The final month of the year is unique in the world of gemstones, offering not one, but three official birthstones. While turquoise holds the longest-standing traditional claim as December's birthstone, modern lists have expanded to include zircon and tanzanite. This triad represents a fascinating spectrum of geological origins, historical lore, and visual characteristics, providing a diverse palette for those born in the winter month. The gemstone associated with December is not a single entity but a collection of stones, each with its own story of formation, discovery, and cultural significance. From ancient talismans of protection to modern symbols of clarity and rarity, December's birthstones cater to a wide range of tastes and preferences, making them a compelling subject for gemstone enthusiasts and jewelry buyers alike.
The assignment of specific gemstones to months has a complex history, with modern conventions largely solidified in the early 20th century. For December, the journey from a single traditional stone to a trio of options reflects both the evolving gem market and the desire to offer more choice. The primary stone, turquoise, is one of the oldest known gem materials, valued for millennia across numerous civilizations. Its inclusion as a December birthstone is well-documented in historical tradition. In more recent times, the list has been officially expanded. Zircon, a gemstone often confused with the synthetic cubic zirconia, brings a brilliance and color range that has been prized for centuries. Most recently, tanzanite was added to the official list in 2002 by the American Gem Trade Association (AGTA), recognizing its growing importance in the gemstone market and its unique, vibrant color. This article will delve into the history, geology, and properties of these three remarkable gemstones, providing a comprehensive guide to the birthstones of December.
History and Lore
The historical narrative of December's birthstones is dominated by turquoise, with zircon and tanzanite playing more recent, though equally significant, roles.
Turquoise: An Ancient Talisman Turquoise is arguably the most historically significant of December's birthstones. Its use dates back thousands of years, with archaeological evidence pointing to ancient Egypt, Persia, and the Americas. The stone's name itself, derived from the French "pierre turquoise" meaning "Turkish stone," reflects its trade routes through Turkey to Europe. Ancient cultures revered turquoise for its protective qualities. It was believed to be a powerful talisman, warding off evil and danger. For instance, ancient Persian warriors and horsemen often adorned themselves and their horses with turquoise to ensure safety in battle. The stone was also associated with good fortune and success, a belief that persists to this day. In many cultures, turquoise was thought to be a direct link between the earth and the sky, and its color was said to change to warn its wearer of impending danger or illness, a phenomenon attributed to the stone's porosity and its reaction to oils and acids from the skin. This historical weight and the consistent association with protection and good luck cemented its status as the traditional December birthstone.
Zircon: The Stone of Clarity and Purity Zircon has a long and storied history, though it is often overshadowed by its more famous counterpart, diamond. For centuries, zircon was prized for its exceptional brilliance and fire, which rival that of diamond. In medieval Europe, zircon was believed to induce sleep, ward off evil spirits, and bring prosperity and honor to its wearer. It was also thought to promote wisdom and honor. Its high refractive index made it a popular diamond simulant, and for a long time, many "diamonds" in historical royal collections were later identified as zircon. The confusion between the words "zircon" and "cubic zirconia" (a synthetic diamond simulant created in the 1970s) has unfortunately tarnished zircon's reputation in the modern market, but its historical value as a natural gemstone of great beauty is undeniable. Blue zircon, in particular, has been a popular color for centuries and is the most common color associated with the December birthstone.
Tanzanite: The Gemstone of a Generation Tanzanite is the newest addition to the December birthstone family, with its history beginning in the late 20th century. It was discovered in 1967 in the Merelani Hills of Tanzania, near Mount Kilimanjaro. Its discovery is a relatively recent event in the gemological world, making it a gemstone of a generation. The stone was initially brought to the attention of the international market by the jewelry company Tiffany & Co., which recognized its stunning blue-violet hue and marketed it heavily in the 1970s. Tiffany named the gem after its country of origin, Tanzania. Due to its singular source location and its rapid rise in popularity, tanzanite was declared a "gemstone of a generation" and is believed to be available for only a limited time. In 2002, the American Gem Trade Association officially added tanzanite to its list of modern birthstones for December, recognizing its unique color and growing significance in the jewelry industry. Its lore is modern, often associated with transformation and new beginnings, aligning with its recent discovery.
Geological Formation and Sources
The three December birthstones originate from vastly different geological environments and are sourced from distinct locations around the world.
Turquoise Formation and Sources Turquoise is not a single mineral but a hydrated phosphate of copper and aluminum. It forms in arid regions where acidic, copper-rich groundwater seeps through rocks containing aluminum and phosphorus minerals. Over geological time, this process creates nodules or veins of turquoise. The stone is typically found in association with host rocks like limonite, sandstone, and chert. Its color, ranging from sky blue to green, is directly influenced by the amount of copper (blue) and iron (green) present in its formation. Major sources of turquoise include the United States (particularly Arizona, Nevada, and New Mexico), Iran, China, and Egypt. The specific mine location significantly impacts the stone's color, matrix, and durability, with some varieties like "Lander Blue" or "Royston" being highly sought after by collectors.
Zircon Formation and Sources Zircon is a zirconium silicate mineral (ZrSiO₄) and is one of the hardest minerals on Earth, with a hardness of 7.5 on the Mohs scale. It forms primarily in igneous rocks, such as granite and syenite, and can also be found in metamorphic rocks. Zircon crystals are often found as detrital grains in sedimentary deposits, having been weathered from their original host rock and transported. It is a common mineral in many parts of the world. While zircon is mined in many countries, significant commercial sources include Australia (which produces most of the world's gem-quality zircon), Cambodia, Myanmar, and Sri Lanka. The stone's durability makes it suitable for various jewelry applications, though its brittleness requires careful handling during cutting and setting.
Tanzanite Formation and Sources Tanzanite is a variety of the mineral zoisite (a calcium aluminum silicate hydroxide). Its unique blue-violet color is the result of heat treatment of naturally occurring brownish zoisite crystals. The gem forms in the Merelani Hills of Tanzania, a single-source mining area. The geological conditions in this specific region, involving the interaction of heat, pressure, and mineral-rich fluids, created the unique conditions necessary for the formation of this blue variety. The mining area is small, roughly 4 square kilometers, which contributes to its rarity. The primary source is the TanzaniteOne mining operation, which controls the majority of the world's supply. The limited geographic origin makes tanzanite one of the most location-specific gemstones in the world.
Gemological Properties
Understanding the physical and optical properties of these gemstones is crucial for both identification and care. The following table summarizes key gemological characteristics for turquoise, zircon, and tanzanite.
| Gemstone | Chemical Composition | Hardness (Mohs) | Refractive Index | Specific Gravity | Crystal System | Typical Treatments |
|---|---|---|---|---|---|---|
| Turquoise | Hydrated copper aluminum phosphate | 5 - 6 | 1.61 - 1.65 | 2.6 - 2.9 | Triclinic (amorphous) | Waxing, stabilization, dyeing |
| Zircon | Zirconium silicate (ZrSiO₄) | 6.5 - 7.5 | 1.92 - 2.01 | 4.6 - 4.7 | Tetragonal | Heat treatment (to improve color) |
| Tanzanite | Calcium aluminum silicate hydroxide (Ca₂Al₃(SiO₄)₃(OH)) | 6.5 - 7 | 1.69 - 1.70 | 3.35 - 3.38 | Orthorhombic | Heat treatment (standard) |
Turquoise Properties Turquoise is a relatively soft and porous gemstone, with a hardness ranging from 5 to 6 on the Mohs scale. This makes it susceptible to scratching and damage from chemicals, cosmetics, and even perspiration. Its porosity is why many turquoise gems are treated. Common treatments include waxing or oiling to enhance luster and color, and stabilization (impregnation with a clear resin or plastic) to improve durability and reduce porosity. Some turquoise may also be dyed to achieve a more uniform blue color. The stone's color is its most prized characteristic, ranging from a delicate sky blue to a rich greenish-blue, often with a distinctive black or brown matrix (the host rock inclusions).
Zircon Properties Zircon is one of the most brilliant natural gemstones due to its high refractive index (1.92-2.01), which is higher than that of diamond. It also possesses high dispersion (0.039), giving it exceptional fire. However, zircon is brittle and has a perfect cleavage in two directions, making it susceptible to chipping or cracking if struck. Its hardness of 6.5 to 7.5 makes it durable enough for most jewelry, but it requires careful handling. Zircon occurs in a variety of colors, including blue, golden yellow, red, and green. The most common color for December birthstone jewelry is blue, which is typically achieved through heat treatment of brownish zircon. Untreated zircon is rare and highly valued.
Tanzanite Properties Tanzanite is a relatively durable gemstone with a hardness of 6.5 to 7 on the Mohs scale, making it suitable for jewelry, though not as hard as sapphire or diamond. It exhibits strong trichroism, meaning it can show three different colors—blue, violet, and burgundy—depending on the crystal orientation. This property is a key identifier for tanzanite. The gem is almost always heat-treated to remove the brownish tones and bring out its signature blue-violet color. This treatment is permanent and is considered standard for the gem. Tanzanite's color ranges from a light lavender to a deep, saturated blue-violet, with the most valuable stones displaying a rich, intense hue.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, all three December birthstones are imbued with rich symbolism and metaphysical beliefs, though these attributes vary significantly across cultures and time periods.
Turquoise: The Stone of Protection As mentioned in historical lore, turquoise is primarily a stone of protection, good fortune, and success. It is believed to absorb negative energy and protect the wearer from harm. In many cultures, it is also associated with healing, balance, and emotional stability. It is said to promote inner calm and peace, making it a popular stone for meditation. Its connection to the sky and water elements in various traditions reinforces its symbolism of tranquility and spiritual grounding.
Zircon: The Stone of Wisdom and Honor Zircon has long been associated with wisdom, honor, and purity. It is believed to enhance self-confidence and attract prosperity and success. Some traditions hold that zircon can help with spiritual grounding and provide clarity of thought. Its brilliant sparkle is thought to mirror the light of wisdom, guiding the wearer toward truth and understanding. The stone is also associated with restful sleep and the warding off of nightmares.
Tanzanite: The Stone of Transformation Given its recent discovery, tanzanite's metaphysical lore is more modern. It is often called the "stone of transformation" and is believed to facilitate spiritual awakening and higher consciousness. It is associated with the throat and third eye chakras, promoting clear communication and intuitive insight. Some believe tanzanite can help release old patterns and embrace new beginnings, making it a powerful stone for personal growth and change. Its unique color is said to bridge the physical and spiritual realms.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, with each requiring specific attention due to their distinct physical properties.
Caring for Turquoise Due to its relative softness and porosity, turquoise requires gentle care. It should be cleaned only with a soft, dry cloth. Avoid using ultrasonic cleaners, steam cleaners, or harsh chemicals, as these can damage the stone or strip away any treatments. It is also advisable to remove turquoise jewelry before engaging in activities that could cause impact or exposure to lotions, perfumes, and perspiration. To preserve its color and luster, store turquoise separately from harder gemstones to prevent scratching.
Caring for Zircon Zircon's brittleness and perfect cleavage make it susceptible to chipping. It should be handled with care and protected from hard impacts. Cleaning can be done with warm, soapy water and a soft brush, but avoid ultrasonic and steam cleaners, which can cause thermal shock and lead to cracking. It is best to remove zircon jewelry during strenuous activities. Due to its high refractive index, zircon can collect dust and oil, which may dull its brilliance, so regular gentle cleaning is recommended.
Caring for Tanzanite Tanzanite, with a hardness of 6.5 to 7, is reasonably durable but still requires care. It is best cleaned with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaners, as the heat and vibrations can potentially damage the stone. Like zircon, tanzanite should be stored carefully to avoid scratches from other, harder gemstones. It is also advisable to remove tanzanite jewelry before physical activities to prevent impacts that could cause chipping.
Conclusion
December's birthstones—turquoise, zircon, and tanzanite—offer a remarkable journey through gemological history, from ancient talismans to modern marvels. Turquoise stands as a testament to enduring tradition, its protective lore and distinctive color securing its place for millennia. Zircon provides a bridge between the ancient and the modern, a gemstone of brilliant fire and clarity that has been cherished for centuries, often mistaken for diamonds in royal treasuries. Tanzanite represents the pinnacle of modern gem discovery, a stone of singular origin whose vibrant hue and transformative symbolism have captured the contemporary imagination. Together, they form a diverse and compelling trio that provides options for every preference, whether one is drawn to the soft, earthy tones of turquoise, the dazzling brilliance of zircon, or the vivid, otherworldly color of tanzanite. For those born in December, these gemstones are more than mere adornments; they are a connection to a rich tapestry of geological processes, human history, and cultural belief, making them a truly special and meaningful choice.