December stands uniquely among the months for its association with not one, but three distinct and celebrated gemstones: turquoise, tanzanite, and zircon. This multiplicity offers a remarkable palette of blue hues, from the serene sky blues of turquoise to the vivid violet-blue of tanzanite and the brilliant, diamond-like sparkle of zircon. Each stone carries its own deep history, geological origin, and symbolic meaning, providing a diverse array of choices for those born in the final month of the year. This article explores the gemological properties, historical lore, and cultural significance of December’s three official birthstones, delving into the science and stories that make them enduring favorites in the world of fine jewelry.
History and Lore: Ancient Talismans and Modern Discoveries
The history of December’s birthstones spans millennia, with each gemstone boasting a unique narrative that connects it to different civilizations and eras.
Turquoise is arguably the most ancient of the trio, cherished for over 6,000 years. Its use is documented in the burial sites of Egyptian pharaohs, where it was adorned in intricate jewelry and funerary masks. Chinese artisans were carving turquoise over 3,000 years ago, and it has been a cornerstone of Native American artistry for centuries, particularly among the Apache and Navajo peoples, who believed it held protective powers. The stone’s name itself derives from the French pierre turquoise, meaning "Turkish stone," as it was imported into Europe from Persia through Turkish trade routes. Historically, turquoise was considered a powerful talisman. It was believed to guarantee health, good fortune, and protection from harm. A widespread medieval European superstition held that the stone would break or change color to warn its wearer of impending danger or illness. Hindu mystics associated it with wealth, believing that seeing a turquoise after beholding the new moon would ensure fantastic riches.
Tanzanite, in stark contrast, is a gemstone of the modern age. It was first discovered in the late 1960s in the Merelani Hills of Tanzania, East Africa. Its rapid rise to prominence was facilitated by the Tiffany & Co. jewelry house, which recognized its extraordinary beauty and began marketing it in 1968. The gemstone was named after its country of origin, Tanzania, and its status as a December birthstone was officially recognized by the American Gem Trade Association (AGTA) in 2002. While it lacks the ancient history of turquoise, tanzanite has quickly developed its own lore, often associated with transformation, spiritual growth, and new beginnings. Its discovery in a single known location on Earth has contributed to its allure and perceived rarity.
Zircon is one of the oldest minerals on Earth, with zircon crystals found in Australia dating back over 4.4 billion years. However, as a gemstone, its history is long and sometimes misunderstood. For centuries, blue zircon was a popular gem in the Victorian era, often set in jewelry alongside diamonds. It is important to note that zircon is a natural gemstone, distinct from cubic zirconia (CZ), a synthetic diamond simulant. The confusion between the two names has sometimes led to the undervaluation of natural zircon, which possesses exceptional brilliance and fire due to its high refractive index. Historically, zircon has been associated with wisdom, prosperity, and honor. It was believed to promote sound sleep and ward off evil spirits. Its inclusion as a traditional December birthstone alongside turquoise is well-established, and its durability makes it a practical choice for various jewelry applications.
Geological Formation and Sources
Understanding where these gemstones originate reveals the geological processes that create their unique beauty and explains their geographic distribution.
Turquoise is a hydrated phosphate mineral composed of copper and aluminum. It forms in arid regions where acidic, copper-rich groundwater percolates through rocks containing aluminum and phosphorus. Over long periods, this interaction creates nodules and veins of turquoise. The gem is almost always found in a matrix of the host rock, which can be sandstone, limestone, or shale. This matrix, often a dark web-like pattern, is a key identifier of natural turquoise and contributes to its distinctive character. Major sources include the United States (particularly Arizona, New Mexico, and Nevada), Iran (historically the source of the finest "Persian turquoise"), and China. The color of turquoise ranges from sky blue to greenish hues, influenced by the specific mineral content of the host rock and the presence of iron or zinc.
Tanzanite is a variety of the mineral zoisite and owes its vivid color to trace amounts of vanadium. It is found exclusively in the Merelani Hills of Tanzania, a small mining area near the base of Mount Kilimanjaro. The formation of tanzanite is linked to a unique geological event: the intense heat and pressure from tectonic plate movement in the East African Rift. This process transformed zoisite into tanzanite. The gemstone is typically found in tabular crystals or as veins within the host rock. Due to its single-source location, tanzanite is considered more rare than diamond, and its supply is finite, adding to its value and desirability.
Zircon is a zirconium silicate mineral that forms in igneous and metamorphic rocks. It is a common accessory mineral found in many rock types, but gem-quality crystals are rarer. Zircon crystals grow in magma chambers deep within the Earth's crust and are later brought to the surface through volcanic activity or erosion. Major sources of gem zircon include Australia (particularly from the Murray Basin and the Harts Range), Cambodia, Sri Lanka, and Myanmar. The blue color in zircon is typically achieved through heat treatment of brown or yellowish-brown crystals, a common and stable enhancement that reveals the stone's brilliant blue hue.
Gemological Properties: A Scientific Profile
The value, durability, and care of each gemstone are directly tied to its physical and chemical properties. The following table summarizes the key gemological characteristics of December's three birthstones, based on data from authoritative gemological sources.
| Gemstone | Chemical Composition | Mohs Hardness | Refractive Index | Typical Treatments | Notable Optical Properties |
|---|---|---|---|---|---|
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 – 6 | 1.61 – 1.65 | Stabilization (impregnation with resin or wax) is common to enhance durability and color. | Opaque to semi-translucent; often contains a matrix (host rock). |
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | 6 – 7 | 1.69 – 1.70 | Heating is standard to remove brownish hues and produce the desirable blue/violet color. | Strong pleochroism – shows three different colors (blue, violet, red) from different angles. |
| Zircon | ZrSiO₄ | 6.5 – 7.5 | 1.92 – 1.98 (high) | Heat treatment is common to produce blue, yellow, or clear colorless varieties. | High refractive index and strong dispersion (fire) give it exceptional brilliance, rivaling diamond. |
Turquoise is the softest of the three, with a hardness of 5 to 6 on the Mohs scale. This makes it susceptible to scratching and wear, especially in rings or bracelets exposed to daily impact. Its porosity means it can absorb oils and chemicals, which may alter its color over time. For this reason, turquoise is often stabilized—a process where the stone is impregnated with a clear resin or wax—to improve its durability and luster.
Tanzanite has a moderate hardness of 6 to 7. While harder than turquoise, it is still considered delicate for rings intended for daily wear, especially in settings that expose the stone to knocks. Its most captivating feature is pleochroism. When a faceted tanzanite is rotated, an observer can see it shift from a vibrant blue to a rich violet and even to a reddish hue, depending on the crystal axis. This property is a hallmark of the stone and is carefully considered during cutting to maximize the desired color display.
Zircon is the hardest and most durable of the three, with a Mohs hardness ranging from 6.5 to 7.5. However, it is also known for being somewhat brittle, meaning it can chip or cleave if struck with significant force. Its most remarkable gemological property is its exceptionally high refractive index (1.92–1.98) and strong dispersion (0.039), which is higher than diamond's. This gives a well-cut zircon a brilliant sparkle and fiery flashes of color, making it an excellent and affordable alternative to diamond in jewelry.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, December’s birthstones are rich in symbolism, with each stone carrying specific meanings that have evolved over time.
Turquoise is universally recognized as a stone of protection and healing. Across many cultures, it was believed to ward off negative energy and physical harm. The Apache tribes thought turquoise could be found by following a rainbow to its end, linking it to celestial guidance and good fortune. In modern crystal healing, turquoise is associated with emotional balance, stress relief, and fostering friendship and loyalty. Its connection to the throat chakra makes it a popular stone for those seeking to improve communication and self-expression.
Tanzanite, as a relatively new gem, has quickly developed a modern symbolism centered on transformation and spiritual awakening. Its unique color, which seems to bridge the physical and spiritual realms (blue and violet), makes it a powerful stone for meditation and intuition. It is often said to encourage a higher consciousness and to help its wearer navigate significant life changes with grace and insight. Its association with new beginnings makes it a meaningful gift for those embarking on a new chapter in life.
Zircon is traditionally linked to wisdom, prosperity, and honor. In the Middle Ages, it was believed to bring restful sleep and ward off evil spirits and nightmares. It is also considered a stone of clarity, helping to focus the mind and enhance learning. Its brilliant sparkle is seen as a reflection of inner clarity and truth. In some traditions, zircon is associated with attracting wealth and good fortune, making it a popular talisman for business and personal success.
Care and Cleaning: Preserving Your December Gem
Proper care is essential to maintain the beauty and longevity of these birthstones, and the methods vary significantly based on their individual properties.
Turquoise requires the most careful handling. Due to its softness and porosity, it should be protected from chemicals, including perfumes, lotions, and household cleaners. Clean turquoise jewelry only with a soft, dry cloth. Avoid ultrasonic cleaners and steam, as these can cause cracking or discoloration. Store turquoise pieces separately to prevent scratches from harder gems or metals.
Tanzanite is relatively delicate and should be handled with care. It is best cleaned with warm, soapy water and a soft brush, avoiding any harsh chemicals. While it is generally safe for occasional wear in rings, it is better suited for earrings, pendants, and brooches where it is less likely to receive impact. Protective settings, such as bezels, are recommended for tanzanite jewelry to guard against chipping.
Zircon, while harder, is brittle. It can be cleaned using warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe for untreated zircon, but caution is advised for stones that have been fracture-filled or coated. To prevent chipping, avoid wearing zircon in rings during heavy manual work or activities where the stone might be struck. Store zircon jewelry in a padded box to protect it from harder gems that could scratch it.
Conclusion
December’s birthstones—turquoise, tanzanite, and zircon—offer a captivating spectrum of blue, each with a distinct personality. Turquoise connects us to ancient traditions and the protective energies of the earth. Tanzanite dazzles with its modern elegance and transformative symbolism, a product of a unique geological moment. Zircon provides brilliant fire and durability, a gem of wisdom and clarity that has adorned humanity for centuries. Together, they provide a diverse and meaningful selection for those born in the final month of the year, ensuring that every December birthday can be celebrated with a gemstone that perfectly reflects their personal style and story.