The month of December is uniquely distinguished in the world of gemology by its association with not one, but three official birthstones: turquoise, tanzanite, and blue zircon. Each of these gems possesses a distinct geological origin, historical narrative, and set of gemological properties, offering a diverse palette of blue hues that have captivated humanity for millennia. While turquoise stands as one of the oldest known gemstones, tanzanite represents a remarkable 20th-century discovery, and blue zircon offers a brilliant, diamond-like sparkle. Together, they provide December-born individuals with a rich array of choices, each stone carrying its own story of protection, transformation, and clarity. This article will delve into the history, geological formation, gemological properties, and symbolic meanings of these three celebrated December birthstones, drawing exclusively from the provided source materials to present a comprehensive overview for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore
The historical journey of December's birthstones is as varied as the gems themselves, spanning ancient civilizations to modern gemological standards.
Turquoise is unequivocally the oldest of the December stones, with a documented history stretching back to 4000 BC. Its enduring appeal is evident in its deep cultural significance across the globe. The stone has been cherished for millennia, not merely as an ornament but as a talisman believed to offer protection and peace. Its status as a traditional birthstone is ancient, and it remains a cornerstone of December's gemological identity.
Tanzanite, in stark contrast, is a modern addition to the birthstone canon. This gem is a relatively recent discovery, having been found only in 1967 in Tanzania, which gives the stone its name. Its recognition as a December birthstone is also recent; it was added as America's December birthstone in 2002, by which time it was already recognized in Britain. As a 20th-century find, tanzanite's lore is intertwined with concepts of spiritual growth, transformation, and new beginnings, aligning with its contemporary and rare nature.
Blue Zircon occupies a middle ground, possessing both ancient roots and modern standardization. Zircon is one of Earth's oldest minerals, and the blue variety has been traditionally associated with December for a long period. Its formal status in modern U.S. gemology was solidified in 1952 when it replaced lapis lazuli as the official December birthstone. This change was later affirmed by the American Gem Trade Association in February 2013, which confirmed blue zircon's position. The stone is deeply linked to tranquility, calmness, and clear communication.
It is important to note that the provided sources also mention a wider array of gemstones historically associated with December across different cultures and calendars. For instance, ruby is cited as the ancient birthstone for December in old Arabic, Hebrew, Italian, Roman, and Indian (Ayurvedic) calendars. Onyx (a black banded chalcedony) is listed as the December birthstone in the old Tibetan calendar. Bloodstone (heliotrope), a green chalcedony with red inclusions, is a traditional December birthstone dating back to the 15th century. Lapis lazuli was a modern U.S. birthstone until 2013, and topaz (specifically blue topaz) is recognized in the Hindu calendar. Chrysoprase, an apple to deep green chalcedony, is a December stone in the old Russian calendar. However, for the purpose of this article focusing on the three official modern birthstones, we will concentrate on turquoise, tanzanite, and blue zircon.
Geological Formation and Sources
Understanding the geological origins of these gems provides insight into their rarity and unique characteristics.
Turquoise is a phosphate mineral, an opaque gemstone that forms in arid regions where acidic, copper-rich water percolates through rocks containing aluminum and phosphorus. Its distinctive sky-blue to blue-green color is derived from copper, while the greenish hues come from iron. The stone is often characterized by its natural veining, which is a matrix of host rock (such as quartz or pyrite) that becomes embedded within the turquoise during formation. While the sources do not specify modern mining locations, its ancient and widespread use suggests a historical presence in regions like the Middle East, Egypt, and the American Southwest.
Tanzanite is a variety of the mineral zoisite. Its formation is exceptionally rare, as it is found in only one known location on Earth: the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. This geographic exclusivity is a key factor in its value and allure. The gem is noted for its pleochroic property, meaning it can display different colors—blue, violet, and burgundy—when viewed from different crystal directions. This phenomenon is a direct result of its specific geological formation and is a hallmark of the stone.
Blue Zircon is a mineral belonging to the zircon group, with a chemical composition of zirconium silicate (ZrSiO₄). It is found in a variety of colors, but the blue variety used for jewelry is typically heat-treated from brown zircon crystals. These crystals are sourced from various locations globally, including Cambodia, Myanmar, and Sri Lanka, though the provided sources do not specify current primary mining regions. The stone's exceptional brilliance and fire are attributed to its high refractive index, which is among the highest of all gemstones, rivaling that of diamond.
Gemological Properties
The physical and optical properties of these three gems define their durability, appearance, and suitability for jewelry.
| Gemstone | Chemical Composition | Hardness (Mohs Scale) | Crystal System | Key Optical Property | Typical Color Range |
|---|---|---|---|---|---|
| Turquoise | Hydrated copper/aluminum phosphate | 5 - 6 | Triclinic | Opaque | Sky-blue to blue-green, often with veining |
| Tanzanite | Calcium aluminum silicate hydroxide | 6.5 - 7 | Orthorhombic | Pleochroic | Violet-blue to rich indigo |
| Blue Zircon | Zirconium silicate (ZrSiO₄) | 6.5 - 7.5 | Tetragonal | High refractive index (brilliant sparkle) | Brilliant blue, bright and sparkling |
Turquoise is a relatively soft and porous stone, with a hardness of 5 to 6 on the Mohs scale. This makes it susceptible to scratching and chemical damage. Its opacity means it does not have the clarity or brilliance of transparent gems. The distinctive veining is a natural characteristic, not a flaw, and is often prized for its unique patterns.
Tanzanite is slightly harder than turquoise, with a hardness of 6.5 to 7. However, it is still considered somewhat fragile for everyday wear in rings. Its most celebrated property is its strong pleochroism, which can show violet, blue, and reddish hues depending on the cut and orientation. This dynamic color shift is a major part of its appeal. It is a transparent gemstone, allowing for faceted cuts that enhance its color play.
Blue Zircon is the hardest and most durable of the three, with a hardness of 6.5 to 7.5, making it suitable for a variety of jewelry types. Its most defining gemological feature is its exceptional brilliance and fire, which results from its high refractive index (1.92-2.01). This gives it a diamond-like sparkle that is unmatched by the other December stones. It is a transparent gem, and its bright, clear blue color is highly sought after.
Symbolism and Metaphysical Beliefs
Across cultures and eras, these stones have been imbued with symbolic meanings and metaphysical properties.
Turquoise is universally regarded as a stone of protection, peace, balance, and healing. It is believed to bring calmness and good fortune to the wearer, acting as a shield against negativity. Its soothing blue-green color is associated with tranquility and emotional stability.
Tanzanite is linked to spiritual growth, transformation, and intuition. Its recent discovery and unique color are often associated with new beginnings and expanding one's perspective. It is considered a stone for those undergoing significant personal change, helping to free the mind from negativity and heighten awareness.
Blue Zircon is associated with tranquility, calmness, clear communication, and spiritual growth. It is believed to relieve mental tension, increase luck, and promote a sense of balance and prosperity. Some sources specifically link it to the Throat Chakra, which is associated with expression and communication.
The other historically associated stones also carry specific meanings: Ruby is believed to strengthen the mind and bestow courage. Onyx is a grounding stone that protects from negativity. Bloodstone enhances courage and physical strength. Lapis Lazuli is thought to heighten awareness and expand perspective. Topaz (blue) is believed to increase physical and spiritual strength. Chrysoprase is believed to enhance emotional balance and prevent depression.
Care and Cleaning
The proper care for these gems is dictated by their physical properties, primarily their hardness and porosity.
Turquoise, due to its lower hardness (5-6) and porosity, requires the most careful handling. It should be protected from scratches, chemicals (including perfumes, lotions, and household cleaners), and prolonged exposure to water or heat. Cleaning should be done with a soft, dry cloth. Avoid ultrasonic cleaners and steam cleaning.
Tanzanite (hardness 6.5-7) is also somewhat fragile. It is best suited for earrings, pendants, and brooches rather than daily-wear rings. It should be protected from hard blows and extreme temperature changes. Cleaning can be done with warm water, a mild soap, and a soft brush. Ultrasonic cleaners are not recommended.
Blue Zircon (hardness 6.5-7.5) is the most durable of the three, but it still requires careful handling. It can be susceptible to abrasion and should be stored separately from other jewelry to prevent scratching. While it is generally safe for standard cleaning methods, it is wise to avoid harsh chemicals and sudden temperature shocks. A soft brush with mild soap and warm water is the safest cleaning method.
Conclusion
The December birthstones—turquoise, tanzanite, and blue zircon—offer a remarkable trifecta of beauty, history, and significance. From the ancient, protective warmth of turquoise to the transformative, pleochroic allure of tanzanite and the brilliant, communicative clarity of blue zircon, each stone provides a distinct narrative. Their selection allows for a personal expression of style and meaning, whether one is drawn to millennia of history, rare geographic exclusivity, or exceptional gemological brilliance. Understanding their unique properties, origins, and care requirements empowers enthusiasts and collectors to make informed choices, ensuring these captivating gems can be cherished for generations to come.