The final month of the year is uniquely distinguished in the world of birthstones by not having one, but three official gemstones: Turquoise, Tanzanite, and Zircon. This trio offers a remarkable spectrum of color, from the serene sky-blue of ancient Turquoise to the vivid violet-blue of modern Tanzanite and the brilliant fire of Zircon. For those born in December, this provides a rich palette of choices, each stone carrying its own deep history, geological story, and symbolic significance. This article delves into the origins, properties, and cultural lore of these three captivating gems, drawing upon established historical and gemological knowledge to present a comprehensive guide for enthusiasts, collectors, and anyone captivated by the science and beauty of these December birthstones.
The Historical and Cultural Journey of December's Gems
The tradition of assigning specific gemstones to each month of the year has evolved over centuries, with December's stones reflecting a blend of ancient symbolism and modern discovery. The concept of birthstones itself has roots in historical texts like the Breastplate of Aaron described in the Book of Exodus, which featured twelve different stones representing the tribes of Israel. While the modern list of birthstones was standardized by the American National Association of Jewelers in 1912, the stones associated with December have particularly diverse origins.
Turquoise, the traditional and most ancient of the three, has been revered for thousands of years. Its name derives from the French "pierre turquoise," meaning "Turkish stone," as it was brought to Europe from Persia via Turkish traders. However, its use predates these trade routes by millennia. Ancient Egyptians mined turquoise in the Sinai Peninsula, using it for intricate jewelry, amulets, and burial masks, believing it offered protection in the afterlife. The stone was also highly valued by Native American cultures in the Southwestern United States, where it became a central element in their spiritual and artistic expressions. Its association with December is likely linked to its sky-blue color, reminiscent of winter's clear, cold skies. As noted in historical traditions, Turquoise has long been considered a symbol of good fortune and success, a belief that has persisted across continents and eras.
In stark contrast, Tanzanite is a gemstone of the modern age. Its history began in 1967 in the Merelani Hills of Tanzania, near the base of Mount Kilimanjaro. This single-source gemstone was discovered by a local Masai tribesman and subsequently brought to the attention of the international gem trade by the Tiffany & Co. jewelry house, which recognized its stunning violet-blue hue and began marketing it in 1968. Tanzanite's discovery was so recent that it lacks the ancient lore of Turquoise or Zircon, but it was quickly embraced for its exceptional color and relative rarity. Its inclusion as a birthstone for December is a 20th-century addition, reflecting the evolution of birthstone lists to include newly significant and commercially available gems. Some sources emphasize its rarity, noting that it is found in only one location on Earth, making it rarer than diamonds.
Zircon possesses one of the oldest histories of any gemstone. It is not to be confused with the synthetic cubic zirconia (CZ), a common diamond simulant. Natural zircon is a naturally occurring mineral and one of the oldest materials on Earth, with some specimens dating back over 4 billion years. For centuries, it was often mistaken for more expensive gems like diamond or topaz. In the Middle Ages, it was believed to promote honor, purity, and wisdom, and was used to ward off evil spirits and encourage prosperity. The most prized color for zircon is a brilliant blue, often achieved through heat treatment of brownish crystals. This blue variety is particularly associated with December, though zircon occurs in a range of colors including yellow, green, red, and brown. Its historical journey from a misunderstood mineral to a celebrated birthstone underscores the dynamic nature of gemology.
Geological Formation and Global Sources
The formation of these three gemstones occurs under vastly different geological conditions, contributing to their unique properties and scarcity.
Turquoise is a hydrous phosphate mineral (chemical formula: CuAl₆(PO₄)₄(OH)₈·4H₂O) that forms in arid or semi-arid regions. It is a secondary mineral, meaning it forms through the alteration of pre-existing copper-rich minerals by water containing phosphorus. This process occurs in the upper levels of copper deposits, where acidic groundwater percolates through the rock, dissolving copper and aluminum and re-depositing them in veins and nodules. Major sources include the United States (particularly Arizona and New Mexico), Iran, Egypt, and China. The quality of Turquoise is heavily influenced by its source, with "sleeping beauty" turquoise from Arizona known for its pure, solid sky-blue color without matrix (the host rock), while other deposits may feature a distinctive spiderweb matrix.
Tanzanite is a variety of the mineral zoisite (chemical formula: Ca₂Al₃(SiO₄)₃(OH)). Its formation is linked to a unique geological event: the tectonic rifting of East Africa. Heat and pressure from this activity altered the zoisite crystals, causing the introduction of vanadium (and sometimes chromium) which imparts the signature blue-to-violet color. The process is believed to have occurred approximately 585 million years ago. Tanzanite is mined exclusively in a small area of the Merelani Hills in Tanzania, covering only about four square kilometers. This extreme geographic limitation is the primary reason for its rarity. The mining operation is challenging, and the gem is often found in rough form with distinct color zoning.
Zircon (chemical formula: ZrSiO₄) is a zirconium silicate that forms in igneous and metamorphic rocks. It is a primary mineral that crystallizes directly from magma as it cools. Its high durability and resistance to chemical weathering make it a common component in many rocks and a valuable tool for geochronology (dating rocks). While zircon is found in many locations worldwide, including Australia, Sri Lanka, Thailand, and Cambodia, the blue variety most prized for jewelry typically originates from these regions. The transformation from brownish to blue zircon is achieved through controlled heat treatment, a practice that has been used for centuries to enhance its color.
Gemological Properties: A Comparative Analysis
Understanding the physical and optical properties of these stones is crucial for identification, appreciation, and care. The following table summarizes key gemological data based on established standards.
| Property | Turquoise | Tanzanite | Zircon |
|---|---|---|---|
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | Ca₂Al₃(SiO₄)₃(OH) | ZrSiO₄ |
| Crystal System | Triclinic | Orthorhombic | Tetragonal |
| Color Range | Sky blue to blue-green, often with matrix (webbing) | Blue to violet, often pleochroic (shows different colors) | Colorless, blue, yellow, green, brown; blue is most popular for December |
| Mohs Hardness | 5 - 6 | 6.5 - 7 | 6.5 - 7.5 |
| Refractive Index | 1.610 - 1.650 | 1.691 - 1.700 | 1.925 - 2.015 |
| Specific Gravity | 2.60 - 2.90 | 3.35 | 4.6 - 4.7 |
| Durability & Care | Porous, susceptible to chemicals, heat, and impact. Avoid ultrasonic cleaners, steam, and harsh chemicals. | Good durability but can be brittle; best to avoid sudden temperature changes and ultrasonic cleaners. | Good durability but can be brittle; avoid sharp blows. Heat treatment is permanent but avoid extreme thermal shock. |
Turquoise is the softest of the three and is notably porous. This porosity allows it to absorb oils and chemicals, which can alter its color over time. Its hardness varies depending on the amount of water and impurities in the mineral structure. The presence of matrix (the host rock) can affect its overall durability. Its unique color comes from copper, while the blue-green hue is influenced by iron and zinc impurities.
Tanzanite is known for its strong trichroism, meaning it can display three different colors—typically blue, violet, and greenish-yellow—depending on the crystal's orientation. This property is a key identifier and adds to its visual appeal. It is relatively durable for jewelry but is softer than many other popular gems like sapphire or diamond. It is important to note that virtually all tanzanite on the market has been heat-treated to remove the brownish-yellow overtones and enhance the desirable blue-violet color. This treatment is stable and permanent.
Zircon is the most brilliant of the three, with a refractive index higher than that of diamond, giving it exceptional fire and sparkle. It is also strongly doubly refractive, which can sometimes be seen with a loupe. The blue color in zircon is almost always the result of heat treatment, which transforms brownish crystals into the coveted blue variety. While zircon is relatively hard and durable, it can be brittle due to its crystal structure and may cleave if struck with force.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each of December's birthstones carries a legacy of symbolic meaning and metaphysical belief.
Turquoise is perhaps the most symbolically rich of the three. Across cultures, it has been regarded as a stone of protection, healing, and good fortune. In many Native American traditions, it is considered a sacred stone that connects the wearer to the earth and sky, offering a spiritual bridge. Its color, reminiscent of water and sky, is linked to tranquility and peace. Historically, it was believed to change color to warn its owner of impending danger or illness. As a symbol of good fortune and success, it remains a popular talisman for travelers and those seeking stability.
Tanzanite, being a modern discovery, lacks millennia of lore but has quickly developed its own symbolism. It is often associated with transformation, intuition, and spiritual awakening. Its striking violet-blue color is linked to the higher chakras in some metaphysical systems, believed to facilitate communication and a deeper connection to one's inner self. Its rarity is seen as a symbol of uniqueness and individuality, making it a powerful stone for personal growth and metamorphosis.
Zircon has a long-standing reputation as a stone of wisdom, honor, and purity. In medieval times, it was believed to promote restful sleep and ward off evil spirits. The blue variety is particularly associated with clarity of thought and calmness. Its brilliant sparkle is thought to stimulate joy and vitality. Historically, it was also used as a protective amulet, believed to bring prosperity and success to its wearer. The stone's enduring nature, as one of the oldest minerals on Earth, connects it to concepts of eternity and legacy.
Care and Maintenance for Longevity
Proper care is essential to preserve the beauty and integrity of these gemstones, with each requiring specific attention due to their unique properties.
Turquoise Care: Due to its porosity and relatively low hardness, Turquoise requires the most delicate handling. It should be protected from chemicals, including perfumes, lotions, hairsprays, and household cleaners, which can cause discoloration or pitting. Avoid prolonged exposure to direct sunlight or heat, as this can cause fading and cracking. Clean Turquoise jewelry only with a soft, dry cloth. Never use ultrasonic cleaners, steam cleaners, or harsh soapy water. Store it separately to prevent scratching by harder materials.
Tanzanite Care: While more durable than Turquoise, Tanzanite should still be handled with care. It is best suited for jewelry that is not subjected to rough wear, such as earrings or pendants. Rings should be worn with caution. Avoid exposing Tanzanite to sudden temperature changes and ultrasonic cleaners, which can cause fractures. Clean it with warm water, a mild soap, and a soft brush, then rinse thoroughly and dry with a soft cloth. Store it in a fabric-lined box to prevent scratching.
Zircon Care: Zircon is generally durable but can be brittle. It is important to protect it from sharp blows and hard impacts. While it can withstand normal cleaning methods, it is advisable to avoid ultrasonic cleaners and extreme thermal shock. The best way to clean zircon is with warm, soapy water and a soft brush. It should be stored separately from other jewelry to avoid scratches, as it can be scratched by harder materials like diamond or sapphire.
Conclusion
The birthstones of December—Turquoise, Tanzanite, and Zircon—offer a fascinating study in contrast. From the ancient, earthy protection of Turquoise to the modern, transformative allure of Tanzanite and the brilliant, timeless wisdom of Zircon, each gemstone provides a unique narrative. Their diverse origins, from the arid mines of the American Southwest to the volcanic rifts of East Africa and the ancient igneous rocks of the globe, highlight the incredible geological processes that create natural beauty. Their symbolic meanings, spanning centuries of human culture, add a layer of depth to their physical attributes. For those born in December, this trio of gems provides not just a birthstone, but a choice of identity, whether one is drawn to the serene stability of Turquoise, the vivid transformation of Tanzanite, or the sparkling clarity of Zircon. Understanding their properties and history allows for a deeper appreciation of these remarkable gifts from the Earth.