December is a unique month in the gemological calendar, distinguished by its official association with three distinct and celebrated birthstones: Turquoise, Tanzanite, and Zircon. This multiplicity offers those born in the final month of the year a rich spectrum of choice, from the ancient, opaque blue-green of Turquoise to the vibrant, violet-blue of Tanzanite and the brilliant, multifaceted blues of Zircon. Beyond these three, Blue Topaz is also recognized as a significant alternative. These gemstones, each with its own unique geological story, physical characteristics, and cultural legacy, collectively define the cool, serene, and festive color palette of winter. This guide delves into the history, origins, gemological properties, and symbolism of December's birthstones, providing a comprehensive resource for enthusiasts, collectors, and anyone captivated by the beauty of these remarkable gems.
The journey into the world of December's birthstones reveals a fascinating convergence of science, history, and lore. While Turquoise has been cherished for millennia, Tanzanite is a relatively modern discovery of the 20th century, and Zircon boasts a history that stretches back to antiquity yet shines with a contemporary brilliance. Understanding the distinct qualities of each stone—from their hardness and durability to their unique optical effects—is essential for appreciating their value and ensuring their preservation. This article will explore these facets in detail, beginning with the rich historical tapestry woven around these gems and moving through their geological origins, defining physical properties, and the cultural meanings they have accumulated over centuries.
History and Lore: A Journey Through Time
The historical significance of December's birthstones is as varied as the gems themselves. Turquoise, in particular, stands as one of the oldest known gemstones in human history, its story extending back thousands of years. Its name provides a direct link to its ancient trade routes; the word "Turquoise" is derived from the French phrase pierre turquoise, meaning "stone of Turkey." This name originated because the gem was brought to Europe from Turkish bazaars, although its source mines were located elsewhere. This nomenclature highlights the intricate network of commerce that moved precious materials across continents in the ancient world. For centuries, Turquoise has been a symbol of success, happiness, and prosperity, deeply embedded in the cultural fabric of numerous civilizations.
In contrast to Turquoise's ancient lineage, Tanzanite is a celebrated newcomer. It is widely regarded as one of the most remarkable gemstone discoveries of the 20th century. Found exclusively in a small, remote area in the foothills of Mount Kilimanjaro in Tanzania, this exotic gem was introduced to the world in the late 1960s. Its sudden appearance and captivating color quickly captured the imagination of the jewelry world, and its designation as a modern birthstone solidified its place in the gemological pantheon. While it lacks the millennia-long history of Turquoise, its rapid rise to prominence speaks to its unique and undeniable beauty.
Zircon, the third official December birthstone, also has a long and sometimes misunderstood history. It is one of the oldest minerals on Earth, with deposits found that date back billions of years. Throughout history, it has been confused with other popular gems, most notably diamond, due to its high refractive index and impressive fire. For much of the 19th and 20th centuries, blue zircon was particularly popular, and its brilliant color made it a frequent substitute for more expensive blue stones. The journey of these three gemstones to their modern status as December's birthstones was solidified by the American National Association of Jewelers (now Jewelers of America), which formalized the list in 1912 and has updated it over the years. This official recognition cemented the trio's role as the definitive gems for those born in the final month of the year.
Geological Formation and Sources
Understanding how and where these gemstones form provides insight into their rarity and unique characteristics. Each of the three official December birthstones has a distinct geological origin.
Turquoise is a secondary mineral that forms in arid or semi-arid regions through a unique geological process. It is not formed from magma deep within the Earth's crust like many other gems. Instead, it is created when water containing copper and aluminum seeps down through the bedrock. Over vast periods, this acidic, copper-rich water reacts with minerals containing phosphorus and aluminum, causing the turquoise mineral to precipitate and fill cracks and voids in the host rock. This process is why turquoise is almost always found in veins or nodules, often interspersed with the host rock, which appears as the distinctive dark lines or "matrix" seen in many turquoise specimens. Major sources for high-quality turquoise include the United States (particularly Arizona and Nevada), Iran, and China.
Tanzanite has an incredibly restricted geographical origin, which is a key factor in its value and allure. It is a variety of the mineral zoisite and is found in only one location on the entire planet: the Merelani Hills of northern Tanzania, near the iconic Mount Kilimanjaro. The geological conditions that created this gem are exceptionally rare. It is believed to have formed from the metamorphism of host rocks under specific temperature and pressure conditions, with the presence of the element vanadium being responsible for its signature violet-blue hue. This single-source origin makes Tanzanite significantly rarer than diamond, and its formation is directly tied to a unique and localized geological event.
Zircon is a mineral composed of zirconium silicate (ZrSiO₄) and is found in a wide variety of geological environments. It is a common accessory mineral in many igneous, metamorphic, and sedimentary rocks. As a detrital mineral, it is highly resistant to weathering and can survive for billions of years, making it a crucial tool for geologists in dating the Earth's oldest rocks. Commercially, significant deposits of gem-quality zircon are found in several countries, including Thailand, Cambodia, Sri Lanka, and Australia. The blue color in blue zircon, the most popular color for December's birthstone, is typically achieved through the heat treatment of brownish zircon, a standard industry practice that enhances the stone's beauty and market appeal.
Gemological Properties: The Science of the Stones
The value and durability of a gemstone are determined by its physical and optical properties. For those considering a December birthstone, understanding these characteristics is critical for both selection and long-term care. The following table summarizes the key gemological data for Turquoise, Tanzanite, and Zircon, as derived from the provided sources.
| Birthstone | Hardness (Mohs Scale) | Specific Gravity | Refractive Index |
|---|---|---|---|
| Turquoise | 5-6 | 2.60-2.90 | 1.61-1.65 |
| Tanzanite | 6.5-7 | 3.10-3.38 | 1.69-1.70 |
| Zircon | 6-7.5 | 3.90-4.73 | 1.93-1.98 |
Turquoise is an opaque mineral, meaning light does not pass through it. Its hardness on the Mohs scale ranges from 5 to 6, making it a relatively soft gem. This softness, combined with its often porous nature, means it is susceptible to scratches and can be damaged by chemicals, cosmetics, and even the natural oils of the skin. Its waxy to vitreous luster gives it a distinctive appearance. The presence of a "matrix"—the host rock remnants visible as a web-like pattern—is a natural characteristic and often adds to the stone's uniqueness and value.
Tanzanite is a transparent to translucent gem with a hardness of 6.5 to 7, making it more durable than Turquoise but still requiring care to avoid scratches and impacts. Its most celebrated and defining optical property is pleochroism. This is the ability of a gemstone to show different colors when viewed from different crystallographic directions. Tanzanite exhibits remarkable trichroism, meaning it can display three distinct colors: blue, violet, and a reddish-burgundy hue, depending on the orientation of the crystal and the viewing angle. Master cutters orient the rough stone to showcase the most desirable blue-violet color in the final faceted gem, making the cut a critical factor in its beauty.
Zircon should not be confused with the synthetic cubic zirconia; it is a natural gemstone with exceptional properties. It possesses a very high refractive index (1.93-1.98), which is higher than that of a diamond (2.42), giving it a brilliant sparkle and impressive "fire" (the dispersion of light into spectral colors). Its hardness varies from 6 to 7.5, making it fairly durable, though it can be brittle due to its crystal structure. Like Tanzanite, Zircon's color can be enhanced by heat treatment, which is used to transform brownish zircon into the brilliant blues that are so popular for December's birthstone.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been imbued with symbolic meanings and metaphysical powers. December's birthstones are no exception, each carrying a legacy of beliefs and attributes.
Turquoise has long been regarded as a stone of protection, wisdom, and good fortune. Many ancient cultures, including the Egyptians, Persians, and Native American tribes, believed it possessed the power to ward off evil and protect the wearer from harm. It was often used as a talisman for travelers and warriors. Its association with success, happiness, and prosperity makes it a popular gift for marking significant life events. The stone is also linked to tranquility and emotional balance, thought to soothe the mind and spirit.
Tanzanite, being a modern discovery, has developed a more contemporary set of symbolic meanings. It is often associated with transformation, intuition, and spiritual awakening. Its unique trichroic nature, revealing different facets of its personality from different angles, is seen as a metaphor for the complexity of human perception and the importance of seeing all sides of a situation. It is considered a stone of higher consciousness, believed to facilitate a connection with one's spiritual guides and to promote a calm, meditative state.
Zircon has a long-standing reputation as a stone of virtue and purity. It was believed to promote honor and prosperity in the home of its wearer. In the Middle Ages, it was used as a protective amulet against poison and plague and was thought to induce sleep and drive away evil spirits. Blue Zircon, in particular, is associated with clarity, focus, and confidence, making it a popular stone for those seeking to achieve their goals and overcome obstacles.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone jewelry. Due to their differing physical properties, the cleaning and handling requirements for December's birthstones vary significantly.
Turquoise requires the most gentle care. Its porosity and relatively low hardness make it vulnerable to damage. It should be cleaned with a soft, dry cloth. Avoid using any chemicals, including mild soap, as well as ultrasonic cleaners and steam cleaners. Prolonged exposure to direct sunlight, heat, or cosmetics can cause the stone to discolor or become brittle over time. It is best to put turquoise jewelry on after applying lotions and makeup.
Tanzanite, while harder than Turquoise, is still somewhat sensitive due to its cleavage properties (a tendency to split along certain planes). It is generally safe to clean with warm water, a mild soap, and a soft brush. However, it is best to avoid ultrasonic cleaners and extreme temperature changes, which could potentially damage the stone. As with most gems, it should be stored separately to prevent scratching.
Zircon, despite its hardness, is brittle. It can be chipped or abraded if knocked against a hard surface. Therefore, it is important to handle it with care. Cleaning can be done with warm, soapy water and a soft brush. It is advisable to avoid ultrasonic cleaners, especially if the stone has been fracture-filled, which is rare for gem-quality zircon but possible. Sudden temperature changes should also be avoided.
Conclusion
The birthstones of December—Turquoise, Tanzanite, and Zircon—offer a remarkable diversity of color, history, and character. From the ancient, protective heritage of Turquoise to the modern, transformative allure of Tanzanite and the brilliant, fiery sparkle of Zircon, each gem provides a unique connection to the natural world and the month of December. Their distinct gemological properties, from the opaque beauty of Turquoise to the mesmerizing pleochroism of Tanzanite and the high refractive index of Zircon, underscore the incredible variety found within the world of colored gemstones. By understanding their origins, symbolic meanings, and care requirements, one can fully appreciate the enduring significance and profound beauty of these winter gems, making them a meaningful and lasting treasure for anyone born in this final, festive month.