For those born in the final month of the year, the choice of a birthstone is not a simple one. Unlike most months, which are associated with a single gem, December offers a rich palette of four distinct blue stones: Turquoise, Zircon, Tanzanite, and Blue Topaz. This abundance provides a spectrum of color, from the sky-blue of turquoise to the deep indigo of London Blue Topaz and the vibrant violet-blue of Tanzanite. Each of these gems carries a unique geological origin, a storied history, and a set of gemological properties that make it a compelling choice for jewelry and collection. This guide explores the science, history, and symbolism behind December's four celebrated birthstones.
A Spectrum of Blue: The Four Gems of December
The modern association of four birthstones with December is a departure from historical tradition, offering consumers greater variety in color, durability, and price. The official birthstones recognized by the Gemological Institute of America (GIA) are Turquoise, Tanzanite, and Zircon, with Blue Topaz having gained significant popularity as a modern alternative. All four stones are celebrated for their captivating blue hues, though their origins and characteristics are vastly different.
Turquoise is perhaps the most ancient of the group, an opaque gem ranging from soft sky blue to greenish hues, often distinguished by its characteristic matrix—the remnants of the host rock that form spiderweb-like veins within the stone. Its color is a result of copper and aluminum minerals.
Zircon should not be confused with the synthetic cubic zirconia; it is a natural gemstone prized for its exceptional brilliance and fire, often mistaken for a diamond. The blue variety, which is the birthstone for December, is typically achieved through heat treatment of brownish zircon.
Tanzanite is a relative newcomer to the gem world, discovered in the 20th century. It is celebrated for its rich violet-blue color, which can appear differently under various light sources, a phenomenon known as pleochroism. Its color is the result of vanadium and other trace elements.
Blue Topaz is a popular modern choice, known for its clear, glassy luster and a range of blue shades from light sky blue to the deep, inky tones of London Blue Topaz. It is important to note that naturally occurring blue topaz is exceptionally rare; the vast majority of blue topaz on the market is produced by irradiating and heat-treating colorless topaz.
History and Lore: From Ancient Amulets to Modern Marvels
Each of December's birthstones is steeped in a rich tapestry of history and cultural significance, reflecting centuries of human fascination with the color blue.
Turquoise: The Ancient Protector Turquoise is one of the oldest known gemstones in human history, cherished for millennia. Ancient Egyptians adorned themselves with turquoise jewelry; pharaohs and other rulers were buried with this gem, believing it offered protection in the afterlife. The famous burial mask of Tutankhamun is heavily inlaid with turquoise. In China, artisans were carving turquoise more than 3,000 years ago.
The turquoise birthstone was thought to possess many beneficial powers, like guaranteeing health and good fortune. From the 13th century onward, it was widely believed to protect the wearer from falls, particularly from horses, and would shatter into several pieces at the approach of disaster, serving as a warning. Hindu mystics maintained that seeing a turquoise after beholding the new moon would ensure fantastic wealth. For Native Americans, particularly the Apache, the stone held deep spiritual significance. They believed turquoise could be found by following a rainbow to its end and that it offered protection and connection to the natural world. The Pueblo also attributed healing properties to the stone.
Zircon: The Gem of Wisdom and Honor Zircon has a long history of use as a gemstone, though its name is often confused with cubic zirconia. For centuries, zircon was regarded as a stone of honor and wisdom. In the Middle Ages, it was believed to bring prosperity to its wearer and to ward off evil spirits. Its high refractive index and brilliance made it a popular diamond simulant, and it was often used in royal jewelry. The blue variety, in particular, has been valued for its resemblance to the highly coveted sapphire.
Tanzanite: The Blue Miracle of the 20th Century Tanzanite's history is remarkably short but dramatic. It was discovered by Manuel de Souza in the Merelani Hills of northern Tanzania in 1967. Initially, prospectors dismissed the blue crystals as worthless, but once its gemological properties were recognized, its popularity soared. The gemstone was named "tanzanite" by Tiffany & Co., which introduced it to the world in 1968 and promoted it heavily as a "blue miracle" found in only one location on Earth. Its color is a unique violet-blue that is not found in any other gemstone, making it highly sought after. It is often associated with a modern sense of style and transformation.
Blue Topaz: The Modern Favorite While topaz itself has been known since antiquity, with the name deriving from the Sanskrit word for "fire," its blue variety has become a staple of the modern jewelry market. Historically, topaz was associated with strength and protection. The modern association of blue topaz with December is a relatively recent development, driven by consumer demand for a durable, affordable, and brilliantly blue gemstone. Its rise in popularity is linked to the development of treatments that can transform colorless topaz into the vibrant blue hues desired by the market.
Geological Formation and Sources
Understanding where these gems come from adds another layer of appreciation for their rarity and beauty.
Turquoise is a secondary mineral that forms when water containing copper and aluminum seeps through rocks. This process occurs in arid regions, and its primary sources are in the United States (especially Arizona, New Mexico, and Nevada), Iran, and China. The specific geology of a region determines the color and matrix pattern of the turquoise.
Zircon is one of the oldest minerals on Earth, found in the crust of the planet. It forms as crystals in igneous and metamorphic rocks. Significant sources for gem-quality zircon include Australia, Cambodia, Sri Lanka, and Thailand. The blue color in most birthstone-grade zircon is achieved by heating brownish zircon at high temperatures in a controlled environment.
Tanzanite is found in only one location in the world: the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. Its formation is a geological anomaly, occurring when specific minerals were subjected to intense heat and pressure during the formation of the East African Rift Valley. This singular source contributes to its value and allure.
Blue Topaz crystals are typically found in granitic pegmatites and hydrothermal veins. While topaz occurs in many locations globally, including Brazil, Russia, and the United States, the material suitable for treatment into the deep blue shades of London Blue Topaz often comes from Brazil. The United States also has notable sources; for example, Blue Topaz is the state gem of Texas.
Gemological Properties: A Scientific Comparison
A gemstone's durability, appearance, and value are determined by its physical and chemical properties. The following table compares key gemological characteristics of December's birthstones. Data is compiled from gemological sources.
| Gemstone | Chemical Composition | Mohs Hardness | Crystal System | Key Properties |
|---|---|---|---|---|
| Turquoise | Hydrated phosphate of copper and aluminum (CuAl₆(PO₄)₄(OH)₈·4H₂O) | 5 - 6 | Triclinic | Opaque, waxy luster, porous. Color ranges from blue to green with matrix. |
| Zircon | Zirconium silicate (ZrSiO₄) | 6.5 - 7.5 | Tetragonal | High refractive index and dispersion ("fire"). Can be brittle due to cleavage. |
| Tanzanite | Calcium aluminum hydroxyl sorosilicate (Ca₂Al₃(SiO₄)₃(OH)) | 6.5 - 7 | Orthorhombic | Strong pleochroism (displays different colors from different angles). |
| Blue Topaz | Aluminum fluorosilicate (Al₂SiO₄(F,OH)₂) | 8 | Orthorhombic | Glass-like luster. Brittle due to deep cleavage. Most blue is treated. |
Hardness and Durability: On the Mohs scale of hardness, Blue Topaz is the most durable at 8, making it resistant to scratching for everyday wear. However, it has perfect cleavage in one direction, meaning it can be chipped or broken by a sharp blow. Zircon and Tanzanite have a hardness of 6.5 to 7.5 and 6.5 to 7, respectively, making them moderately durable but also susceptible to chipping due to cleavage planes. Turquoise, with a hardness of 5 to 6, is the softest and most porous of the four. It is more delicate and requires careful handling to avoid scratches, dents, and chemical exposure that can damage its color.
Color and Clarity: The color of each stone is its defining feature. Turquoise is prized for its opaque, uniform color, though the matrix is a key part of its character. Zircon is known for its brilliance and clarity, with the blue variety ranging from bright to deep tones. Tanzanite's unique violet-blue and its pleochroism make it a fascinating gem for cutters and collectors. Blue Topaz offers a wide range of consistent, saturated blues, from the pale Sky Blue to the deep, inky London Blue.
Symbolism and Metaphysical Beliefs
Across cultures, these blue stones have been attributed with powerful symbolic meanings and metaphysical properties.
- Turquoise is universally regarded as a stone of protection, good fortune, and healing. It is believed to calm the mind, soothe emotions, and shield the wearer from negative energy. Its connection to the sky and water in many cultures reinforces its symbolism of tranquility and life.
- Zircon is associated with wisdom, clarity, and honor. It is said to promote spiritual growth and help its wearer achieve a sense of balance and stability. Its brilliant sparkle is thought to inspire confidence and self-esteem.
- Tanzanite, as a relatively new gem, has modern metaphysical associations centered on transformation, new beginnings, and higher consciousness. It is believed to facilitate a connection between the heart and the mind, encouraging a calm, centered state.
- Blue Topaz is linked to calmness, love, and clarity. It is often considered a stone of communication, helping to express one's thoughts and feelings clearly and compassionately. Its serene blue color is thought to promote relaxation and stress relief.
Care and Cleaning: Preserving Your Gemstone
Proper care is essential to maintain the beauty and longevity of December's birthstones, given their varying levels of durability.
- Turquoise: Due to its porosity, turquoise is sensitive to chemicals, including cosmetics, perfumes, and even the oils in skin. It should be cleaned with warm, soapy water and a soft cloth. Avoid ultrasonic cleaners and steam cleaning. Store it separately to prevent scratching.
- Zircon: While fairly hard, zircon can be brittle. It is best cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and extreme temperature changes, which can cause the stone to crack.
- Tanzanite: This gem is relatively soft and has perfect cleavage, making it vulnerable to knocks and temperature shocks. Clean with warm, soapy water and a soft brush. It is not recommended for rings worn daily unless set in a protective mounting. Avoid ultrasonic and steam cleaners.
- Blue Topaz: Although hard, its cleavage makes it susceptible to chipping. It is generally safe to use warm, soapy water and a soft brush for cleaning. However, avoid ultrasonic cleaners if the stone has been fracture-filled (which is rare for topaz, but possible). As a treated stone, prolonged exposure to strong heat or light could potentially alter its color, though this is unlikely under normal conditions.
Conclusion
December's birthstones offer a remarkable diversity that sets them apart. From the ancient, protective talisman of Turquoise to the brilliant, diamond-like fire of Zircon, the singular, transformative discovery of Tanzanite, and the modern, accessible allure of Blue Topaz, each gem provides a unique story and aesthetic. Their shared blue color connects them to the winter sky and sea, yet their individual histories, from the tombs of pharaohs to the mines of Tanzania, give them distinct personalities. For anyone born in December, the choice is not merely a matter of preference in color, but an opportunity to connect with a specific piece of the Earth's geological and cultural heritage.