The final month of the year is uniquely blessed with a trio of exceptional birthstones: tanzanite, turquoise, and zircon. Each gemstone offers a distinct spectrum of color, history, and geological origin, providing a rich palette for those born in December. From the vibrant blues of tanzanite to the ancient sky-tone of turquoise and the brilliant fire of zircon, these stones have captivated humanity for centuries. This article delves into the fascinating world of these December birthstones, exploring their gemological properties, historical journeys, and the cultural significance that makes them enduring favorites in jewelry and lore. We will examine each stone individually, uncovering the science behind their beauty and the stories that have elevated them to their status as modern birthstones.
Tanzanite: The Blue-Violet Marvel from a Single Source
Among the three December birthstones, tanzanite is the most recent addition, both geologically and historically. Discovered in the late 20th century, this gemstone’s story is one of serendipity and rapid ascent to gemstone royalty.
History and Discovery
Tanzanite’s history is remarkably brief. It was first identified in 1967 by a Tanzanian prospector named Manuel de Souza near the Merelani Hills of Mount Kilimanjaro. Initially mistaken for a different mineral, it was later confirmed to be a variety of the mineral zoisite. The gem was named tanzanite in 1968 by Tiffany & Co., which recognized its potential and became the primary distributor. The company marketed it as "the most beautiful blue stone discovered in 2,000 years," a claim that, while hyperbolic, speaks to its striking color. Its status as a birthstone was formalized in 2002 when the American Gem Trade Association (AGTA) added it to the official list, making it one of the few stones with a designated "modern" birthstone designation.
Geological Formation and Sources
Tanzanite’s geological rarity is a key part of its allure. It is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This small, roughly 4-square-kilometer area is the exclusive source of gem-quality tanzanite. The stone forms in the presence of heat and pressure from metamorphic processes, specifically in the presence of vanadium and chromium, which are responsible for its unique color. The mining process is challenging, and the finite nature of the deposit has led to comparisons with other single-source gems like diamonds from Golconda or emeralds from Muzo.
Gemological Properties
Tanzanite is a variety of the mineral zoisite, with a chemical formula of Ca₂Al₃(SiO₄)₃(OH). It is a relatively soft stone, registering 6.5 to 7 on the Mohs scale of hardness, which makes it suitable for jewelry but requires careful handling to avoid scratches. Its most defining characteristic is its pleochroism—the ability to display different colors when viewed from different crystal directions. In its typical form, tanzanite shows blue, violet, and burgundy hues. The most valued color is a deep, saturated blue-violet, often achieved through a heat treatment process that removes the brownish tones naturally present in most rough material. This treatment is standard and accepted in the trade, as it stabilizes the color and enhances the stone's beauty.
Symbolism and Metaphysical Beliefs
While its history is modern, tanzanite has quickly accumulated metaphysical associations. It is often linked to spiritual awakening and communication, believed to open the throat and third-eye chakras. Some wearers attribute to it the power to facilitate a connection with higher consciousness and to promote a calm, meditative state. Its striking color is also associated with transformation, mirroring its own geological journey from the earth’s depths to the light.
Care and Cleaning
Given its moderate hardness, tanzanite should be protected from rough wear. It is best suited for earrings, pendants, and occasional-wear rings. Cleaning can be done with warm, soapy water and a soft brush. Ultrasonic and steam cleaners are not recommended, as the stone’s inclusions or any potential fractures could be aggravated by the vibrations and heat. Storing tanzanite separately from harder gemstones will prevent scratching.
Turquoise: The Ancient Sky Stone
Turquoise is arguably the oldest gemstone in human history, with a legacy spanning millennia and continents. Its name derives from the French pierre turquoise, meaning "Turkish stone," reflecting its historical trade route from Persia to Europe via Turkey. It is a hydrated phosphate of copper and aluminum, prized for its distinctive sky-blue to greenish-blue color.
History and Lore
Turquoise has been mined and revered for over 5,000 years. Evidence of its use has been found in ancient Egyptian tombs, where it was used in elaborate jewelry and amulets, such as the famous burial mask of Tutankhamun. The Persians called it pirouzeh, meaning "victory," and believed it protected the wearer from unnatural death. In the Americas, Native American tribes, particularly the Navajo, Zuni, and Pueblo peoples, have a profound connection to turquoise. It is considered a sacred stone, a piece of the sky that fell to earth, and is integral to their spiritual and ceremonial practices. Its status as a birthstone is long-standing; it is traditionally associated with December, alongside zircon and, more recently, tanzanite.
Geological Formation and Sources
Turquoise is not a single mineral but a hydrous phosphate of copper and aluminum that forms in arid regions where acidic, copper-rich water percolates through rocks containing aluminum and phosphorus. This process occurs over millions of years, creating nodules or veins. Major sources include the United States (particularly Arizona and New Mexico), Iran (the historical source of the finest "Persian turquoise"), China, and Egypt. The color is directly tied to its chemical composition: higher copper content yields a bluer hue, while iron and zinc can create greenish tones. The matrix—the host rock in which the turquoise forms—adds to its character, with examples like "spiderweb" matrix from Nevada being highly prized.
Gemological Properties
Turquoise has a hardness of 5 to 6 on the Mohs scale, making it relatively soft and porous. It often contains inclusions and matrix, which are considered part of its natural beauty. Its specific gravity ranges from 2.6 to 2.9, and it is typically opaque. Due to its porosity, turquoise is often stabilized with resins or waxes to enhance durability and color, a common and accepted practice. Natural, untreated turquoise is rare and commands a premium. The stone’s color can fade with prolonged exposure to sunlight, chemicals, or body oils, which is why it is often sealed.
Symbolism and Metaphysical Beliefs
Turquoise is universally associated with protection, healing, and good fortune. It is believed to ward off negative energy, promote emotional balance, and bring peace of mind. In many cultures, it is considered a talisman for travelers, offering safety on journeys. Its connection to the sky and water links it to clarity of thought, communication, and spiritual attunement. For many Native American cultures, it is a stone of the earth and sky, embodying the balance between the physical and spiritual realms.
Care and Cleaning
Turquoise requires careful maintenance. It should be cleaned with a soft, damp cloth and mild soap, then dried thoroughly. Avoid harsh chemicals, including perfumes, lotions, and household cleaners, as they can damage the stone. Ultrasonic and steam cleaners are strictly prohibited. To prevent color fading, store turquoise away from direct sunlight. Periodic re-polishing may be needed for pieces that are worn frequently.
Zircon: The Fire and Brilliance of December
Often confused with the synthetic cubic zirconia, natural zircon is one of the oldest minerals on Earth, with crystals dating back over 4 billion years. It is a zirconium silicate (ZrSiO₄) and is prized for its exceptional brilliance and fire, which rival that of diamond.
History and Lore
Zircon has a long and storied history. The word "zircon" may derive from the Persian zargun, meaning "gold-colored," though today’s most valued color is a vivid blue. In the Middle Ages, it was believed to promote rest, ward off evil spirits, and induce prosperity and honor. It was also thought to help with sleep when placed under a pillow. Blue zircon, in particular, was popular in Victorian-era jewelry. It is the traditional birthstone for December, a designation it has held for centuries. Its association with the month may stem from its brilliant, star-like appearance, reminiscent of winter constellations.
Geological Formation and Sources
Zircon forms in igneous and metamorphic rocks. It is a common mineral in granites and syenites and is also found in alluvial deposits as a durable detrital mineral. Major sources include Australia (the leading producer), Norway, France, and the United States (specifically North Carolina and the gem gravels of the Himalayas). The stone’s durability makes it resistant to weathering, which is why ancient zircon crystals are found in riverbeds and sedimentary rocks. Blue zircon, the most popular color for jewelry, is typically achieved through heat treatment of brown or yellowish zircon crystals, a process that is stable and permanent.
Gemological Properties
Zircon is a dense, hard stone, registering 6.5 to 7.5 on the Mohs scale, making it durable for all types of jewelry. Its refractive index is exceptionally high (1.92-2.01), giving it a brilliance and fire that can exceed that of diamond. It is doubly refractive, which can sometimes be observed with a loupe. The stone’s specific gravity is high (4.6-4.7), a key identifier that distinguishes it from similar-looking stones like synthetic cubic zirconia (which has a specific gravity of 5.6-6.0) or glass. Zircon is available in a variety of colors, including colorless, blue, green, yellow, brown, and red, with blue being the most sought-after for December birthstone jewelry.
Symbolism and Metaphysical Beliefs
Zircon is associated with wisdom, wealth, and honor. It is believed to enhance spiritual growth and protect the wearer. Blue zircon, in particular, is linked to clarity of thought and communication, making it a stone for speakers and leaders. Some believe it aids in meditation and helps to calm an overactive mind. Its brilliant sparkle is thought to inspire creativity and joy.
Care and Cleaning
Zircon is relatively hard but can be brittle due to its high refractive index and potential for cleavage. It should be protected from sharp blows. Cleaning is straightforward with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and sudden temperature changes, as these can cause fractures. Store zircon jewelry separately to prevent scratching other pieces.
Comparative Overview: The Three December Gems
To better understand the unique characteristics of each December birthstone, the following table summarizes their key gemological properties based on the available information.
| Property | Tanzanite | Turquoise | Zircon |
|---|---|---|---|
| Mineral Family | Zoisite | Hydrated phosphate (non-silicate) | Zirconium silicate |
| Chemical Formula | Ca₂Al₃(SiO₄)₃(OH) | CuAl₆(PO₄)₄(OH)₈·4H₂O | ZrSiO₄ |
| Hardness (Mohs) | 6.5 - 7 | 5 - 6 | 6.5 - 7.5 |
| Typical Color | Blue-violet (pleochroic) | Sky-blue to greenish-blue | Blue (most common for Dec.) |
| Key Characteristic | Pleochroism, single-source | Porosity, often matrix-included | High brilliance & fire |
| Stability | Heat-stable; sensitive to blows | Sensitive to chemicals/sunlight | Heat-stable; can be brittle |
| Primary Sources | Merelani Hills, Tanzania | USA, Iran, China, Egypt | Australia, Norway, USA |
Caring for Your December Birthstone Jewelry
While each of the December birthstones has specific care requirements, there are general principles to ensure their longevity. First, always remove jewelry before engaging in physical activities, housework, or gardening to prevent impacts and exposure to harsh chemicals. Second, store each piece separately in a soft-lined jewelry box or pouch to prevent scratches. Third, put on perfume, lotion, and hairspray before putting on your jewelry to minimize chemical contact. Finally, have your jewelry inspected by a professional jeweler annually to check for loose settings, prong wear, and overall condition.
For cleaning, a gentle approach is always best. Use a soft, lint-free cloth for a quick polish. For a deeper clean, use lukewarm water, a drop of mild dish soap, and a soft-bristled brush. Rinse thoroughly and dry completely. When in doubt, consult a gemologist or jeweler, especially for pieces with intricate settings or fragile stones.
Conclusion
The birthstones of December—tanzanite, turquoise, and zircon—offer a remarkable diversity that reflects the richness of the natural world. From the exclusive, modern allure of tanzanite to the ancient, protective power of turquoise and the brilliant, timeless fire of zircon, each stone provides a unique connection to history, geology, and personal identity. Whether chosen for their captivating colors, their storied pasts, or their symbolic meanings, these gems continue to be celebrated by those born in the final month of the year. Their enduring appeal lies in their ability to combine scientific wonder with human tradition, making them truly special treasures to be worn and cherished.