For those born in the final month of the year, December offers a unique and diverse array of birthstones. Unlike most months, which are typically associated with a single gem, December is traditionally linked to multiple stones, providing a spectrum of colors and characteristics that capture the essence of winter. The primary December birthstones are turquoise and zircon, officially recognized in the modern list established in 1912. Over time, this list has expanded to include tanzanite and blue topaz, offering even more options for individuals seeking a gemstone that reflects their personal style and the season's cool, serene beauty. This article will explore the history, geological origins, gemological properties, and cultural significance of these four remarkable gemstones, drawing exclusively from authoritative sources to provide a thorough and expert overview for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore
The tradition of associating specific gemstones with calendar months is ancient, with roots tracing back to biblical descriptions of Aaron's breastplate and the foundation stones of the New Jerusalem. However, the modern standardized list was formalized in 1912 by the American National Association of Jewelers, which designated turquoise and zircon as the official birthstones for December. This list has been updated since, most notably with the addition of tanzanite in 2002 by the American Gem Trade Association, reflecting the industry's desire to offer more variety and highlight rare gems.
Turquoise boasts one of the longest histories among gemstones. Its use dates back over 5,000 years, with the oldest known turquoise mines located in ancient Egypt, dating to approximately 3200 BCE. The gem was prized for its distinctive robin's egg blue color and was extensively used in jewelry and ornamentation across the Middle East and by Native American cultures. Its name derives from the French "pierre turquoise," meaning "Turkish stone," as it reached Europe through gem markets in Constantinople (modern-day Istanbul). Turquoise was highly valued as an amulet, believed to offer protection against danger and bring good fortune. It was also cherished by lovers and married couples as a symbol of enduring relationships and friendship. Ancient Incas and Mayans offered turquoise to their gods, while Tibetans considered it a stone of fortune, health, and success, even using it as a form of currency. Native Americans of the Southwest associated the gem with youth and strength. A unique belief was that turquoise could warn its wearer of illness or danger by changing color and becoming pale.
Zircon has ancient origins as well, mentioned in Hebrew, Arabic, and Greek texts as early as the 5th century BCE. The word "zircon" is derived from the Persian "zargun," meaning "gold-colored," though the most prized varieties are colorless or blue. Historically, zircon's brilliant fire and wide range of colors led it to be used as an imitation for other gems, particularly diamonds. The colorless varieties were especially highly prized for their diamond-like appearance. Zircon is associated with clarity, wisdom, and a sense of balance.
Tanzanite is a relative newcomer to the gemstone world. Discovered in the late 1960s in the Merelani Hills of Tanzania, it was introduced to the global market in 1971. Its rapid rise to prominence is a testament to its stunning violet-blue color and unique pleochroism. The gem was named after the country of its origin and was championed by Tiffany & Co., which recognized its potential and marketed it heavily. Tanzanite symbolizes transformation, new beginnings, and fresh chapters in life, reflecting its modern discovery and captivating color shift.
Blue Topaz, while not one of the original December birthstones, has become a popular modern addition. Its inclusion in some lists, such as those from the American Gem Society, is due to its appealing blue hues and greater durability compared to some other December stones. Topaz itself has a long history, but the specific blue variety is largely a product of modern gem treatment, where colorless topaz is irradiated and heated to achieve stable blue colors. It represents a crisp, winter blue with extra durability, appealing to those who prefer a more robust gemstone for everyday wear.
Geological Formation and Sources
Understanding the formation and mining locations of these gemstones provides insight into their rarity and value.
Turquoise is a secondary mineral formed through the interaction of water with aluminum-rich rocks in arid regions. It is typically found in nodules or veins within host rock. Historically, major sources included Persia (modern-day Iran) and the Sinai Peninsula. Today, the most significant turquoise mines are located in the Southwestern United States (Arizona, New Mexico, Nevada), China, and Tibet. The quality of turquoise is heavily influenced by its matrix—the host rock in which it forms—and its color stability.
Zircon is a zirconium silicate (ZrSiO₄) that forms in igneous and metamorphic rocks. It is a common mineral found in many geological settings, but gem-quality zircon is rarer. Significant sources include Cambodia, Myanmar (Burma), Sri Lanka, Australia, and the United States (Colorado, California). Australian zircon often produces brownish to red hues, while Southeast Asian sources are known for producing the highly prized blue and colorless varieties. The gem is often recovered as a byproduct of mining other minerals.
Tanzanite is found exclusively in a small area of Tanzania, near Mount Kilimanjaro. It forms in a unique geological environment where intense heat and pressure transformed the mineral zoisite into the blue-violet tanzanite. The Merelani Hills are the only known commercial source, making tanzanite significantly rarer than diamond. Its formation is linked to the tectonic activity that created the East African Rift.
Blue Topaz is a variety of the topaz mineral, which forms in igneous rocks, particularly in pegmatites and rhyolites. While topaz is found in many locations worldwide (Brazil, Mexico, Sri Lanka, Nigeria), the intense blue color seen in gem-quality blue topaz is almost always the result of treatment. Natural blue topaz is extremely rare and typically very pale. Major sources for the treated blue topaz include Brazil, where large crystals are mined and then subjected to irradiation and heat to achieve deep, stable blue colors like Swiss Blue and London Blue.
Gemological Properties
The physical and optical properties of these gemstones dictate their durability, care requirements, and suitability for jewelry.
| Gemstone | Chemical Formula | Mohs Hardness | Crystal System | Refractive Index | Key Distinguishing Features |
|---|---|---|---|---|---|
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | Triclinic | 1.61 - 1.65 | Opaque to translucent, often has a matrix. Color ranges from sky blue to greenish. |
| Zircon | ZrSiO₄ | 6.5 - 7.5 | Tetragonal | 1.92 - 2.01 | High refractive index and strong dispersion ("fire"). Can be heat-treated to alter color. |
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | 6 - 7 | Orthorhombic | 1.69 - 1.70 | Strong pleochroism (shows blue, violet, and burgundy from different angles). |
| Blue Topaz | Al₂SiO₄(F,OH)₂ | 8 | Orthorhombic | 1.63 - 1.64 | Excellent hardness. Natural blue is rare; most are treated. Colors range from pale to deep "London Blue." |
Turquoise is relatively soft, with a Mohs hardness of 5 to 6. It is opaque to translucent and often contains a dark matrix of host rock, which can create attractive web-like patterns. Its color is its most valued feature, ranging from soft sky blue to greenish hues. Stability is a concern; some turquoise can fade or change color with prolonged exposure to light, heat, or chemicals.
Zircon is significantly harder and more durable, with a Mohs hardness of 6.5 to 7.5. It possesses a very high refractive index and strong dispersion, giving it exceptional brilliance and fire that can rival diamond. Zircon occurs in a variety of colors, including blue, yellow, brown, green, and red. The blue variety is often heat-treated from brown zircon to achieve its desired hue. It is important to note that zircon is not to be confused with synthetic cubic zirconia, a common diamond simulant.
Tanzanite has a Mohs hardness of 6 to 7, making it suitable for jewelry but requiring more care than harder gems. Its most remarkable property is strong trichroism (a form of pleochroism), where a single crystal can show three distinct colors: blue, violet, and burgundy-red depending on the viewing direction. This phenomenon is responsible for its captivating color shift. The gem is almost always heat-treated to remove brownish overtones and enhance its blue-violet color, a process that is stable and permanent.
Blue Topaz is one of the hardest of the December stones, with a Mohs hardness of 8. This makes it highly durable and resistant to scratching, ideal for rings and bracelets subjected to daily wear. As noted, the intense blue colors (like Swiss Blue and London Blue) are achieved through irradiation and heat treatment of colorless topaz. These treatments are stable and the color does not fade. Natural blue topaz is extremely rare and typically a very pale blue.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these gemstones are steeped in symbolism and metaphysical lore, which continues to influence their popularity.
Turquoise is universally regarded as a stone of protection, healing, and good fortune. It is believed to ground the wearer, provide a sense of calm, and ward off negative energy. Historically, it was thought to signal illness by changing color, and it remains a popular talisman for travelers. In relationships, it is said to promote fidelity and preserve friendship. Its association with the sky and water connects it to tranquility and emotional balance.
Zircon is associated with mental clarity, wisdom, and balance. It is believed to enhance focus, promote spiritual growth, and bring prosperity. Colorless zircon, with its diamond-like sparkle, is sometimes linked to purity and innocence. Blue zircon, in particular, is thought to aid in communication and self-expression.
Tanzanite, as a modern discovery, carries symbolism tied to transformation and new beginnings. Its unique color shift is seen as a metaphor for shifting perspectives and embracing change. It is often associated with heightened intuition, spiritual awareness, and the courage to embark on new life chapters. Its rarity and unique origin story add to its allure as a stone of distinction.
Blue Topaz symbolizes calm, clarity, and communication. Its cool blue color is associated with the throat chakra, making it a stone of truth and clear expression. It is believed to soothe stress, reduce anxiety, and promote honest communication. Its durability also symbolizes resilience and steadfastness.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, with requirements varying based on their physical properties.
Turquoise requires gentle handling due to its relative softness and porosity. It should be protected from harsh chemicals, perfumes, and prolonged exposure to sunlight, which can cause fading or discoloration. Clean turquoise jewelry with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and even mild soaps, which can penetrate the stone and damage it over time. Store it separately to prevent scratches from harder gems.
Zircon is fairly durable but can be brittle due to its crystal structure. It is sensitive to sudden temperature changes, which can cause fracture. Avoid wearing it during activities that risk impact. Cleaning can be done with warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe, but steam cleaning should be avoided. It is also advisable to keep zircon away from strong light and heat for extended periods, as some colored zircon can fade.
Tanzanite is relatively soft and has perfect cleavage in one direction, making it susceptible to chipping and cracking if knocked hard. It is highly recommended for protective settings like bezels, especially for rings. Cleaning should be done with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam, as vibrations and heat can damage the stone. Store it separately in a soft cloth to prevent scratches.
Blue Topaz, with its high hardness of 8, is one of the more durable options. It can withstand normal wear and is less prone to scratching. However, it is still sensitive to heat and sudden temperature changes, which could potentially damage the stone or its treatment. Cleaning is straightforward: use warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe, but steam cleaning is not recommended. As with all gemstones, avoid harsh chemicals and cosmetics.
Conclusion
December's birthstones offer a remarkable diversity, from the ancient, earthy allure of turquoise to the brilliant fire of zircon, the transformative hues of tanzanite, and the durable, icy blue of topaz. Each gemstone carries a rich history, unique geological story, and distinct set of properties that cater to different preferences and lifestyles. Whether one is drawn to the protective lore of turquoise, the clarity of zircon, the modern elegance of tanzanite, or the resilient beauty of blue topaz, there is a December stone that captures the essence of the winter month. Understanding their origins, properties, and care requirements allows enthusiasts and buyers to make informed choices, ensuring these beautiful gems can be cherished for generations.