December is a month of contrasts, marked by the quiet stillness of winter and the vibrant celebration of holidays. For those born in this final month of the year, their birthstones reflect this duality, offering a spectrum of blue hues that range from the earthy and opaque to the fiery and transparent. While many months are assigned a single gem, December is uniquely associated with three distinct traditional birthstones: Turquoise, Tanzanite, and Zircon. Each possesses a unique history, geological origin, and set of symbolic meanings, providing a rich palette for personal adornment and expression. This article delves into the comprehensive world of December's birthstones, exploring their ancient lore, geological formation, gemological properties, and enduring significance in modern gemology and jewelry.
History and Lore: From Ancient Calendars to Modern Designations
The concept of birthstones is not a modern invention but a tradition with roots stretching back millennia. The practice can be traced to ancient civilizations, including those of Egypt, Greece, and Rome, where gemstones were believed to hold mystical and healing properties, and were often linked to specific periods of the year or astrological signs. Over time, these beliefs evolved into more formalized systems.
For December, the historical record reveals a fascinating and sometimes overlapping set of stones. The traditional and most enduring gemstone for December is Turquoise. Its association is ancient, appearing in the old Polish and Russian calendars. Furthermore, before its formal adoption as a monthly birthstone, Turquoise served as a zodiac stone for Sagittarius, the astrological sign that spans late November and most of December. This deep-seated connection is immortalized in 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."
Zircon also holds a traditional claim to December. It remained the birthstone for December in modern U.S. gemology after it replaced Lapis Lazuli in 1952. Lapis Lazuli itself was a modern birthstone for December in the United States until February 2013, when the American Gem Trade Association made the final switch to Zircon. This history highlights the dynamic nature of birthstone lists, which can be updated by trade organizations to reflect availability, popularity, and market trends.
The newest addition to the December family is Tanzanite. Recognized as a December birthstone in the United States in 2002, it had already been acknowledged as such in Britain by that time. Its introduction expanded the color and style options for December babies, offering a gemstone with a compelling, modern discovery story.
Beyond these three, the historical tapestry of December birthstones is even more varied. Some sources list nine different stones for the month, categorized by tradition and origin. These include: * Modern: Turquoise & Tanzanite * Alternate-US: Zircon & Blue Topaz * Traditional: Bloodstone, Ruby, Zircon, & Lapis Lazuli * Ancient: Ruby, Turquoise, & Chrysoprase * Tibetan: Onyx * Indian: Cat’s Eye
This proliferation of stones underscores the cultural significance of the month and the desire to offer a wide array of choices. Bloodstone (heliotrope), a green chalcedony with red inclusions, was a traditional December stone from as far back as the 15th century, believed to enhance courage. Onyx, particularly black Onyx, is the birthstone for December in the old Tibetan calendar and is considered a grounding stone. Lapis Lazuli, an opaque deep-blue stone mottled with yellow and white, was believed to heighten awareness and free a person of negativity. Even Ruby, the primary birthstone for Capricorn (which begins on December 22nd), is sometimes associated with the month. This historical diversity confirms that the "birthstone for December" is not a singular answer but a rich collection, though the modern consensus has crystallized around three primary blue gems.
Geological Formation and Sources: From Groundwater to Metamorphic Heat
The diverse origins of December's birthstones are a testament to the varied geological processes that create gemstones. Each stone forms under distinct conditions and is sourced from specific, often limited, locations around the globe.
Turquoise is an opaque mineral formed through a secondary process. It is not typically found in primary igneous or metamorphic rock like many other gems. Instead, Turquoise forms when groundwater containing copper seeps into bedrock, often arid regions. Over time, this copper-rich water reacts with aluminum and phosphorus-bearing minerals in the host rock, slowly depositing the turquoise mineral (hydrated copper aluminum phosphate) in fractures and cavities. The distinctive dark lines and shapes seen in many turquoise specimens are not part of the gem itself but are inclusions of the surrounding host rock, known as matrix. Major sources for Turquoise include the United States (particularly the Southwest), Iran, and Egypt. The name "Turquoise" itself is derived from the French pierre turquoise, meaning "stone of Turkey," as it was brought to Europe from Turkish bazaars.
In stark contrast, Tanzanite is a product of high-temperature metamorphic processes. It is a variety of the mineral zoisite and was first discovered in 1967 in the Merelani Hills of northern Tanzania, near Mount Kilimanjaro—a location so specific that the gemstone is named for its country of origin. The geological conditions required for its formation are exceptionally rare, making it one of the most geographically limited gemstones in the world. Its vibrant blue-to-purple color is the result of heat treatment of the raw mineral, which is typically brownish in its natural state.
Zircon, not to be confused with the synthetic cubic zirconia, is a natural mineral with the chemical formula ZrSiO₄. It is one of the oldest minerals on Earth, with crystals found in ancient bedrock. Zircon forms as an accessory mineral in igneous and metamorphic rocks. It can be found in a rainbow of colors, but the blue variety, which is the most popular for December, is often the result of heat treatment applied to brownish zircon crystals. While Zircon is found in many locations worldwide, including Australia, Cambodia, and the United States, the high-quality blue stones suitable for gemstones come from a more limited set of sources.
The following table summarizes the key geological and source information for the three primary December birthstones:
| Gemstone | Geological Formation | Key Characteristics | Primary Sources | Color Range (for December) |
|---|---|---|---|---|
| Turquoise | Secondary mineral formed by copper-rich groundwater in arid bedrock. | Opaque, often contains matrix (host rock inclusions). | USA (Southwest), Iran, Egypt. | Blue to greenish hues. |
| Tanzanite | Metamorphic process; heat treatment required for blue color. | Transparent, pleochroic (shows different colors from different angles). | Tanzania (Merelani Hills). | Rich violet-blue to pure blue. |
| Zircon | Accessory mineral in igneous and metamorphic rocks. | High refractive index and dispersion, giving it exceptional brilliance. | Australia, Cambodia, USA, others. | Bright, clear blue (treated). |
Gemological Properties: The Science Behind the Beauty
Understanding the physical and optical properties of a gemstone is crucial for appreciating its value, durability, and suitability for jewelry. The three December birthstones differ significantly in these aspects.
Turquoise is prized for its unique opacity and distinctive color. It is a phosphate mineral with a hardness of 5 to 6 on the Mohs scale, making it relatively soft and susceptible to scratching and damage. This lower hardness means it requires careful handling and is often set in protective settings like bezels for jewelry. Its chemical composition is a hydrated copper aluminum phosphate. Because it is porous, Turquoise can be stabilized with resins or waxes to enhance its durability and color. Its value is influenced by color (even, vibrant blue is most prized), the presence and pattern of matrix, and overall uniformity.
Tanzanite is a transparent gemstone known for its stunning pleochroism—the property of displaying different colors when viewed from different crystal directions. A single tanzanite crystal can show blue, violet, and burgundy hues. With a hardness of 6.5 to 7 on the Mohs scale, it is more durable than Turquoise but still requires care. It is a variety of zoisite, and its chemical formula is Ca₂Al₃(SiO₄)₃(OH). Its value is determined by the intensity of its blue color, clarity, and size. The finest tanzanite exhibits a deep, saturated violet-blue.
Zircon is one of the most brilliant of all natural gemstones. Its high refractive index (1.92-2.01) and very high dispersion (0.039) give it exceptional fire and sparkle, often compared to that of diamond. With a hardness of 6.5 to 7.5 on the Mohs scale, it is reasonably durable for jewelry, though it can be brittle due to its crystal structure. Zircon is a zirconium silicate (ZrSiO₄). While it occurs in many colors, the blue variety used for December birthstones is typically created by heating brown zircon crystals to produce a stable, vivid blue. The value of blue zircon is based on its color saturation, clarity, and cut quality. Its brilliance makes it a popular choice for faceted jewelry pieces.
Symbolism and Metaphysical Beliefs: A Legacy of Meaning
Beyond their physical beauty, December's birthstones are steeped in symbolic meaning and metaphysical lore, beliefs that have been passed down through generations.
Turquoise has long been associated with protection, good fortune, and success. Across many cultures, it was believed to be a powerful talisman, warding off negative energy and harm. It is also linked to emotional balance and the relief of mental tension, as noted in historical beliefs. Its connection to water and sky in its color and formation has made it a symbol of tranquility and peace.
Tanzanite, as a modern discovery, carries more contemporary symbolism. It is often associated with transformation, new beginnings, and intuition. Its dramatic color change from brown to blue through heat treatment is seen as a metaphor for personal growth and spiritual awakening. It is believed to facilitate communication with higher realms and enhance spiritual insight.
Zircon is traditionally linked to clarity, wisdom, and a sense of balance. It is thought to promote prosperity and honor, and to help its wearer achieve peace of mind. The brilliant sparkle of zircon has also associated it with light and clarity of thought, making it a stone for those seeking truth and understanding.
While the primary stones carry these specific meanings, other historical December stones also have their own symbolism. Bloodstone was believed to enhance courage and physical strength. Onyx is considered a grounding stone, offering protection from negativity. Lapis Lazuli was thought to expand perspective and heighten awareness. This wealth of symbolic options allows individuals to choose a December stone that resonates with their personal aspirations and beliefs.
Care and Cleaning: Preserving Your December Gem
The different physical properties of these gemstones dictate specific care instructions to ensure their longevity and beauty.
Turquoise, with its lower hardness and potential porosity, is the most delicate of the three. It should be protected from harsh chemicals, including household cleaners, cosmetics, and even sweat, which can cause discoloration and damage. Cleaning should be done gently with a soft, damp cloth and mild soap, avoiding ultrasonic cleaners and steam. It should be stored separately to prevent scratching from harder stones.
Tanzanite is also relatively soft and can be brittle, making it prone to chipping or cracking if struck. It is sensitive to rapid temperature changes and should not be exposed to heat. Cleaning can be done with warm, soapy water and a soft brush, but ultrasonic and steam cleaners should be avoided. Given its fragility, it is often set in protective settings for rings.
Zircon, while harder, has perfect cleavage in two directions, meaning it can split along certain planes if struck with force. This makes it susceptible to chipping, especially in faceted designs. It is generally stable under normal conditions but should be protected from sharp blows. Cleaning with warm, soapy water and a soft brush is safe. Avoid mechanical vibrations and extreme temperature changes. For all three stones, removing jewelry before physical activities, cleaning, or applying lotions is the best practice for preservation.
Conclusion
The birthstones of December—Turquoise, Tanzanite, and Zircon—offer a remarkable trio that spans history, geology, and symbolism. From the ancient, earthy warmth of Turquoise, formed in the arid landscapes of our planet, to the fiery, transformative discovery of Tanzanite from a single location in Tanzania, and the brilliant, timeless sparkle of Zircon, these gems provide a diverse array of choices for those born in the last month of the year. Their shared association with the color blue, a hue of depth and tranquility, unites them as symbols of winter's cool beauty. Whether chosen for its historical significance, unique geological story, or metaphysical properties, each December birthstone carries a legacy of meaning, making it a profoundly personal and enduring treasure.