The twelfth month of the Gregorian calendar, December, is a period of stark beauty, marked by the solstice, long nights, and the culmination of the year. For those born in this month, their birthstones—turquoise, zircon, and tanzanite—offer a vibrant counterpoint to the winter landscape. These three distinct gemstones, each with unique geological origins, historical narratives, and symbolic meanings, form a fascinating triad that represents the depth and diversity of December. While turquoise has ancient roots as a talisman of protection, zircon boasts a history intertwined with mistaken identity and dazzling fire, and tanzanite is a modern marvel, a geological rarity discovered in the 20th century. This article delves into the lore, properties, and significance of these three December birthstones, providing a detailed exploration for gemstone enthusiasts, jewelry buyers, and students of gemology.
Historical Lore and the Path to Modern Birthstones
The association of specific gemstones with months of the year has evolved over centuries, with roots in both ancient traditions and modern marketing. The modern list of birthstones, largely standardized in the 20th century, draws upon historical beliefs and commercial considerations. For December, the journey to its current trio of gemstones is a story of both ancient symbolism and contemporary discovery.
Turquoise: An Ancient Talisman Turquoise is arguably the most ancient of the December stones, with a history spanning millennia. It is considered a symbol of good fortune and success, a belief that has persisted from ancient times to the present day. Its name is derived from the French pierre turquoise, meaning "Turkish stone," reflecting its historical trade routes through Turkey to Europe. For centuries, cultures from ancient Egypt to the Persian Empire and the Native American tribes of the Southwest have prized turquoise for its captivating sky-blue to greenish-blue hue, believing it to be a protective stone and a conduit to spiritual wisdom. Its inclusion in the December birthstone list is deeply rooted in this long-standing cultural significance.
Zircon: A Gem of Mistaken Identity and Brilliance Zircon is one of the oldest minerals on Earth, with crystals found in rocks that are billions of years old. However, its journey into the birthstone canon is complicated by its historical confusion with another gemstone. For centuries, the term "zircon" was often used interchangeably with "jacinth," a name for the orange-brown variety of hyacinth, and was frequently confused with synthetic cubic zirconia, a diamond simulant invented in the 1970s. This confusion has sometimes clouded its reputation. Despite this, zircon has been valued for its exceptional brilliance and fire, which can rival that of a diamond. It is available in a variety of colors, but the blue zircon, often created by heat-treating brownish zircon, has become particularly associated with December. Its historical use in jewelry dates back to at least the Middle Ages, and it was believed to promote honor and purity.
Tanzanite: A 20th-Century Geological Marvel In stark contrast to the ancient histories of turquoise and zircon, tanzanite is a newcomer to the gemstone world. It was discovered in 1967 in Tanzania, East Africa, making it one of the most significant gemological finds of the 20th century. Its discovery is attributed to a local Maasai tribesman who found vibrant blue-violet crystals in the Merelani Hills of northern Tanzania. The gemstone was quickly recognized for its extraordinary color and rarity. Tiffany & Co. introduced it to the global market in 1968, naming it after the country of its origin. Marketing campaigns highlighted its rarity, claiming it to be rarer than diamonds, which, while a compelling narrative, underscores its genuine scarcity. Its inclusion as a December birthstone is a modern addition, reflecting its rapid ascent to prominence in the jewelry industry. While sources do not explicitly state the official adoption date for tanzanite as a December birthstone, its presence in all provided sources listing December's stones confirms its status in contemporary tradition.
Geological Formation and Global Sources
The origins of these gemstones are as diverse as their appearances, formed under different geological conditions and sourced from distinct regions of the world.
Turquoise: A Hydrous Copper Mineral Turquoise is not a silicate mineral but a hydrous copper and aluminum phosphate. It forms in arid regions where acidic, copper-rich groundwater percolates through aluminum-bearing rocks, such as volcanic ash or sedimentary rock. Over time, the solution deposits the turquoise mineral in cracks and voids. This process results in the gemstone's characteristic porous, often veined, and sometimes matrix-included appearance. Major sources of turquoise include the United States (particularly Arizona, New Mexico, and Nevada), Iran, China, and Egypt. The specific location and mining conditions can significantly influence the stone's color, hardness, and matrix pattern, which are critical factors in its valuation.
Zircon: A Silicate Crystal from High-Temperature Environments Zircon is a zirconium silicate (ZrSiO₄) that crystallizes from magma in igneous rocks like granite and syenite. It can also form during metamorphism. As one of the oldest minerals, it is often found as detrital grains in sedimentary deposits, having survived erosion and transport from their original igneous source. The gem-quality crystals used in jewelry are mined from alluvial (river) deposits or hard rock mines. The most significant sources for gem zircon are Cambodia, Sri Lanka, and Thailand, though it is also found in Myanmar, Australia, and the United States. The blue color in zircon is typically achieved by heating brownish zircon at high temperatures, a stable process that does not fade over time.
Tanzanite: A Unique Geological Phenomenon Tanzanite's formation is a geological rarity. It is a variety of the mineral zoisite, specifically the blue-violet to purple form known as blue zoisite. Its unique color is caused by trace amounts of vanadium within its crystal structure. The conditions required for its formation are exceptionally specific: a unique geological event where heat from a massive intrusion of magma altered pre-existing zoisite crystals, followed by a subsequent period of tectonic activity that exposed these crystals to surface weathering. This precise set of circumstances is believed to have occurred only in a single, small area of the Merelani Hills in northern Tanzania. This extreme geographic limitation is the primary reason for tanzanite's rarity. Unlike turquoise and zircon, which can be found in multiple locations worldwide, tanzanite is mined almost exclusively from this one deposit.
Gemological Properties: A Scientific Comparison
Understanding the physical and optical properties of these gemstones is essential for both identification and practical care. The following table summarizes key gemological data for turquoise, zircon, and tanzanite, based on established gemological standards.
| Property | Turquoise | Zircon (Blue) | Tanzanite |
|---|---|---|---|
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | ZrSiO₄ | Ca₂Al₃(SiO₄)₃(OH) |
| Crystal System | Triclinic | Tetragonal | Orthorhombic |
| Hardness (Mohs) | 5 - 6 | 6.5 - 7.5 | 6.5 - 7 |
| Specific Gravity | 2.60 - 2.90 | 4.60 - 4.70 | 3.10 - 3.38 |
| Refractive Index | 1.610 - 1.650 | 1.92 - 1.98 | 1.691 - 1.700 |
| Luster | Waxy to subvitreous | Adamantine to vitreous | Vitreous |
| Transparency | Opaque to translucent | Transparent to translucent | Transparent to translucent |
| Notable Characteristics | Often porous, frequently contains matrix (host rock). Color can fade with prolonged UV exposure. | High refractive index and strong dispersion (fire). Blue color is typically heat-treated. | Strong trichroism (shows three colors: blue, violet, and burgundy). Color can fade with heat and light. |
Turquoise: With a hardness of 5 to 6 on the Mohs scale, turquoise is relatively soft compared to many gemstones, making it susceptible to scratching and abrasion. Its porous nature means it can absorb chemicals, lotions, and oils, which can alter its color and luster. The presence of "matrix" (the host rock in which it formed) is common and can be a desirable feature, adding to its unique character.
Zircon: Zircon is significantly harder and more durable than turquoise, with a Mohs hardness of 6.5 to 7.5. Its most remarkable properties are its high refractive index and strong dispersion, which give it exceptional brilliance and fire, often compared to that of a diamond. However, zircon can be brittle due to its tetragonal crystal structure and is prone to chipping or cracking if struck. The blue color in commercial zircon is almost always the result of controlled heat treatment of brownish material, a permanent and accepted practice in the gem trade.
Tanzanite: With a hardness of 6.5 to 7, tanzanite is suitable for jewelry but requires more care than harder stones like sapphire. Its most distinctive gemological feature is strong trichroism—the ability to display three different colors from different crystallographic directions. In its natural state, tanzanite typically shows hues of blue, violet, and burgundy. Most tanzanite sold today has been heat-treated to a uniform blue or violet-blue color, a process that mimics the natural geological heating that gave the stone its original color. This treatment is stable and does not degrade over time.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these gemstones have been imbued with symbolic meaning and metaphysical properties across various cultures and eras.
Turquoise: Universally regarded as a stone of protection, turquoise is believed to ward off negative energy and bring good fortune. In many cultures, it is considered a sacred stone. For Native American tribes, it represents the sky and water and is used in ceremonies and jewelry. In Persian tradition, it was worn as an amulet to guard against the "evil eye" and to ensure a safe journey. Its association with success and good luck makes it a popular gift for travelers and those embarking on new ventures.
Zircon: Historically, zircon was believed to promote honor, purity, and prosperity. In some traditions, it was thought to aid in sleep and bring wisdom. Its fiery brilliance has linked it to concepts of light and energy. While not as heavily documented in ancient lore as turquoise, zircon has been valued as a stone of clarity and spiritual grounding.
Tanzanite: As a modern gemstone, tanzanite's metaphysical attributes are more contemporary. It is often associated with transformation, intuition, and higher consciousness. Its unique trichroic nature is said to symbolize the integration of mind, body, and spirit. It is marketed as a stone of spiritual awakening and is believed to facilitate communication and a deeper understanding of one's life purpose. Its rarity is also tied to its symbolism of uniqueness and individuality.
Care and Cleaning: Preserving Your December Gems
Proper care is essential to maintain the beauty and longevity of these gemstones, with each requiring specific handling due to their distinct properties.
Turquoise Care: Due to its porosity and relatively low hardness, turquoise requires gentle care. - Avoid Chemicals: Keep turquoise away from chemicals, including perfumes, lotions, hairsprays, and household cleaners, which can penetrate the stone and cause discoloration or damage. - Cleaning: Clean turquoise jewelry with a soft, dry cloth. For a deeper clean, use lukewarm water and a mild soap, but do not soak it. Dry it immediately and thoroughly with a soft cloth. Ultrasonic and steam cleaners are not recommended. - Storage: Store turquoise separately from other jewelry to prevent scratches. Keep it away from direct sunlight and extreme heat, as prolonged exposure can cause the color to fade.
Zircon Care: Zircon's hardness is a advantage, but its brittleness requires caution. - Handling: Due to its tendency to chip, avoid wearing zircon in settings where it might receive hard impacts (e.g., rings for daily wear). It is better suited for earrings, pendants, and brooches. - Cleaning: Zircon can be cleaned with warm soapy water and a soft brush. It is safe for ultrasonic cleaners, but caution is advised if the stone has inclusions or fractures. Steam cleaning is generally not recommended due to the risk of thermal shock. - Storage: Store zircon in a fabric-lined box or a soft pouch to protect it from scratches and blows.
Tanzanite Care: Tanzanite's cleavage and sensitivity to heat and light demand careful attention. - Avoid Heat and Light: Prolonged exposure to strong light and heat can cause the color of tanzanite to fade. It should be stored away from direct sunlight and not worn in high-heat environments. - Cleaning: Clean tanzanite with warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as the vibrations can cause internal fractures. Steam cleaning is also not recommended. - Setting: Due to its good cleavage in one direction, tanzanite should be set in protective settings, such as bezels, especially for rings, to prevent chipping.
Conclusion
The birthstones of December—turquoise, zircon, and tanzanite—offer a compelling narrative of geological diversity, historical depth, and cultural significance. From the ancient protective talisman of turquoise to the brilliant, fire-filled zircon and the rare, trichroic marvel of tanzanite, each stone provides a unique window into the Earth's creative processes and human history. For those born in the final month of the year, these gems are more than just beautiful adornments; they are symbols of good fortune, transformation, and rarity, perfectly mirroring the reflective and celebratory nature of December itself. Understanding their origins, properties, and care ensures that these remarkable stones can be cherished for generations to come.