In the realm of gemology, few months offer a more vibrant and diverse palette than December. While many months are associated with a single gemstone, December is uniquely celebrated with three distinct birthstones: turquoise, tanzanite, and zircon. This trio represents a remarkable spectrum of color, from the ancient sky-blue of turquoise to the electric violet-blue of tanzanite and the brilliant, multifaceted fire of zircon. Each stone carries its own profound history, geological narrative, and symbolic weight, making December a month of exceptional choice for those seeking personal adornment. This article delves into the detailed characteristics, origins, and cultural significance of these three celebrated gemstones, providing a comprehensive guide for enthusiasts, collectors, and anyone interested in the science and lore behind their birthstone.
The modern list of birthstones was largely standardized in 1912 by the National Association of Jewelers, with subsequent updates. December's trio reflects this evolution, incorporating both ancient and modern gems. Turquoise is one of the oldest known gemstones, with a history spanning millennia. Tanzanite, a relative newcomer to the gem world, was only discovered in the 20th century. Zircon, often confused with cubic zirconia, is one of the oldest minerals on Earth, with crystals dating back billions of years. Together, they offer a unique intersection of geological time, human history, and aesthetic appeal. Understanding each stone's properties, from its chemical composition to its cultural lore, allows for a deeper appreciation of their role as December's birthstones.
History and Lore: A Journey Through Time
The historical narratives of December's birthstones are as varied as their colors. Turquoise holds the distinction of being the most ancient, with evidence of its use dating back to ancient Egypt, where it was worn as a protective amulet and inlaid into the iconic funeral mask of Tutankhamun. The stone's name is derived from the French "pierre turquoise," meaning "Turkish stone," as it was brought to Europe from Persia via Turkish traders. In many cultures, turquoise has been revered as a stone of protection, believed to ward off evil and bring good fortune. Native American tribes, particularly the Navajo, Zuni, and Pueblo peoples, have a deep spiritual connection to turquoise, incorporating it into intricate silver jewelry and viewing it as a living stone that connects the wearer to the earth and sky.
Tanzanite's history is remarkably brief but dramatic. It was first identified in the 1960s in the Merelani Hills of Tanzania, near the foot of Mount Kilimanjaro. Initially, the blue zoisite crystals were overlooked, but a 1967 discovery by a local Maasai hunter brought them to the attention of international gemologists. The Tiffany & Co. jewelry house, recognizing its unique beauty, launched a marketing campaign in 1968, naming the gemstone "tanzanite" after its country of origin and promoting it as a once-in-a-lifetime discovery. Its rapid ascent to prominence is a testament to the power of marketing and its undeniable visual appeal, which led to its official adoption as a December birthstone in 2002.
Zircon's history is long and often misunderstood. It is one of the oldest minerals on Earth, with zircon crystals found in Australia dating back over 4.4 billion years. However, its name is frequently confused with the synthetic material "cubic zirconia" (CZ), which is a diamond simulant. This confusion has unfortunately tarnished the reputation of natural zircon, a genuinely precious gemstone. Historically, zircon was believed to promote sleep, ward off evil, and bring prosperity and honor. In the Middle Ages, it was thought to aid in restful sleep and protect travelers. Despite its ancient origins and historical significance, zircon remains one of the most underappreciated gemstones in the modern market, often overlooked due to its name association.
Geological Formation and Sources
The geological origins of these three gemstones are fundamentally different, contributing to their unique properties and values.
Turquoise is a secondary mineral that forms in the near-surface environment. It is a hydrated phosphate of copper and aluminum, requiring the presence of copper and acidic water percolating through aluminum-rich rocks like weathered volcanic ash or sedimentary deposits. The most famous turquoise deposits are found in the arid regions of the American Southwest (Arizona, New Mexico, Nevada), Iran (Persia), Egypt, and Tibet. The quality of turquoise is heavily influenced by its matrix—the host rock that becomes part of the gem. For example, the renowned "Spiderweb" turquoise from the Nevada mines features a distinctive black or brown web-like pattern within the blue stone. Iranian turquoise is prized for its uniform, sky-blue color with little to no matrix, while Chinese turquoise often exhibits a greener hue due to higher iron content.
Tanzanite is a variety of the mineral zoisite. It is a calcium aluminum silicate hydroxide mineral, specifically a gemological variety of zoisite. Its formation is extraordinarily rare, requiring a unique combination of geological conditions that are believed to have occurred only in a small, four-square-kilometer area in the Merelani Hills of Tanzania. The process involves the metamorphism of the host rock under high heat and pressure, which introduces vanadium and chromium, elements that give the stone its signature blue and violet hues. The primary and currently the only commercial source of tanzanite is in the Merelani Hills, making it a single-source gemstone. This geographic rarity adds to its value and allure.
Zircon is a zirconium silicate (ZrSiO₄) and is one of the first minerals to crystallize as magma cools. It is a primary mineral found in igneous and metamorphic rocks. Its remarkable durability and resistance to chemical and physical change allow it to survive billions of years of geological processes. Zircon is mined from placer deposits (gravels, sands) as well as from hard-rock mines. Major sources include Australia (the leading producer), Thailand, Cambodia, Sri Lanka, and the United States (specifically the gem gravels of the North Carolina mountains). Australian zircon often produces brownish crystals, which are then heat-treated to achieve a colorless or blue hue. The stone's high refractive index and strong fire make it a brilliant gem when cut properly.
Gemological Properties
A scientific understanding of each gemstone's properties is essential for identification, valuation, and care. The following table summarizes key gemological data for December's birthstones, based on established gemological standards.
| Property | Turquoise | Tanzanite | Zircon |
|---|---|---|---|
| Chemical Composition | CuAl₆(PO₄)₄(OH)₈·4H₂O | Ca₂Al₃(SiO₄)₃(OH) | ZrSiO₄ |
| Crystal System | Triclinic | Orthorhombic | Tetragonal |
| Hardness (Mohs Scale) | 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 |
| Typical Treatments | Stabilization (wax/resin), dyeing | Heat (to enhance blue color) | Heat (to change color), irradiation |
| Notable Characteristics | Often porous; shows matrix; color can fade with prolonged sun exposure. | Pleochroism (shows different colors from different angles); heat treatment is standard and accepted. | Strong dispersion (fire) greater than diamond; high refractive index. |
Turquoise is the softest and most delicate of the trio. Its hardness ranges from 5 to 6 on the Mohs scale, making it susceptible to scratching and abrasion. Most turquoise on the market today is treated to enhance its stability and color. Stabilization involves impregnating the porous stone with a clear wax, resin, or polymer to harden it and prevent color change. This is a standard and accepted industry practice. Natural, untreated turquoise is rare and commands a premium. The presence of a matrix (host rock) is a natural characteristic and does not inherently indicate lower quality, though the aesthetic appeal of the matrix pattern is a matter of personal taste.
Tanzanite has a hardness of 6.5 to 7, making it suitable for most jewelry, though it should be protected from hard blows. Its most notable optical property is strong pleochroism, meaning it can display three different colors: blue, violet, and burgundy, depending on the crystal orientation. Gem cutters must carefully orient the rough crystal to present the desired blue-violet hue. Virtually all tanzanite on the market has been heat-treated to remove the brownish-yellow component and enhance the desirable blue and violet colors. This treatment is permanent and is considered standard practice; untreated tanzanite is extremely rare.
Zircon is a highly durable gemstone with a hardness of 6.5 to 7.5, making it resistant to scratching and suitable for all types of jewelry, including rings. Its most spectacular optical property is its high dispersion (0.039), which is greater than that of a diamond (0.044), giving it exceptional fire—the ability to split light into spectral colors. Combined with a high refractive index (1.925-2.015), zircon can display a brilliant sparkle that rivals diamond. However, its hardness is offset by a tendency toward brittleness and perfect cleavage in one direction, requiring careful cutting and setting. Most brownish zircon is heat-treated to produce colorless or blue stones. Heat treatment is stable and permanent, but zircon is also sensitive to prolonged exposure to high temperatures (above 500°C), which can alter its color or cause cracking.
Symbolism and Metaphysical Beliefs
Beyond their physical properties, each of December's birthstones carries a rich tapestry of symbolic meaning and metaphysical belief.
Turquoise is universally regarded as a stone of protection, healing, and tranquility. It is often called the "Master Healer" and is believed to align all chakras, stabilize mood, and promote inner peace. In many cultures, it is a talisman for travelers, said to protect against accidents and falls. Its connection to the sky and water makes it a symbol of spiritual grounding and clarity. The stone is also associated with wisdom, truth, and courage, and is often given as a symbol of friendship and good fortune.
Tanzanite, being a modern discovery, has developed a more contemporary set of metaphysical associations. It is often linked to transformation and new beginnings, reflecting its rapid rise to prominence. It is believed to stimulate the throat and third-eye chakras, enhancing communication, intuition, and spiritual awareness. Some crystal healers attribute tanzanite with the ability to facilitate a connection to higher spiritual realms and to promote a sense of calm and tranquility, helping to alleviate stress and anxiety.
Zircon has a long history of metaphysical associations, primarily linked to its durability and brilliance. It is believed to promote honor, purity, and dignity. Historically, it was thought to aid in restful sleep and protect against bad dreams. In modern crystal healing, clear zircon is associated with clarity of thought and spiritual grounding, while blue zircon is linked to peace and tranquility. It is also believed to enhance self-confidence and attract prosperity and success. Its fiery brilliance is often connected to the spark of creativity and inspiration.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, and their care requirements differ significantly due to their varying physical properties.
Turquoise, with its lower hardness and porous nature, requires gentle handling. It should be protected from chemicals, including perfumes, lotions, and household cleaners, which can damage or discolor the stone. Cleaning should be done with a soft, damp cloth and mild soap, avoiding ultrasonic and steam cleaners, which can cause cracking or discoloration. It is best to store turquoise jewelry separately to prevent scratching by harder stones. Prolonged exposure to direct sunlight should be avoided, as it can cause the color to fade over time.
Tanzanite is relatively durable but should be handled with care due to its cleavage planes and sensitivity to heat. It is susceptible to scratching, so it should be stored separately from other jewelry. Cleaning can be done with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaners, as the vibrations and heat can cause fractures. It is also advisable to remove tanzanite jewelry during physical activities to prevent impact damage.
Zircon, despite its hardness, is brittle and has perfect cleavage, making it vulnerable to chipping or cracking from a sharp blow. It should be handled with care and stored in a soft cloth or separate compartment to avoid damage from harder gems like diamonds. Cleaning is straightforward with warm, soapy water and a soft brush. However, zircon should never be exposed to high heat or sudden temperature changes, as this can cause internal fractures or color change. Ultrasonic cleaners are generally safe for zircon, but caution is advised for stones with visible inclusions or fractures.
Conclusion
The birthstones of December—turquoise, tanzanite, and zircon—offer a compelling study in contrast. From the ancient, earthy turquoise to the modern, vibrant tanzanite and the ancient, fiery zircon, each stone provides a unique avenue for personal expression and connection to the natural world. Their distinct geological origins, from secondary phosphate deposits to rare metamorphic formations and billion-year-old crystals, underscore the incredible diversity of our planet's mineral kingdom. While turquoise boasts millennia of cultural history and protective lore, tanzanite captivates with its recent discovery and dramatic color, and zircon astounds with its ancient origins and diamond-like fire. Understanding their gemological properties and proper care ensures that these stones can be enjoyed for generations. Whether chosen for their aesthetic beauty, historical significance, or symbolic meaning, December's trio of birthstones provides an unparalleled selection for collectors, jewelers, and anyone born in the final month of the year.