Introduction
The final month of the year is distinguished by an exceptionally diverse and historically significant collection of birthstones. Unlike months with a single primary gem, December offers a vibrant palette of colors and lore, primarily centered around Turquoise, Zircon, and Tanzanite. These stones represent a spectrum of geological wonders, from ancient amulets prized by empires to modern discoveries celebrated for their unique brilliance. The choice of a birthstone for those born in December is not merely a matter of color preference but an entry into a rich history that spans continents and cultures. This guide delves into the gemological properties, storied pasts, and cultural symbolism of December's key birthstones, providing a comprehensive resource for enthusiasts, collectors, and anyone captivated by the allure of these remarkable gems.
The Historical Tapestry of December's Birthstones
The modern list of birthstones is a relatively recent standardization, but its roots are deeply embedded in ancient traditions. The concept of a specific gem for each month is often traced back to the Breastplate of Aaron, a ceremonial garment described in the Old Testament, which was set with twelve stones representing the tribes of Israel. Over centuries, various religious and commercial traditions evolved, culminating in the 1912 list by the National Association of Jewelers (NAJ), which established the foundation for today's most widely accepted birthstones. For December, this list has seen additions and variations, reflecting the discovery of new gems and the enduring appeal of ancient ones.
Turquoise: The Ancient Amulet
Turquoise stands as one of the oldest and most culturally significant gems in human history. Its name derives from the French expression pierre tourques, or "Turkish stone," a reference to the gem's introduction to Europe through Turkish markets. However, its origins lie much further east. Sources indicate that Turquoise was originally sourced from Persia (modern-day Iran) and the Sinai Peninsula. For millennia, it was a favored material for amulets and talismans, valued not only for its striking sky-blue to greenish-blue color but also for its relative softness, which made it easy to carve and inscribe.
The cultural reverence for Turquoise is widespread. In Tibet, the stone was considered a birthstone of fortune, health, and success, so valuable that it was often used as currency. Ancient Incas and Mayas offered turquoise to their gods, while Native American tribes of the American Southwest associated it with youth and strength. Beyond its ornamental value, Turquoise was believed to possess powerful protective qualities. It was thought to safeguard its wearer from danger and bring good fortune. Lore suggests that the stone would change color to warn of impending illness or danger, acting as a health monitor for its owner. For lovers, it was a gem of commitment, believed to protect relationships and preserve friendship if given as a gift. This rich tapestry of belief cemented Turquoise's status as a gem of profound spiritual and practical importance.
Zircon: The Stone of Royalty and Misunderstanding
Zircon is one of the oldest minerals on Earth, with deposits found in Australia that date back over 4.4 billion years. Despite its ancient origins, it has often been confused with cheaper, synthetic materials. The most prized variety of Zircon is the hyacinth, a warm, golden-brown to reddish-brown stone that was highly valued in medieval Europe. It was a favorite of clergy and royalty, who believed it brought wisdom, prosperity, and honor. Like Turquoise, Zircon was also thought to have protective properties, inducing sleep and warding off evil spirits. Its high refractive index and strong dispersion (fire) give it a brilliant sparkle that rivals that of a diamond, making it a spectacular gem for jewelry, though it requires careful handling due to its relative brittleness.
Tanzanite: The Modern Marvel
In stark contrast to the ancient history of Turquoise and Zircon, Tanzanite is a very recent addition to the gem world. Discovered in the Merelani Hills of Tanzania in 1967, this vivid blue-to-violet variety of the mineral zoisite was quickly recognized for its extraordinary beauty. Its popularity was propelled by the international jewelry company Tiffany & Co., which named it after its country of origin and made it the centerpiece of its marketing campaigns in the 1970s. Tanzanite's allure lies in its trichroic nature, displaying three distinct colors—blue, violet, and red—depending on the viewing angle. As a relatively soft and more affordable alternative to sapphire, it rapidly became a beloved modern birthstone for December, representing a new era in gemology.
Geological Formation and Mining Locations
The formation of December's birthstones showcases a remarkable diversity of geological processes. Each stone originates under unique conditions, leading to its distinct chemical composition and physical properties.
Turquoise is a secondary mineral that forms when acidic, copper-rich water percolates through pre-existing rocks containing aluminum and phosphorus. This process typically occurs in arid regions, where the evaporation of the water leaves behind deposits of copper aluminum phosphate. The most famous historical sources are in Persia (Iran), which produced the highly prized "robin's egg blue" turquoise, and the Sinai Peninsula. In the United States, significant deposits are found in Arizona, New Mexico, and Nevada, which have been mined by Native American peoples for centuries and continue to produce gem-quality material today.
Zircon is a mineral belonging to the nesosilicate group and is found in igneous, metamorphic, and sedimentary rocks. It is a primary component of granitic and rhyolitic magmas. As these magmas cool, zircon crystals form and are often concentrated in placer deposits through weathering and erosion. Major sources include Australia, which is the leading producer of zircon globally, as well as Thailand, Sri Lanka, and Cambodia. The brownish-red "hyacinth" variety is less common than the colorless or other colored zircons found in these regions.
Tanzanite is a variety of zoisite and is found in only one location in the world: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. Its formation is unique; it is believed to have been created by a massive geological event involving heat and pressure that altered the parent rock, allowing the formation of these blue-violet crystals. Due to its extremely limited geographic source, tanzanite is considered 1,000 times rarer than diamond, adding to its value and allure.
Gemological Properties: A Comparative Analysis
Understanding the physical and chemical properties of a gemstone is crucial for both identification and care. The following table compares the key gemological characteristics of the primary December birthstones based on information from the provided sources.
| Gemstone | Mineral Family | Chemical Formula | Mohs Hardness | Luster | Key Properties & Color |
|---|---|---|---|---|---|
| Turquoise | Phosphate | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | Waxy to Subvitreous | Opaque to semi-translucent; sky-blue to greenish-blue. Porous, often treated with wax or resin. |
| Zircon | Nesosilicate | ZrSiO₄ | 6.5 - 7.5 | Adamantine to Submetallic | High refractive index and strong dispersion ("fire"). Can be heat-treated to a colorless or blue color. |
| Tanzanite | Sorosilicate | Ca₂Al₃(SiO₄)₃(OH) | 6 - 6.5 | Vitreous to Pearly | Trichroic (blue, violet, red). Typically heat-treated to enhance blue color. Relatively soft. |
| Blue Topaz | Silicate | Al₂SiO₄(F,OH) | 8 | Vitreous | Often treated to achieve blue color. High durability, but can be brittle due to cleavage. |
Color, Clarity, and Cut
The color of a gemstone is its most defining characteristic. For Turquoise, the most prized color is an even, medium to light "robin's egg blue." Its color is derived from copper, and it is often found with a characteristic matrix (a web of darker host rock). Turquoise is typically opaque, and its clarity is not graded in the same way as transparent stones. It is often cut into cabochons, beads, and carved shapes.
Zircon occurs in a wide range of colors, but the golden-brown "hyacinth" is its traditional birthstone color. It is also found in blue, green, yellow, orange, and red. Blue zircon is often the result of heat treatment of brown zircon. Zircon is generally transparent and is valued for its high clarity. Its exceptional brilliance makes it ideal for faceted cuts, which maximize its light performance.
Tanzanite is known for its saturated violet-blue to deep blue color. Its signature feature is its trichroism, where a single crystal can show three different colors: blue, violet, and a reddish-brown or burgundy hue when viewed from different directions. Gem cutters must orient the crystal carefully to present the most desirable blue-violet face-up color. Tanzanite is typically transparent and is almost always cut with facets to enhance its brilliance.
Durability and Wearability
Durability is a key factor in choosing jewelry, especially for pieces worn daily. The Mohs hardness scale is a standard measure of a mineral's resistance to scratching.
- Turquoise has a hardness of 5 to 6. This makes it relatively soft and susceptible to scratching and damage from chemicals, cosmetics, and heat. It is porous and can absorb oils and liquids, which may alter its color over time. Turquoise jewelry is best suited for occasional wear or pieces like pendants and earrings that are less prone to impact.
- Zircon has a hardness of 6.5 to 7.5, making it fairly durable. However, it can be brittle and is prone to chipping if struck against a hard surface. Its cleavage (a tendency to break along flat planes) requires that it be set and handled with care.
- Tanzanite has a hardness of 6 to 6.5, making it softer than many other gems used in rings. It is not recommended for daily-wear rings unless it is set in a protective mounting.
- Blue Topaz, mentioned as a modern alternative, has a hardness of 8, making it highly durable and suitable for all types of jewelry. However, it can also have perfect cleavage, making it susceptible to chipping from sharp impacts.
Symbolism and Metaphysical Beliefs
Across cultures and centuries, gemstones have been imbued with symbolic meanings and metaphysical powers. December's birthstones are particularly rich in such lore.
Turquoise is perhaps the most spiritually significant of the group. It has been universally regarded as a stone of protection, healing, and good fortune. Its connection to the sky and water made it a symbol of life and fertility in many ancient cultures. The belief that it could change color to warn its owner of danger or illness highlights its role as a vigilant guardian. For the Tibetan people, it was a stone of success and well-being, while for Native Americans, it embodied the life-giving forces of the sky and water.
Zircon has long been associated with wisdom, honor, and prosperity. It was believed to help its owner achieve a clear mind and make wise decisions. In some traditions, it was said to promote sleep and ward off nightmares, acting as a protective talisman during the night. Its brilliance was seen as a reflection of inner light and clarity.
Tanzanite, as a new discovery, has been assigned more contemporary metaphysical meanings. It is often associated with transformation, intuition, and spiritual awakening. Its unique trichroic nature is seen as a metaphor for seeing the world from multiple perspectives and achieving a higher state of consciousness. It is also considered a stone of communication, helping to articulate spiritual truths.
Care and Cleaning
Proper care is essential to preserve the beauty and longevity of gemstone jewelry. The diverse properties of December's birthstones demand specific attention.
Turquoise is the most delicate of the group and requires gentle handling. It should be cleaned with a soft, dry cloth. Avoid using warm soapy water, as it can be absorbed into the stone, potentially altering its color or causing the wax used to fill pores to lift. Chemicals found in cosmetics, hairspray, and perfume can damage the stone and should be avoided.
Zircon is relatively hard but can be brittle. It is best cleaned with warm water, a mild soap, and a soft brush. Ultrasonic and steam cleaners are not recommended, as the vibrations and heat could potentially damage the stone, especially if it has been fracture-filled or has existing inclusions.
Tanzanite should be cleaned gently with warm, soapy water and a soft brush. It is not recommended for ultrasonic cleaners or steam cleaning, as it is sensitive to heat and vibrations. Due to its relative softness, it should be stored carefully to avoid scratches from harder gems. Jewelry containing Tanzanite should be the last thing you put on and the first thing you take off, avoiding contact with lotions, makeup, and perfumes.
Conclusion
The birthstones of December offer a compelling journey through geological time, human history, and cultural expression. From the ancient, protective amulet of Turquoise, cherished from Persia to the Americas, to the brilliant, royal Zircon, and the modern, transformative discovery of Tanzanite, each gem tells a unique story. Their colors range from the serene sky-blue of turquoise to the fiery sparkle of zircon and the deep, trichroic blues of tanzanite, providing a wealth of choices for those born in the final month of the year. Understanding their origins, properties, and symbolism not only enhances their beauty but also deepens the connection between the wearer and the remarkable natural world from which they came. Whether chosen for its lore, its durability, or its sheer visual appeal, a December birthstone is a timeless treasure.