Introduction
December stands uniquely distinguished in the calendar of birthstones, offering not one, but three captivating gems for those born in its final month: turquoise, tanzanite, and zircon. This multiplicity provides a rare choice of color and character, from the ancient, opaque sky-blue of turquoise to the modern, pleochromatic brilliance of tanzanite and the fiery sparkle of zircon. Each stone carries its own profound history, geological origin, and set of gemological properties, yet all are united by their vibrant hues that have captured human imagination for millennia. This article delves into the rich tapestry of these three December birthstones, exploring their journey from the earth's depths to the forefront of gemology, their scientific attributes, and the enduring symbolism they hold. We will examine the storied past of turquoise, the recent but meteoric rise of tanzanite, and the often-misunderstood brilliance of zircon, providing a comprehensive guide for enthusiasts, collectors, and anyone drawn to the allure of these remarkable gems.
History and Lore
The historical narratives of December's birthstones are as diverse as their colors, spanning ancient civilizations to modern discoveries.
Turquoise possesses the most ancient pedigree. Its name is derived from the French pierre turquoise, meaning "Turkish stone," reflecting its historical trade route from Persia (modern-day Iran) through Turkey to Europe. For thousands of years, it has been a prized gem in cultures across the globe. Ancient Egyptians adorned themselves with turquoise, believing it offered protection and connection to the divine, as evidenced by the burial goods of Pharaohs. In the American Southwest, Native American tribes have a deep spiritual connection to the stone, viewing it as a piece of the sky and a conduit for communication with spirits. It was one of the first gems to be mined and used in jewelry, and its status as a birthstone is deeply rooted in historical tradition, often associated with the month of December in both the traditional (1912) and modern birthstone lists.
Tanzanite is a product of the modern era. Discovered in the Merelani Hills of Tanzania in the late 1960s, its history is remarkably short but dramatic. Initially, the blue zoisite crystals were overlooked by miners searching for sapphire. However, the exceptional color of this material was soon recognized, and it was given its name by Tiffany & Co. in 1968, who launched it as a new gemstone. The company's marketing campaign, emphasizing its rarity and unique blue-violet hue, was immensely successful. Tanzanite was officially added to the modern birthstone list for December in 2002, making it the newest addition to the birthstone family. Its story is one of serendipity and modern marketing, transforming a local curiosity into a globally celebrated gem.
Zircon has an equally long but more complex history. The term "zircon" may come from the Arabic zarkun, meaning "vermillion" or "gold-colored," though it is now most famous for its blue variety. For centuries, zircon was often confused with cubic zirconia (a synthetic diamond simulant) or other gems like jacinth, leading to some historical confusion. However, natural zircon is one of the oldest minerals on Earth, with some specimens dating back billions of years. In the Middle Ages, it was believed to promote rest, honor, and wisdom. The blue variety, achieved through heat treatment of brownish zircon, became particularly popular in the Victorian era. It is traditionally listed as a birthstone for December, offering a brilliant, diamond-like alternative.
Geological Formation and Sources
The origins of these gems are as varied as their histories, formed under different geological conditions and mined from specific, often limited, locations.
Turquoise is a hydrous phosphate of copper and aluminum, forming in arid regions where acidic water, rich in copper, interacts with aluminum-bearing rocks. This process occurs in near-surface environments, creating nodules, veins, or matrix-filled seams. The most significant historical source is Iran (Persia), known for its "sleeping beauty" turquoise—a pure, sky-blue without matrix. In the United States, the Southwestern states of Arizona, Nevada, and New Mexico are major producers, with mines like the Sleeping Beauty Mine in Arizona and the Bisbee mine in Arizona yielding significant quantities. Other sources include China, Egypt, and Tibet. The quality is often judged by its color, matrix (the host rock), and stability.
Tanzanite is a variety of the mineral zoisite, colored by vanadium. Its formation is exceptionally rare, requiring specific geological conditions that have only been found in a single, small area: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This geographic exclusivity makes tanzanite one of the rarest gemstones known. The mining area is divided into four blocks, with Block C being the most productive. The gem is typically found in elongated, tabular crystals within a host rock of schist and quartzite. Due to its limited source, tanzanite is often considered more valuable per carat than many other colored gems.
Zircon is a zirconium silicate (ZrSiO₄) that crystallizes in igneous and metamorphic rocks. It is a common accessory mineral found in many geological formations worldwide, but gem-quality material is much rarer. Major sources include Sri Lanka (Ceylon), which has historically produced fine blue and golden zircons; Thailand and Cambodia for brown and orange varieties; Australia (particularly New South Wales) for brown zircons; and Vietnam and Myanmar for a range of colors. The blue variety, which is most associated with December, is typically produced by heating brown zircon from Sri Lanka or Cambodia.
Gemological Properties
Understanding the physical and chemical characteristics of each gem is essential for identification, valuation, and care. The following table summarizes key gemological properties of the three December birthstones, based on established data.
| Property | Turquoise | Tanzanite | Zircon |
|---|---|---|---|
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | Ca₂Al₃(SiO₄)₃(OH) | ZrSiO₄ |
| Crystal System | Triclinic | Orthorhombic | Tetragonal |
| Hardness (Mohs) | 5 - 6 | 6.5 - 7 | 6.5 - 7.5 |
| Specific Gravity | 2.60 - 2.90 | 3.35 | 4.60 - 4.70 |
| Refractive Index | 1.610 - 1.650 | 1.690 - 1.700 | 1.920 - 1.980 |
| Key Characteristic | Porosity, often matrix-included | Strong trichroism (blue, violet, burgundy) | High refractive index, brilliance |
Turquoise is a relatively soft and porous gem, which explains its historical use in beads and cabochons rather than faceted stones. Its color ranges from sky blue to greenish blue, influenced by copper (blue) and iron (green) content. The presence of the host rock, or "matrix," is a common feature, especially in American turquoise, and can be black (from iron oxide) or brown (from limonite). Stability is a concern, as untreated turquoise can discolor or crack with exposure to chemicals, heat, or prolonged sunlight.
Tanzanite is known for its intense, saturated blue-to-violet color, which is a result of vanadium impurities. A defining feature is its strong trichroism, meaning it displays three different colors when viewed from different crystal directions: blue, violet, and a reddish-brown or burgundy. Most tanzanite is heated to 500-600°C to remove the brownish component and enhance the blue/violet color, a stable and permanent treatment. It has good hardness but can be susceptible to chipping if cut with thin points or if struck sharply. Its refractive index is moderate, but its color saturation gives it a vibrant appearance.
Zircon is often called the "poor man's diamond" due to its high refractive index and strong dispersion (fire), which gives it a sparkle comparable to diamond. It occurs in a wide range of colors, including blue, golden yellow, brown, red, and green. The blue variety is typically produced by heat-treating brown zircon. Zircon has a high specific gravity, making it feel heavier than a similarly sized diamond or cubic zirconia. It is relatively hard, though it can be brittle and prone to cleavage, requiring careful cutting and setting. Its high refractive index (1.92-1.98) is second only to diamond among natural gems.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each of these gems carries a wealth of symbolic meaning and metaphysical lore, often rooted in their color and historical use.
Turquoise is universally regarded as a stone of protection, healing, and good fortune. Across cultures, it has been believed to ward off negative energy, accidents, and illness. In Persian tradition, it was seen as a bringer of luck and a symbol of divine connection. For Native Americans, it represents the sky and water, embodying life, healing, and spiritual grounding. It is often associated with the throat chakra, believed to aid in honest communication and self-expression. In modern crystal healing, turquoise is used for calming nerves, balancing emotions, and strengthening the immune system.
Tanzanite, as a newer gem, has quickly developed its own set of modern metaphysical associations. It is often called the "stone of transformation" due to its dramatic color change and rarity. It is believed to promote spiritual awakening, higher consciousness, and clear communication. Its trichroic nature is seen as a metaphor for the integration of mind, body, and spirit. Some proponents suggest it stimulates the throat and crown chakras, facilitating a connection to higher realms and intuitive insight. Its calming blue-violet hue is also associated with relieving stress and anxiety.
Zircon has a long history of symbolism tied to its brilliant sparkle. Historically, it was believed to promote honor, purity, and wisdom. It was thought to aid in restful sleep, protect against nightmares, and bring prosperity. The blue variety, in particular, is associated with peace and tranquility. In some traditions, zircon is linked to the root chakra, providing grounding and stability. Its diamond-like fire has also led to associations with clarity of thought and the ability to see the truth in situations.
Care and Cleaning
Proper care is crucial to maintaining the beauty and longevity of these birthstones, with each requiring specific attention due to their distinct physical properties.
Turquoise is the most delicate of the three. Due to its porosity and moderate hardness (5-6), it is susceptible to damage from chemicals, heat, and physical impact. * Cleaning: Use only lukewarm water, a mild soap, and a soft cloth. Avoid ultrasonic cleaners, steam cleaners, and any household chemicals (including perfume, hairspray, and lotions), which can cause discoloration or cracking. Dry thoroughly after cleaning. * Storage: Store separately in a soft pouch to avoid scratches from harder gems. Keep it away from prolonged direct sunlight, which can fade its color.
Tanzanite has a hardness of 6.5-7, making it more durable than turquoise but still requiring care. * Cleaning: It is safe to use warm soapy water and a soft brush. Ultrasonic cleaners are generally not recommended, as the vibrations could cause damage if the stone has inclusions or fractures. Steam cleaning should be avoided due to potential thermal shock. * Storage: As with all gems, store it separately to prevent scratching. Given its value and relative rarity, professional setting is recommended to protect the stone.
Zircon, with a hardness of 6.5-7.5, is relatively durable but has a tendency to cleave (split along internal planes) if struck with force. * Cleaning: Warm soapy water and a soft brush are safe. Avoid ultrasonic cleaners and steam cleaners, as the heat and vibrations can exacerbate any existing internal stresses or fractures. * Storage: Store zircon jewelry carefully, ideally in a fabric-lined box or separate compartment. Avoid wearing it during activities where it might be knocked against hard surfaces.
Conclusion
The trio of December birthstones—turquoise, tanzanite, and zircon—offers a remarkable spectrum of color, history, and character. From the ancient, protective talisman of turquoise to the modern, transformative allure of tanzanite and the brilliant, diamond-like fire of zircon, each gem provides a unique narrative. Their geological origins are as diverse as their stories, from the copper-rich deserts of the American Southwest and the singular deposit in Tanzania to the crystalline formations found across the globe. Understanding their gemological properties not only aids in identification but also informs the proper care required to preserve their beauty for generations. Whether chosen for their symbolic meanings, historical significance, or simply their captivating hues, these three gems ensure that anyone born in December has a wealth of magnificent options to call their own.