The final month of the year, December, is a period rich in cultural traditions, astronomical events, and deep-seated symbolism. For those born in this month, their birthstones are as diverse and storied as the holidays that define the season. While many cultures associate December with the deep blue of turquoise, the month's official birthstones encompass a trio of distinct gems: turquoise, zircon, and tanzanite. Each possesses unique geological origins, gemological properties, and layers of historical meaning, contributing to a collective narrative of protection, clarity, and transformation. This article delves into the science, history, and lore of these December birthstones, exploring how they have come to symbolize good fortune, success, and the enduring light of winter celebrations.
History and Lore: A Trio of Timeless Gems
The tradition of assigning specific stones to birth months has evolved over centuries, with December's list being particularly notable for its historical depth and modern additions. The primary and most ancient of these is turquoise, a stone whose name itself derives from the French pierre turquoise, meaning "Turkish stone," reflecting its historic trade routes from Persia to Europe. As noted in historical accounts, turquoise has long been considered a symbol of good fortune and success. Its use spans millennia, from ancient Egyptian amulets to the intricate jewelry of Native American tribes, who valued it for its protective qualities and connection to the sky and water.
The journey of December's birthstones continued in the 20th century. Zircon, a gem often confused with the synthetic cubic zirconia, has a history that predates its modern birthstone status. It is one of the oldest minerals on Earth, with some crystals dating back billions of years. For much of its history, zircon was appreciated for its fiery brilliance and was often used as a diamond simulant. Its inclusion as a December birthstone is a more recent formalization, adding a gem of high clarity and luster to the month's palette.
The most recent addition to the December birthstone family is tanzanite. Discovered in the late 1960s near Mount Kilimanjaro in Tanzania, this gemstone was introduced to the world in the 1970s. Its vivid blue-violet hue, a result of specific geological conditions, was quickly recognized for its rarity and beauty. In 2002, the American Gem Trade Association (AGTA) officially named tanzanite an alternative birthstone for December, a decision that highlighted the evolving nature of gemological tradition and the global appreciation for new, spectacular minerals.
While the provided sources do not detail specific ancient myths or legends for zircon and tanzanite, the consistent mention of turquoise's association with good fortune and success across historical contexts underscores its enduring cultural significance. This trio of gems, therefore, represents a blend of ancient tradition and modern discovery, each contributing to the symbolic landscape of December.
Geological Formation and Sources
Understanding the origins of these gemstones reveals the remarkable geological processes that create such beauty. Each of the December birthstones forms under distinct conditions and is sourced from specific regions of the world.
Turquoise is a secondary mineral, meaning it forms in the near-surface environment through the interaction of water-rich solutions with pre-existing rocks. It is a hydrous phosphate of copper and aluminum, typically found in arid regions where groundwater can percolate through copper-bearing rocks. The most famous sources include the southwestern United States (particularly Arizona and New Mexico), Iran (known for its historically prized "Persian turquoise"), and Egypt. The color of turquoise ranges from sky blue to greenish-blue, primarily influenced by the presence of copper (blue) and iron (green). Its matrix—the host rock in which it forms—can create distinctive patterns, such as the "spiderweb" matrix prized in some varieties.
Zircon is a zirconium silicate (ZrSiO₄) and is a primary mineral, meaning it crystallizes directly from magma. It is commonly found in igneous and metamorphic rocks. Significant sources include Australia, which produces a wide range of colors; Cambodia, known for its golden-brown "hyacinth" zircon; and Myanmar. Zircon is also found in alluvial deposits (riverbeds and coastal areas) where the hard, durable crystals have been eroded from their original host rock and concentrated. This gemstone is known for its high refractive index and strong dispersion, giving it exceptional brilliance and fire.
Tanzanite is a variety of the mineral zoisite. Its formation is geologically unique. It is found only in a single, small mining area in the Merelani Hills of northern Tanzania, near the foothills of Mount Kilimanjaro. Tanzanite forms when specific geological conditions—high heat and pressure acting on the rock—cause the mineral zoisite to be infused with vanadium, which imparts its signature blue-to-violet color. The scarcity of these conditions makes tanzanite one of the most geographically limited gemstones in the world, contributing to its value and rarity.
The following table summarizes the key sources and geological characteristics of the December birthstones:
| Gemstone | Primary Chemical Composition | Typical Sources | Geological Formation |
|---|---|---|---|
| Turquoise | Hydrous Copper Aluminum Phosphate (CuAl₆(PO₄)₄(OH)₈·4H₂O) | Iran, USA (Arizona, New Mexico), Egypt, Tibet | Secondary mineral formed in arid, near-surface environments through interaction of water with copper-bearing rocks. |
| Zircon | Zirconium Silicate (ZrSiO₄) | Australia, Cambodia, Myanmar, Sri Lanka | Primary mineral crystallizing from magma in igneous and metamorphic rocks; also found in alluvial deposits. |
| Tanzanite | Calcium Aluminum Silicate (Ca₂Al₃(SiO₄)₃(OH)) with Vanadium | Tanzania (Merelani Hills) | Unique metamorphic formation; a variety of zoisite altered by heat and vanadium under specific geological conditions. |
Gemological Properties
The value and durability of a gemstone are determined by its physical and optical properties. The December birthstones exhibit a wide range of these characteristics, which inform their use in jewelry and care requirements.
Turquoise is relatively soft compared to other gemstones, with a Mohs hardness of 5 to 6. This makes it susceptible to scratching and requires careful handling. It has a waxy to vitreous luster and is typically opaque, though some high-quality specimens can be translucent. Its specific gravity ranges from 2.6 to 2.9. A key characteristic of turquoise is its porosity; it can absorb oils and liquids, which can alter its color over time. Stabilization processes, where the stone is impregnated with a clear resin, are commonly used to enhance its durability and color consistency.
Zircon is one of the hardest natural gemstones, with a Mohs hardness of 7.5, making it durable enough for everyday wear in jewelry. It has a high refractive index (1.92-2.01), which is higher than that of diamond (2.42), contributing to its exceptional brilliance. Its strong dispersion (0.039) gives it a fiery, colorful sparkle similar to diamond. Zircon comes in a variety of colors, including colorless, blue, green, yellow, brown, and red. Blue zircon, a popular December birthstone, is often heat-treated to achieve its vibrant blue hue from brownish original crystals.
Tanzanite has a Mohs hardness of 6.5 to 7, making it moderately durable but more susceptible to chipping than harder stones like sapphire. It exhibits strong trichroism, meaning it can display three different colors (typically blue, violet, and burgundy) depending on the crystal's orientation relative to the viewer. Its refractive index is between 1.69 and 1.70, and it has a vitreous luster. Most tanzanite on the market has been heat-treated to remove brownish overtones and enhance its desirable blue-violet color, a process that is stable and widely accepted in the gem trade.
Symbolism and Metaphysical Beliefs
Beyond their physical properties, gemstones carry rich symbolic meanings, often derived from centuries of cultural tradition and metaphysical belief systems.
Turquoise is perhaps the most symbolically charged of the December stones. As a symbol of good fortune and success, it has been universally regarded as a protective talisman. Ancient Persians believed it warded off the "evil eye" and brought blessings. For many Native American cultures, it represents the sky and water, embodying life, health, and spiritual protection. It is often called the "sky stone" or "stone of the earth." Its association with communication and emotional balance is also prevalent in modern crystal healing practices.
Zircon, with its dazzling fire and clarity, is traditionally associated with wisdom, honor, and purity. It is believed to aid in spiritual growth and promote a sense of self-confidence. The colorless variety is linked to clarity of thought, while blue zircon is thought to encourage peace and tranquility. Its historical use as a diamond simulant also ties it to themes of wealth and status, though its own merits as a gemstone of brilliance are now fully recognized.
Tanzanite, as a modern discovery, carries symbolism aligned with its unique origin and appearance. It is often associated with transformation, intuition, and higher consciousness. Its location near the majestic Mount Kilimanjaro lends it an aura of majesty and spiritual elevation. Metaphysically, tanzanite is believed to facilitate communication with the spiritual realm and to stimulate the throat and third-eye chakras, enhancing one's ability to express truth and perceive deeper realities.
It is important to note that while these metaphysical beliefs are widespread in popular culture, they are not scientifically validated. Their significance lies in the cultural and personal meaning individuals ascribe to these beautiful natural minerals.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of December's birthstones, with requirements varying significantly based on their individual properties.
Turquoise requires the most careful handling due to its porosity and relative softness. It should be protected from chemicals, cosmetics, and prolonged exposure to sunlight or heat, which can cause fading or cracking. Cleaning should be done with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and harsh soaps. If necessary, use a mild detergent and lukewarm water, and dry immediately and thoroughly. Store turquoise jewelry separately to prevent scratching.
Zircon is durable but can be brittle due to its crystal structure. It is susceptible to chipping if struck with force, so it is best suited for protective settings like bezels for rings. Cleaning is relatively straightforward: use warm, soapy water and a soft brush. Avoid sudden temperature changes, as zircon can be damaged by thermal shock. Ultrasonic cleaners are generally safe, but steam cleaning is not recommended.
Tanzanite is relatively soft and has perfect cleavage in one direction, making it prone to splitting if struck. It is best worn in earrings, pendants, or bracelets rather than rings for daily wear. Cleaning should be done with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaners, as the vibrations and heat can cause damage. Always remove tanzanite jewelry before physical activities.
Conclusion
The birthstones of December—turquoise, zircon, and tanzanite—offer a fascinating spectrum of geological wonder, historical depth, and cultural symbolism. From the ancient, protective turquoise to the brilliant, fiery zircon and the modern, transformative tanzanite, each gemstone tells a unique story. They are united by their association with the month of December, a time of celebration, reflection, and the enduring promise of light in the darkness of winter. For those born in this month, these stones provide a personal connection to the natural world's artistry and the timeless human quest for meaning, beauty, and good fortune.