For those born in the final month of the year, the birthstone palette is a celebration of blue. Unlike months with a single designated gem, December offers a remarkable collection of four distinct blue stones: the ancient Turquoise, the modern Tanzanite, the brilliant Zircon, and the popular Blue Topaz. Each gem possesses a unique geological origin, a rich history, and a set of gemological properties that set it apart. This variety provides December-born individuals a spectrum of choices, from the earthy, opaque tones of turquoise to the fiery brilliance of zircon. This guide delves into the science, history, and symbolism of these four magnificent blue birthstones, offering a comprehensive resource for gemstone enthusiasts, collectors, and anyone seeking to understand the gems of December.
A Rich History and Diverse Lore
The story of December's birthstones spans millennia, connecting ancient civilizations with modern luxury. The most traditional of these gems, Turquoise, is one of the oldest known to humanity. Its name is a testament to its long journey into Western culture; it derives from the French phrase pierre turquoise, meaning "Turkish stone." This name was given because the gem was first brought to Europe through Turkish bazaars, though its origins lie elsewhere. Historical evidence shows that turquoise has been treasured for thousands of years, adorning everyone from ancient Egyptian pharaohs to Native American chiefs. It was not merely an ornament but a powerful talisman, long considered a symbol of protection, wisdom, and good fortune. Ancient beliefs held that the stone could warn its wearer of impending danger by cracking or changing its color, making it a trusted companion in uncertain times.
In stark contrast to the ancient lineage of turquoise is Tanzanite, the newest addition to the December family. This velvety blue-violet gem was first unearthed in 1967 in the Merelani foothills of Mount Kilimanjaro in Tanzania. Its discovery is a distinctly modern event, and its fame was swiftly propelled by the renowned jewelry house Tiffany & Co., which recognized its unique beauty and began featuring it prominently in their designs. The gem's allure lies in its pleochroism—the ability to display different colors when viewed from different angles. In certain lighting, it can shift from a deep, rich blue to a vibrant violet, a characteristic that adds to its mystique and desirability.
Zircon, another of December's official birthstones, also boasts a history of immense popularity. While not as ancient as turquoise in terms of human use, it has been a favored gem for centuries, particularly during the Victorian era, where its brilliant sparkle was highly sought after for jewelry. Its name is often confused with the synthetic cubic zirconia, but natural zircon is a distinct and far older mineral. This confusion sometimes detracts from its prestige, yet for those in the know, zircon remains a gem of exceptional brilliance and fire.
Blue Topaz is frequently cited as a modern or alternative birthstone for December. While topaz in its natural state occurs in a variety of colors, the vibrant, often electric blues seen in jewelry are typically the result of irradiation and heat treatment of pale or colorless topaz. Its rise as a popular December birthstone is tied to its availability in larger carat sizes and its affordability compared to some of the other blue gems, making it an accessible choice for a wide audience.
Geological Formation and Global Sources
Understanding the origins of these gems reveals the diverse geological processes that create such beautiful variations of the color blue.
Turquoise is unique as it is an opaque mineral, not a crystalline one. It is a hydrous phosphate of copper and aluminum, formed when groundwater containing copper seeps into bedrock. Over immense periods, this water reacts with minerals containing aluminum and phosphorus, depositing turquoise in veins, nodules, and as a coating on the host rock. The presence of copper is what gives turquoise its signature blue to blue-green color. The dark veins and patterns often seen running through the stone are known as the "matrix," which is the remnants of the host rock. This matrix, often brown or black, is derived from the surrounding rock and makes each piece of turquoise as unique as a fingerprint. Major sources for turquoise include Iran (historically Persia), the Southwestern United States (notably Arizona and New Mexico), and China.
Tanzanite is a variety of the mineral zoisite and owes its existence to a unique and singular geological event. It is found in only one location on Earth: the Merelani foothills of Mount Kilimanjaro in Tanzania. Its formation is believed to be the result of a massive tectonic plate shift and subsequent heating event that occurred around 585 million years ago. This event transformed the zoisite crystals into the blue-violet tanzanite we know today, while leaving other parts of the original deposit unchanged. This extreme rarity of location is a major factor in its value and appeal.
Zircon is one of the oldest minerals on Earth, with crystals found in Australia dating back over 4.4 billion years. It is a natural zirconium silicate (ZrSiO₄) that forms in the cracks and cavities of igneous and metamorphic rocks, such as granite and gneiss. While found in many places, the gem-quality crystals used for jewelry come from countries like Cambodia, Sri Lanka, and Thailand. The brilliant "fire" of zircon is a natural property, a result of its high refractive index.
Blue Topaz is a variety of the mineral topaz, which forms in igneous rocks like granite and rhyolite, often in cavities where late-stage, fluorine-rich fluids can crystallize. The natural blue color in topaz is very rare and typically pale. The intense, saturated blues of commercial jewelry are achieved by treating colorless or pale yellow topaz with gamma and neutron radiation, followed by heat treatment. The United States (specifically Texas) and Brazil are notable sources for the colorless topaz that is often treated to become blue topaz.
Gemological Properties: A Comparative Analysis
For students of gemology and discerning buyers, the physical and chemical properties of a gemstone are paramount. Each of the December birthstones has a distinct profile on the Mohs scale of hardness and unique optical characteristics.
Turquoise is the softest of the group, with a hardness of 5 to 6 on the Mohs scale. Its low hardness and occasional porosity make it susceptible to damage from chemicals, heat, and even prolonged exposure to skin oils and lotions, which can alter its color over time. It is an opaque stone with a waxy to vitreous luster.
Tanzanite has a hardness of 6.5 to 7 on the Mohs scale, making it moderately durable but still requiring care. Its most significant property is its strong trichroism, displaying three different colors: blue, violet, and reddish-brown depending on the crystal orientation. Most tanzanite is heat-treated to remove the brownish component and enhance the desirable blue-violet hue.
Zircon is the hardest of the December stones, with a hardness of 6.5 to 7.5. However, it is known for being brittle and having poor toughness due to its cleavage, meaning it can split if struck with sufficient force. Its most celebrated property is its high refractive index (1.92-1.98), which gives it a brilliance and fire that can rival diamond. It is also strongly double-refractive, a property that gem cutters must carefully manage.
Blue Topaz has a hardness of 8 on the Mohs scale, making it the most durable and scratch-resistant of the four, an excellent quality for rings worn daily. It is also strongly doubly refractive and has a vitreous luster. Its clarity is generally good, with clean stones being readily available.
Summary of Gemological Properties
| Gemstone | Mineral Species | Hardness (Mohs) | Chemical Composition | Key Property |
|---|---|---|---|---|
| Turquoise | Phosphate mineral | 5 - 6 | CuAl₆(PO₄)₄(OH)₈·4H₂O | Opaque, often features a matrix |
| Tanzanite | Zoisite | 6.5 - 7 | Ca₂Al₃(SiO₄)₃(OH) | Strong trichroism (blue, violet, red) |
| Zircon | Zirconium Silicate | 6.5 - 7.5 | ZrSiO₄ | High refractive index, strong fire |
| Blue Topaz | Topaz | 8 | Al₂SiO₄(F,OH)₂ | High durability, clarity |
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these stones are deeply imbued with meaning and have been credited with various powers throughout history.
Turquoise is perhaps the most potent in terms of symbolism. It has universally been regarded as a stone of protection, said to guard the wearer against harm and negative energy. It is also linked to wisdom, tranquility, and good fortune. Many cultures believed it could connect the wearer to the spiritual world and promote communication with divine beings.
Tanzanite, as a modern discovery, has been assigned more contemporary metaphysical properties. It is often called the "stone of transformation" and is believed to facilitate a higher consciousness, intuition, and spiritual perception. Its calming energy is said to help overcome sadness and grief.
Zircon has historically been associated with prosperity and honor. It was believed to promote a sound sleep and ward off evil spirits. In the Middle Ages, it was used as a protective amulet for travelers.
Blue Topaz is associated with calm, clarity, and communication. It is considered a stone of love and good fortune, believed to help express one's feelings and promote truth and forgiveness.
Care and Cleaning Recommendations
Proper care is essential to maintain the beauty and longevity of any gemstone. Due to their varying properties, the December birthstones require different handling.
Turquoise: As the most delicate, turquoise should be protected from chemicals, including those in cosmetics, lotions, and even some cleaning agents. It should not be soaked in water or exposed to prolonged sunlight. Cleaning should be done with a soft, dry cloth. Store it separately to avoid scratches from harder stones.
Tanzanite: This gem should be protected from sharp blows and extreme temperature changes, which can cause fracturing. It is best cleaned with warm water, a mild soap, and a soft brush. Ultrasonic and steam cleaners should be avoided.
Zircon: While hard, zircon is brittle and can be easily chipped if knocked against a hard surface. It is also sensitive to heat. Standard warm water and soap cleaning is safe, but ultrasonic cleaners are not recommended. Some older zircon may have been subjected to heat treatment to improve color, and excessive heat could reverse this.
Blue Topaz: Due to its good hardness and stability, blue topaz is relatively easy to care for. It can be cleaned with warm, soapy water and a soft brush. It is generally safe from standard ultrasonic and steam cleaners, though it is always wise to check if the stone has been treated in a way that might make it sensitive.
Conclusion
The birthstones of December offer a diverse and stunning collection that caters to every taste. From the ancient, protective talisman of Turquoise to the singular, transformative allure of Tanzanite, the brilliant fire of Zircon, and the durable, serene beauty of Blue Topaz, each gem tells a unique story. Their differences in hardness, origin, and symbolism provide a rich field for exploration for gem lovers and a wealth of beautiful options for those celebrating a December birthday. Whether chosen for its historical significance, its geological rarity, or simply its captivating shade of blue, a December birthstone is a timeless and meaningful treasure.