transformed limestone into the blue zoisite crystals found today. The sources confirm its exclusive origin: Tanzania. Specifically, all known commercial deposits are located in a small, four-square-kilometer area in the Merelani Hills near Mount Kilimanjaro. This extreme rarity, with a single source, underscores why tanzanite is considered rarer than diamonds and contributes to its high value in the gem market.
Gemological Properties: A Scientific Profile
The physical and chemical properties of a gemstone determine its durability, appearance, and care requirements. The following table summarizes the key gemological characteristics of turquoise, zircon, and tanzanite, based on standard gemological data reflected in the sources’ descriptions.
| Gemstone | Chemical Formula | Crystal System | Mohs Hardness | Specific Gravity | Refractive Index | Key Properties & Treatments |
|---|---|---|---|---|---|---|
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | Triclinic | 5 - 6 | 2.60 - 2.90 | 1.61 - 1.65 | Opaque, often porous. Color ranges from sky blue to greenish blue. Often stabilized with wax or resin to enhance durability and color. |
| Zircon | ZrSiO₄ | Tetragonal | 6.5 - 7.5 | 3.90 - 4.73 | 1.92 - 2.01 | High dispersion ("fire"), often heat-treated to achieve blue color. Can be confused with synthetic cubic zirconia. |
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | Orthorhombic | 6 - 7 | 3.10 - 3.38 | 1.69 - 1.70 | Trichroic (displays blue, violet, and burgundy from different angles). Almost always heat-treated to produce its signature blue color. |
Color, Clarity, and Cut
- Turquoise: Valued for its vibrant, uniform color. High-quality turquoise is typically translucent to opaque. Clarity is assessed by the absence of dark matrix and even color distribution. It is commonly cut into cabochons for beads and inlays.
- Zircon: The most prized color is a vivid, pure blue, which is almost always the result of heat treatment. Clarity is important, as zircon can be included, but faceted cuts maximize its brilliance and fire.
- Tanzanite: Renowned for its intense violet-blue hue. The most desirable color is a rich, saturated blue with violet undertones. Clarity is typically good, with few inclusions. It is almost exclusively faceted (often in emerald or pear cuts) to showcase its trichroism and brilliance.
Durability and Wearability
Durability is a critical factor for jewelry. Turquoise (Mohs 5-6) is relatively soft and porous, making it susceptible to scratches, chemicals, and heat. It requires careful handling. Zircon (Mohs 6.5-7.5) is significantly harder and more durable, suitable for a variety of jewelry types, though its brittleness requires careful cutting and setting. Tanzanite (Mohs 6-7) is moderately hard but has perfect cleavage in one direction, meaning it can split if struck with force. It is best set in protective settings for rings and handled with care.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, December’s stones are rich in symbolic meaning and metaphysical lore.
- Turquoise: Universally recognized as a stone of good fortune and success. It is also widely believed to be a protective talisman, warding off negative energy and bringing peace to the wearer. Many cultures, including those of Native American and Persian heritage, have long associated turquoise with healing, wisdom, and spiritual grounding.
- Zircon: While the sources do not specify metaphysical beliefs for zircon, in broader gem lore, it is often associated with prosperity, honor, and purity. The blue variety, in particular, is linked to tranquility and clarity of mind, aligning with its calming color.
- Tanzanite: As a modern gem, its metaphysical associations are more contemporary. It is frequently described as a stone of transformation, believed to facilitate spiritual awakening and higher consciousness. Its unique trichroic nature is sometimes interpreted as representing the unification of mind, body, and spirit.
Care and Cleaning: Preserving Your December Gems
Proper care is essential to maintain the beauty and longevity of these birthstones, given their varying physical properties.
Turquoise Care
Due to its porosity and moderate hardness, turquoise requires gentle care. * Cleaning: Use only a soft, damp cloth. Avoid ultrasonic cleaners, steam cleaners, and chemical jewelry cleaners, as these can damage the stone or strip any stabilizing treatments. Never expose turquoise to lotions, perfumes, or hairspray. * Storage: Store separately in a soft pouch to prevent scratches. Avoid prolonged exposure to direct sunlight or heat, which can cause fading or cracking.
Zircon Care
Zircon is more durable but has specific vulnerabilities. * Cleaning: Safe to clean with warm, soapy water and a soft brush. Avoid sudden temperature changes, as zircon is susceptible to thermal shock, which can cause cracking. Ultrasonic cleaners are generally safe unless the stone has surface-reaching fractures. * Storage: Store in a fabric-lined box or separate compartment to avoid scratches from harder gems like diamonds or softer gems like turquoise.
Tanzanite Care
Tanzanite’s perfect cleavage makes it the most delicate of the three in terms of impact resistance. * Cleaning: Clean with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaners, as vibrations and heat can cause cleavage. Never use harsh chemicals. * Storage: Always store in a separate, padded compartment. It is advisable to remove tanzanite jewelry during physical activities, housework, or any situation where it might be struck.
Conclusion
The birthstones of December—turquoise, zircon, and tanzanite—offer a fascinating spectrum of geological wonders, historical depth, and cultural significance. From the ancient, sky-blue talisman of turquoise to the versatile, fiery brilliance of zircon and the modern, rare elegance of tanzanite, each stone tells a unique story. Their journey from the earth’s depths to the jewelry box is a testament to both natural processes and human artistry. For those born in December, these gems provide a personal connection to a month defined by transition, celebration, and the enduring beauty of the natural world. Whether chosen for their symbolic meanings, their stunning colors, or their remarkable properties, turquoise, zircon, and tanzanite remain timeless treasures, each worthy of appreciation and careful preservation.