The month of December is uniquely associated with three distinct birthstones: turquoise, tanzanite, and zircon. This triad offers a remarkable spectrum of color, from the sky-blue of turquoise to the violet-blue of tanzanite and the fiery brilliance of zircon. Each stone possesses its own geological origin, historical narrative, and gemological identity, providing December-born individuals with a rich palette of choices. This article explores the properties, histories, and significance of these three gemstones, drawing exclusively from the provided source materials.
History and Lore
The historical journey of December's birthstones is marked by both ancient tradition and modern discovery. Turquoise stands as the most ancient of the three, with a legacy that spans millennia.
Turquoise: An Ancient Talisman Turquoise has been prized for over 6,000 years. The provided sources indicate that it is one of the earliest gems to be mined and used for ornamentation. Its name is derived from the French word pierre turquoise, meaning "Turkish stone," reflecting the historical trade routes through which it reached Europe from mines in Persia (modern-day Iran). For centuries, it was believed to possess protective qualities. Many cultures, including ancient Egyptian, Persian, and Native American societies, regarded turquoise as a sacred stone that could ward off evil and bring good fortune. It was often used in ceremonial objects, jewelry, and even as a protective covering for the eyes in burial masks. The stone's association with protection and well-being is a recurring theme in historical lore.
Tanzanite: A Modern Marvel In stark contrast to turquoise's ancient history, tanzanite is a gemstone of the 20th century. It was not known to the gemological world until 1967. Its discovery is attributed to a Masai tribesman who found blue crystals in the Merelani Hills of northern Tanzania. Initially mistaken for sapphire, the stone was later identified as a variety of the mineral zoisite. The name "tanzanite" was coined by Tiffany & Co., which recognized its potential and launched a major marketing campaign in 1968, bringing it to global prominence. Due to its limited geographic origin—it is found in only one location worldwide—tanzanite is often described as "a thousand times rarer than diamond." Its rapid rise to fame makes it a true modern classic, lacking the ancient myths of turquoise but rich in contemporary symbolism.
Zircon: The "Stone of Honor" Zircon is one of the oldest minerals on Earth, with zircon crystals found in Australian rocks dating back over 4.4 billion years. However, as a gemstone, its history is often confused due to its similarity to cubic zirconia, a synthetic material. The provided sources clarify that natural zircon has been used in jewelry for centuries, valued for its exceptional brilliance and fire. In the Middle Ages, it was believed to promote honor, purity, and wisdom. It was also thought to aid in sleep and bring prosperity. Its high refractive index and strong dispersion (fire) made it a popular diamond simulant before the advent of modern synthetics. Today, it is celebrated as a traditional December birthstone, offering an affordable yet dazzling alternative to more expensive gems.
Geological Formation and Sources
Each of these gemstones forms under distinct geological conditions and is sourced from specific regions of the world.
Turquoise: A Hydrated Mineral Turquoise is not a silicate gemstone like most others; it is a hydrated phosphate of copper and aluminum. It forms in arid regions where acidic, copper-rich groundwater seeps through rocks containing aluminum and phosphorus. Over time, these minerals crystallize into nodules and veins. The most significant historical sources include Iran (Persia), which produced the prized "Persian turquoise" known for its uniform sky-blue color, and the Southwestern United States (Arizona, New Mexico, Nevada), where Native American tribes have mined and worked with turquoise for centuries. Other notable sources mentioned in the materials include Egypt, China, and Tibet. The color of turquoise is directly influenced by its copper content (for blue) and iron content (for greenish hues).
Tanzanite: A Single-Source Gemstone Tanzanite's geological story is unique. It forms from the alteration of zoisite under intense heat and pressure, a process linked to the tectonic activity that formed the East African Rift. The only known source of gem-quality tanzanite is a small, four-square-kilometer mining area in the Merelani Hills near Mount Kilimanjaro in Tanzania. This extreme rarity is a key factor in its value. The crystals are typically found in pegmatite veins and alluvial deposits. Due to its limited occurrence, the supply of tanzanite is finite, making it a gemstone of increasing scarcity.
Zircon: A High-Temperature Mineral Zircon (zirconium silicate, ZrSiO₄) is a common mineral in igneous and metamorphic rocks. Gem-quality zircon is found in placer deposits, where it has been eroded from its host rock and concentrated by water or wind action. Major sources include Cambodia (for brownish zircon), Sri Lanka (for a variety of colors), and Australia (where it is often found as a byproduct of mining for other minerals like opals). Australian zircon is particularly notable for being one of the oldest minerals on the planet, with crystals dating back billions of years. Zircon forms in high-temperature environments, such as magmatic rocks and metamorphic settings, which contributes to its durability and crystal clarity.
Gemological Properties
Understanding the physical and optical properties of these stones is essential for identification, valuation, and care.
Turquoise
Turquoise is prized for its opaque, waxy appearance. Its key properties include: * Chemical Formula: CuAl₆(PO₄)₄(OH)₈·4H₂O (a hydrated copper-aluminum phosphate). * Hardness (Mohs Scale): 5 to 6. This makes it relatively soft and susceptible to scratching, requiring careful handling. * Crystal System: Triclinic. * Refractive Index: Approximately 1.61 to 1.65 (unusually low for an opaque gem). * Specific Gravity: 2.60 to 2.90. * Luster: Waxy to subvitreous. * Key Characteristic: It is often porous and can be treated (stabilized) with resins or waxes to enhance its durability and color. Natural, untreated turquoise is rare and valuable.
Tanzanite
Tanzanite is a transparent to translucent variety of zoisite. Its properties are distinctive: * Chemical Formula: Ca₂Al₃(SiO₄)₃(OH) (a calcium aluminum silicate hydroxide). * Hardness (Mohs Scale): 6 to 7. It is durable enough for most jewelry but can be brittle. * Crystal System: Orthorhombic. * Refractive Index: 1.691 to 1.700. * Specific Gravity: 3.35. * Luster: Vitreous (glass-like). * Key Characteristic: Its most famous property is its strong trichroism—showing three different colors (blue, violet, and reddish-brown) when viewed from different crystal directions. Most tanzanite is heat-treated to achieve its signature blue-violet color.
Zircon
Zircon is renowned for its brilliance and fire, often rivaling diamond. * Chemical Formula: ZrSiO₄ (zirconium silicate). * Hardness (Mohs Scale): 6.5 to 7.5. It is quite durable for jewelry. * Crystal System: Tetragonal. * Refractive Index: 1.92 to 2.01 (high, contributing to its brilliance). * Specific Gravity: 4.6 to 4.7 (high). * Dispersion: 0.039 (high, giving it strong "fire"). * Luster: Adamantine (brilliant). * Key Characteristic: High refractive index and dispersion. It is important to distinguish natural zircon from synthetic cubic zirconia (CZ), which is a different material altogether.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these stones carry deep symbolic meanings.
Turquoise: Protection and Healing As one of the oldest protective amulets, turquoise is universally associated with protection, good fortune, and healing. It is believed to promote calm, balance, and emotional stability. In many cultures, it is considered a conduit for spiritual energy, helping to align the chakras and foster communication. Its connection to the sky and water makes it a symbol of tranquility and renewal.
Tanzanite: Transformation and Intuition Given its modern discovery, tanzanite's metaphysical associations are more contemporary. It is often called the "stone of transformation" and is believed to facilitate spiritual growth, psychic abilities, and higher consciousness. Its striking color is associated with the throat and third-eye chakras, promoting clear communication and intuitive insight. Some believe it helps in understanding one's destiny and making positive life changes.
Zircon: Wisdom and Prosperity Zircon has long been associated with wisdom, honor, and purity. It is believed to enhance self-confidence, promote spiritual growth, and attract prosperity. In some traditions, it is used as a protective stone that wards off negative energy and fosters a sense of security. Its brilliant fire is said to inspire creativity and clarity of thought.
Care and Cleaning
Proper maintenance is crucial to preserve the beauty and integrity of these gemstones, especially given their varying hardness levels.
Turquoise Care Due to its low hardness (5-6) and porous nature, turquoise requires gentle care. It should be cleaned with a soft, dry cloth. Avoid exposure to chemicals, including perfumes, lotions, and cleaning agents, which can damage its surface and cause discoloration. It is also susceptible to cracking from sudden temperature changes. Stabilized turquoise is more durable but still needs careful handling. It is best to store turquoise jewelry separately to prevent scratching by harder gems.
Tanzanite Care With a hardness of 6 to 7, tanzanite is relatively durable but can be brittle. It is safe to clean with warm, soapy water and a soft brush. Ultrasonic and steam cleaners should be avoided, as the vibrations and heat can cause fractures. It is advisable to remove tanzanite jewelry during strenuous activities to prevent impact damage. Due to its trichroism, it is often cut to maximize its blue-violet color, so protecting the stone from sharp blows is important.
Zircon Care Zircon's hardness of 6.5 to 7.5 makes it suitable for most jewelry, but it can be brittle and prone to chipping if struck. Cleaning is straightforward: use warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as they may cause fractures in stones with inclusions. Zircon should be stored carefully to prevent scratching by other gems. Its high refractive index means it can appear dirty more quickly, so regular gentle cleaning is recommended.
Conclusion
The birthstones of December—turquoise, tanzanite, and zircon—offer a captivating journey through time, geology, and human culture. Turquoise carries the weight of ancient history and protective lore, its opaque blue-green hue a testament to its enduring appeal. Tanzanite, a gem of recent discovery, dazzles with its vivid color and represents the thrill of the new and the rare. Zircon, the oldest of the three, combines remarkable durability with a brilliance that rivals the most coveted of gems. Together, they provide a diverse and meaningful selection for those born in the final month of the year, each stone telling a unique story of formation, discovery, and symbolic power.