December stands unique in the calendar of birthstones, offering not one, but four distinct gemstones to represent its month. This multiplicity is a modern convenience, providing a spectrum of blue hues from sky-like clarity to deep violet-blue, each with its own geological story, historical legacy, and symbolic meaning. The four recognized December birthstones—turquoise, tanzanite, zircon, and blue topaz—reflect the winter season's cool palette and offer jewelers and wearers a remarkable range of choices in terms of color, durability, and price. While turquoise and zircon have ancient roots, tanzanite and blue topaz represent more recent additions to the birthstone list, each gaining prominence through unique geological discoveries and commercial appeal. This article delves into the history, formation, gemological properties, and cultural significance of each of these four blue jewels, providing a definitive guide for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore
The journey of December's birthstones through history is a tapestry of ancient civilizations, trade routes, and modern marketing. Turquoise, the most ancient of the four, has been cherished for millennia. Evidence of its use dates back over 3,000 years, with Chinese artisans carving it during that period. The pharaohs and rulers of ancient Egypt adorned themselves with this semi-translucent to opaque blue-green gem, a testament to its high value and perceived power. Its lore is deeply protective; from the 13th century onward, it was believed to safeguard the wearer from falls, particularly from horses, and would break into pieces at the approach of danger. Hindu mystics associated it with wealth, believing that seeing a turquoise after the new moon ensured fantastic fortune. For Native Americans, particularly the Apache, turquoise was a spiritual guide; they believed one could find it by following a rainbow to its end, linking the gem to celestial phenomena and good luck.
Zircon is one of the oldest known gemstones, with a history that spans centuries. Its name is often confused with the synthetic cubic zirconia, but natural zircon is a distinct and ancient mineral. The 1952 update by the Jewelry Industry Council of America added zircon to December’s list, solidifying its place as a traditional birthstone. Historically, it has been associated with clarity, wisdom, and a sense of balance. Its brilliant blue variety, which is often heat-treated to achieve its vibrant color, has been prized for its fire and brilliance, rivaling more expensive diamonds in its scintillation.
The modern additions to the December lineup reflect evolving tastes and geological discoveries. Blue topaz, while found throughout history, has an exact origin that remains unknown. Its rise to prominence is a story of modern gemology and commercial strategy. In 1912, the National Association of Jewelers standardized the unofficial American birthstones, a list that was updated in 1952 to include zircon for December. Blue topaz itself gained mainstream popularity later, its deep, inky blues and light aqua shades becoming a favorite for contemporary jewelry. Some sources suggest that the expansion of December’s birthstones was to offer more affordable options, and blue topaz, with its relatively accessible price point, fit this role perfectly. It is now considered the official state gem of Texas, a modern designation that underscores its American appeal.
Tanzanite is the newest and most geographically restricted of the four. Its story begins not in antiquity, but in 1967 in the Merelani Hills of Tanzania, East Africa. This single-source gemstone was added to the official birthstone list in 2002, making it a very modern addition. Its rapid ascent to fame is due to its unique color and the powerful marketing efforts of Tiffany & Co., which recognized its potential and introduced it to the global market in the late 1960s. Symbolically, tanzanite represents transformation and new beginnings, a fitting metaphor for its sudden appearance on the gemological scene and its dramatic violet-blue hue.
Geological Formation and Sources
The origins of these four gemstones are as diverse as their colors. Turquoise is an opaque mineral, a hydrated phosphate of copper and aluminum that forms in arid regions where acidic, copper-rich groundwater percolates through aluminum-bearing rocks. This process creates nodules and veins, often incorporating remnants of the host rock, known as matrix, which can create distinctive web-like patterns in the gem. While mined in various locations, the lore and historical use of turquoise are deeply tied to regions like Egypt and the American Southwest.
Zircon is a zirconium silicate mineral that forms in igneous and metamorphic rocks. It is a durable mineral that can survive geological processes, making it one of the oldest materials on Earth. The brilliant blue zircon used in jewelry is typically achieved by heating brown zircon crystals to high temperatures, a process that can also enhance its clarity. This treatment is standard in the industry and produces the coveted blue hue that makes it a December birthstone.
Blue topaz is a silicate mineral composed of aluminum and fluorine. Its color, which ranges from light sky blue to deep London blue, is almost always the result of treatment. Natural blue topaz is exceedingly rare; most commercial blue topaz is produced by irradiating naturally colorless topaz, followed by heat treatment to stabilize the color and achieve the desired shade. This gemstone is mined in several countries, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States. Its geological formation involves the crystallization of magma or the metamorphism of rocks, but the vibrant blues prized by jewelers are a product of human ingenuity in gemology.
Tanzanite is a variety of the mineral zoisite and is prized for its rich violet-blue to deep blue color, which exhibits pleochroism—showing different colors when viewed from different angles. Its formation is geologically unique; it is found in only one place on Earth: a small, four-square-kilometer mining area in the Merelani Hills of Tanzania, near the base of Mount Kilimanjaro. This extreme rarity, with all known commercial deposits confined to this single location, is the primary reason for its high value and cost. The gem forms through a complex metamorphic process involving heat and pressure acting on specific mineral formations in the region.
Gemological Properties
Understanding the physical and chemical properties of each gemstone is crucial for both appreciation and practical care. The following table summarizes key gemological data for the four December birthstones, as derived from the provided sources.
| Gemstone | Color & Varieties | Mohs Hardness | Chemical Composition | Key Properties |
|---|---|---|---|---|
| Turquoise | Blue to green, often opaque with matrix | 5 – 6 | Hydrated phosphate of copper and aluminum | Semi-translucent to opaque; distinctive matrix patterns. |
| Tanzanite | Violet-blue to deep blue (pleochroic) | 6 – 7 | Calcium aluminum hydroxyl silicate | Pleochroic, showing blue, violet, and burgundy tones. |
| Blue Topaz | Sky Blue, Swiss Blue, London Blue | 8 | Aluminum silicate with fluorine and hydroxyl groups | Silicate mineral; most commercial stones are irradiated and heat-treated. |
| Zircon | Brilliant blue (also multi-color) | 6.5 – 7.5 | Zirconium silicate | High refractive index and dispersion ("fire"); blue color typically from heat treatment. |
Turquoise has a Mohs hardness of 5 to 6, making it relatively soft and susceptible to scratching and chemical damage. Its opacity and characteristic matrix are defining features, and it is often used in cabochon cuts rather than faceted gems. Tanzanite is slightly harder, with a Mohs hardness of 6 to 7, but it is still considered fragile for rings due to its perfect cleavage in one direction, which makes it vulnerable to impact. It is most often set in protective settings for earrings and pendants. Blue topaz is the hardest of the four, with a Mohs hardness of 8, making it durable enough for daily wear in rings. However, its deep cleavage means it can still be chipped if struck with force. Zircon has a Mohs hardness between 6.5 and 7.5, making it more durable than turquoise or tanzanite, though still softer than blue topaz. It is prized for its brilliance and fire, which rival those of diamonds, and is often faceted to maximize its light performance.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each December birthstone carries a legacy of symbolic meaning and metaphysical belief. Turquoise is overwhelmingly associated with protection, healing, and good fortune. Its lore as a guardian against falls and disaster, and as a bringer of wealth and health, spans continents and centuries, from ancient Egypt to the American Southwest. It is also linked to friendship and emotional balance.
Tanzanite, as a modern discovery, has been attributed with meanings of transformation, intuition, and spiritual growth. Its unique color shift and single-source rarity contribute to its symbolism of new beginnings and a deeper connection to one's inner self.
Blue topaz is symbolically tied to clarity, communication, and calmness. Its clear, blue hues evoke serenity and truth, making it a popular choice for those seeking to enhance clear thought and peaceful expression.
Zircon is associated with wisdom, prosperity, and good fortune. Its brilliant clarity and fire are thought to inspire mental clarity and attract success, making it a stone for those who value intellect and balance.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, and it must be tailored to their specific properties. Turquoise, being the softest (Mohs 5-6) and porous, is highly susceptible to damage from chemicals, heat, and even prolonged exposure to skin oils and lotions, which can cause discoloration. It should be cleaned only with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaning, and harsh chemicals. Store it separately to prevent scratching.
Tanzanite (Mohs 6-7) requires gentle handling due to its perfect cleavage. It should never be subjected to ultrasonic cleaners or steam, as vibrations and heat can cause fractures. Cleaning with warm, soapy water and a soft brush is safe, but it must be handled with care to avoid knocks. Its fragility makes protective settings advisable for rings.
Blue topaz (Mohs 8) is more durable but still has deep cleavage. It is generally safe to clean with warm, soapy water and a soft brush. While it can withstand mild chemicals, it is best to avoid prolonged exposure. Ultrasonic cleaning is usually acceptable for stable stones, but caution is advised if the stone has inclusions or fractures.
Zircon (Mohs 6.5-7.5) is relatively durable but can be brittle. It is best cleaned with warm, soapy water and a soft brush. Ultrasonic cleaners are generally not recommended due to the risk of fracturing the stone, especially if it has been heat-treated. Avoid sudden temperature changes.
Conclusion
The four December birthstones—turquoise, tanzanite, zircon, and blue topaz—offer a remarkable diversity within a cohesive color theme. From the ancient, protective turquoise to the modern, transformative tanzanite, each stone tells a unique story of geological formation, historical significance, and cultural symbolism. Their gemological properties vary widely, from the soft, opaque turquoise to the hard, brilliant blue topaz, providing options for every preference and lifestyle. This variety is what makes December's birthstone selection particularly special, allowing individuals to choose a gem that resonates not only with their birth month but also with their personal style, values, and practical needs. Whether one is drawn to the lore of antiquity, the rarity of a single-source gem, or the durability of a modern classic, the blue jewels of December provide a wealth of choices for collectors and jewelry lovers alike.