December is unique in the world of gemology, holding the distinction of having the most widely recognized birthstones of any month. While most months are associated with a single gem, December offers a quartet of radiant options: Turquoise, Tanzanite, Blue Topaz, and Zircon. This abundance is not a recent marketing invention but a reflection of historical evolution, where ancient traditions were expanded in the 20th century to include stones of greater variety, color, and accessibility. Each of these gems brings its own story, from ancient civilizations to modern mines, offering a diverse palette of blues and greens that capture the essence of winter's chill and the sparkle of holiday celebrations. This article provides a detailed exploration of each December birthstone, examining their historical significance, geological origins, gemological properties, and the practical considerations for care and selection, drawing exclusively from the provided source materials.
History and Lore: The Evolution of December's Gems
The tradition of birthstones has deep roots, with origins tracing back to ancient cultures that attributed specific stones to months for their perceived protective and healing powers. For December, the historical narrative is particularly layered, involving multiple stones across different calendars and regions. The modern list of December birthstones is a synthesis of these ancient traditions and contemporary additions.
Turquoise stands as the most ancient and traditional birthstone for December. According to the Gregorian birthstone poem, "If cold December gave you birth, / The month of snow and ice and mirth, / Place on your hand a turquoise blue; / Success will bless whate’er you do." This gemstone was recognized in old Polish and Russian calendars and was even a zodiac stone for Sagittarius, which partially falls in December. Its history as a December stone is long and continuous, making it the cornerstone of the month's gemological heritage.
Zircon also has a strong claim to tradition. It was the traditional birthstone for December and remains a modern birthstone in U.S. gemology. Notably, it replaced lapis lazuli in the U.S. birthstone list in 1952, a change that highlights the evolving nature of these lists to reflect market availability and consumer preference.
The 20th century saw significant expansions to the birthstone list. Blue Topaz and Tanzanite were added during this period to offer more variety. Blue Topaz, with its peaceful blue hues, was incorporated as a modern option, while Tanzanite, a relatively new discovery in the gem world, brought a luxurious and trendy color to the December palette. This expansion was driven by a desire to provide options in terms of availability, color, and cost, ensuring that everyone could find a gemstone that resonated with their taste and budget.
The reason December has four birthstones is rooted in this historical and modern development. Originally, lists consisted of ancient, traditional stones, but they were expanded in the 20th century to represent modern times. This evolution allowed for the inclusion of stones like Blue Topaz and Tanzanite, which align with winter colors and contemporary fashion trends. Consequently, December's gemstone history is not a single thread but a tapestry woven from ancient beliefs and modern market dynamics.
Geological Formation and Sources
The geographic diversity of December's birthstones adds to their allure, with each gem sourced from distinct and often unique locations around the world. Understanding where these stones are mined provides insight into their rarity and geological story.
Turquoise is mined in several key regions. The primary sources include the southwestern United States, with notable deposits in Arizona and Nevada. Internationally, Iran is famous for its Persian turquoise, and China also contributes to the global supply. This stone's formation is typically in arid regions where acidic waters percolate through rocks containing copper, aluminum, and phosphorus, depositing turquoise in veins or nodules.
Zircon is sourced from a variety of countries, including Sri Lanka, Cambodia, Myanmar, and Australia. These locations are known for producing zircon crystals that can be cut into brilliant gemstones. Zircon forms in igneous and metamorphic rocks, often as a primary mineral in granitic pegmatites or as a detrital mineral in sedimentary deposits.
Tanzanite has the most exclusive origin of the four. It is found exclusively in the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. This single-source location makes tanzanite particularly rare and valuable. The gem forms under specific geological conditions where heat and pressure transform zoisite into the blue-violet variety known as tanzanite.
Blue Topaz is mined in several countries, with Brazil being the largest producer. Other sources include Nigeria, Sri Lanka, and China. Topaz forms in pegmatites and hydrothermal veins, often in association with fluorite and other minerals. The blue color in topaz is typically achieved through irradiation and heat treatment of colorless or pale topaz, a common practice in the gem industry.
The geographic distribution of these stones—from the deserts of the American Southwest to the hills of Tanzania—underscores the global nature of the gem trade and the unique geological conditions required for each gem's formation.
Gemological Properties: A Scientific Overview
Understanding the physical and chemical properties of these gems is essential for gemologists, jewelers, and buyers alike. Each of December's birthstones has distinct characteristics that influence its durability, appearance, and value.
Turquoise
Turquoise is an opaque phosphate mineral with a hardness of 5 to 6 on the Mohs scale. Its chemical formula is CuAl₆(PO₄)₄(OH)₈·4H₂O, indicating the presence of copper, which gives it its characteristic blue to green colors. Turquoise often exhibits a porous structure and can contain matrix (host rock) inclusions, which are part of its natural character. Due to its moderate hardness and porosity, turquoise is susceptible to damage from chemicals, heat, and prolonged exposure to moisture.
Zircon
Zircon (ZrSiO₄) is a hard gemstone with a Mohs hardness of 7.5, making it relatively durable for jewelry. It has a high refractive index (1.92–2.01) and strong dispersion (0.039), which gives it a brilliant sparkle often compared to diamonds. Zircon comes in a variety of colors, but the blue variety is most associated with December. However, it's important to note that blue zircon is typically heat-treated to achieve its color. Zircon can be confused with cubic zirconia, a synthetic diamond simulant, but they are entirely different materials.
Tanzanite
Tanzanite is a variety of the mineral zoisite, with a chemical formula of Ca₂Al₃(SiO₄)₃(OH). It has a hardness of 6.5 to 7 on the Mohs scale, making it moderately durable but requiring careful handling. Its most striking feature is its trichroism—the ability to show different colors (blue, violet, and burgundy) when viewed from different angles. The primary source of tanzanite is the Merelani Hills in Tanzania, and its exclusive origin contributes to its value. Most tanzanite is heat-treated to enhance its blue color, a standard and accepted practice in the gem trade.
Blue Topaz
Blue topaz is a silicate mineral (Al₂SiO₄(F,OH)₂) with a hardness of 8 on the Mohs scale, making it one of the harder December birthstones and suitable for everyday wear. Its color ranges from light sky blue to deep London blue, achieved through irradiation and heat treatment of colorless topaz. Blue topaz is often faceted to maximize its brilliance and is a popular choice for a variety of jewelry settings. Its durability and affordability have made it a modern favorite.
Comparative Properties
The following table summarizes key gemological properties of the four December birthstones based on the provided sources:
| Gemstone | Mineral Family | Chemical Formula | Mohs Hardness | Key Properties | Primary Color |
|---|---|---|---|---|---|
| Turquoise | Phosphate | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5–6 | Opaque, often porous, can contain matrix | Blue to green |
| Zircon | Silicate | ZrSiO₄ | 7.5–8 | High refractive index, strong dispersion | Blue (often heat-treated) |
| Tanzanite | Zoisite (Silicate) | Ca₂Al₃(SiO₄)₃(OH) | 6.5–7 | Trichroic (blue, violet, burgundy) | Blue-violet |
| Blue Topaz | Silicate | Al₂SiO₄(F,OH)₂ | 8 | Durable, faceted for brilliance | Light to deep blue |
This comparison highlights the range of hardness and durability among December's gems, with Blue Topaz and Zircon being the hardest and most suitable for rings and daily wear, while Turquoise requires more careful handling.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been imbued with symbolic meanings and metaphysical properties. December's birthstones are no exception, each carrying a legacy of beliefs and associations.
Turquoise is widely believed to be a stone of protection, luck, and healing. As mentioned in the sources, it is thought to relieve mental tension and increase luck. Its blue color is often associated with the sky and water, symbolizing tranquility and wisdom. In many cultures, turquoise is considered a sacred stone that connects the wearer to the spiritual world.
Zircon is often associated with wisdom, honor, and purity. It is believed to promote prosperity and protect against negative energy. The brilliant sparkle of zircon has led to its association with clarity of thought and spiritual enlightenment.
Tanzanite, being a relatively new discovery, lacks the ancient lore of turquoise or zircon. However, it is quickly gaining symbolic significance as a stone of transformation and new beginnings. Its unique trichroic colors are seen as representing the multifaceted nature of life and the ability to see beyond the surface.
Blue Topaz is associated with calm, clarity, and communication. Its soothing blue hues are believed to promote emotional balance and reduce stress. In modern metaphysical beliefs, blue topaz is often linked to the throat chakra, enhancing truthful expression and creative communication.
While these beliefs are popular among enthusiasts, it is important to note that they are based on cultural traditions and modern metaphysical practices rather than scientific evidence. For the gemologist, the primary value of these stones lies in their geological and gemological properties, but for many wearers, the symbolic meaning adds a personal dimension to their jewelry.
Care and Cleaning: Practical Maintenance
Proper care is essential to maintain the beauty and longevity of any gemstone. The durability of December's birthstones varies significantly, requiring tailored maintenance approaches.
Turquoise is the most delicate of the four. With a hardness of only 5–6 and a porous structure, it is susceptible to scratches, chemicals, and moisture. It should be cleaned with a soft, dry cloth and stored separately from other jewelry to avoid abrasion. Avoid exposing turquoise to perfumes, lotions, or cleaning agents, as these can damage its surface and alter its color. It is also advisable to remove turquoise jewelry before swimming or bathing.
Zircon, with a hardness of 7.5–8, is relatively durable but can be brittle due to its crystal structure. It should be protected from sharp blows and extreme temperature changes. Cleaning can be done with warm water, mild soap, and a soft brush. Ultrasonic cleaners are generally safe for zircon, but steam cleaning should be avoided.
Tanzanite has a hardness of 6.5–7, making it moderately durable but still prone to scratching and chipping. It is sensitive to heat and should not be exposed to high temperatures or rapid temperature changes. Cleaning with a soft brush and mild detergent is recommended. Avoid ultrasonic and steam cleaners, as they can cause damage.
Blue Topaz is the most durable of the December birthstones, with a hardness of 8. It is resistant to scratching and can withstand daily wear. However, it can be sensitive to sudden temperature changes and may fracture if subjected to extreme conditions. Cleaning is straightforward: use warm soapy water and a soft brush. Ultrasonic cleaners are generally safe, but caution is advised with steam cleaners.
For all gemstones, it is best to remove jewelry during physical activities, household chores, or exposure to harsh chemicals. Regular inspection by a professional jeweler is recommended to check for loose settings or damage, especially for rings and bracelets that experience frequent wear.
Conclusion
December's four birthstones—Turquoise, Tanzanite, Blue Topaz, and Zircon—offer a remarkable diversity in color, history, and properties. From the ancient, protective qualities of turquoise to the modern brilliance of blue topaz, each gem provides a unique connection to the month of December. Their geological origins span the globe, from the deserts of Arizona to the hills of Tanzania, and their gemological properties range from the delicate opacity of turquoise to the dazzling sparkle of zircon. Whether chosen for their symbolic meanings, aesthetic appeal, or durability, these stones continue to captivate gemstone enthusiasts, jewelry buyers, and students of gemology alike. As with any gemstone, understanding their individual characteristics and care requirements ensures that these December jewels can be cherished for generations.