The month of December is uniquely distinguished in the world of gemology by its trio of official birthstones: Turquoise, Tanzanite, and Zircon. This selection offers those born in the final month of the year a remarkable spectrum of blue, from the tranquil sky blue of ancient Turquoise to the vivid violet-blue of Tanzanite and the brilliant fire of Zircon. Unlike most months, which are typically associated with a single gem, December's multiple birthstones reflect a modern evolution of tradition, providing a variety of colors, histories, and properties to suit individual tastes. These gems are not merely beautiful adornments; they are carriers of deep historical lore, fascinating geological origins, and distinct gemological characteristics that captivate collectors, jewelers, and enthusiasts alike. This article provides a detailed exploration of each of these three principal December birthstones, delving into their histories, geological formation, physical properties, and the symbolism that has secured their place as cherished tokens for those born under the winter sky.
History and Lore of December's Gems
The historical journey of December's birthstones is as varied as the gems themselves, with each stone carrying a legacy steeped in ancient culture and tradition.
Turquoise, arguably the most ancient of the trio, has been a prized gemstone for millennia. Its name offers a clue to its long and winding path into global consciousness. The word "Turquoise" is derived from the French phrase pierre turquoise, meaning "stone of Turkey." This nomenclature arose because the gem was first brought to Europe from Turkish bazaars by traders. Its origins, however, lie much further east. Revered by a multitude of ancient civilizations, Turquoise was a significant cultural artifact for the Egyptians, Persians, Native Americans, and Tibetans. Ancient Egyptians adorned themselves with Turquoise jewelry, believing it offered protection and good fortune. Similarly, Persian and Tibetan cultures integrated the stone into ritual and ceremonial objects, valuing its purported protective qualities, especially during travel. This ancient belief in its power to safeguard the wearer has cemented Turquoise's status as a stone of protection and good fortune through the ages.
Tanzanite is a far more recent addition to the world of precious gems, making its appearance on the scene in the late 20th century. Unlike the ancient lineage of Turquoise, Tanzanite's history is short but dramatic. It was first discovered in the Merelani Hills of northern Tanzania in 1967. The gem's discovery was relatively modern, and its identity was almost immediately intertwined with the global jewelry giant Tiffany & Co., which recognized its stunning beauty and unique color. The company introduced Tanzanite to the world in 1968, naming it after its country of origin and promoting it heavily. Its rarity and captivating violet-blue hue quickly made it a favorite in contemporary jewelry design. While it lacks the ancient lore of Turquoise, its symbolism is often linked to modern concepts of transformation and new beginnings, a reflection of its recent and singular geological birth.
Zircon, often confused with the synthetic cubic zirconia, is one of the oldest minerals on Earth, with zircon crystals found in Australia dating back over 4.4 billion years. While the blue variety is the focus for December, Zircon comes in a wide range of colors. The blue hue is most often achieved through heat treatment of brownish zircon. Historically, Zircon was a protective amulet, believed to encourage prosperity and honor. Its brilliant sparkle and fire have made it a popular diamond simulant for centuries. The inclusion of blue Zircon into the official birthstone list occurred in 1952, when the Jewelry Industry Council of America updated the list originally standardized in 1912 by the National Association of Jewelers. This addition provided December-born individuals with a high-clarity, sparkling blue option.
The modern list of birthstones was formalized in 1912, with subsequent updates reflecting new discoveries and market trends. The 1952 update added Zircon, and in 2002, the American Gem Trade Association and the Jewelry Industry Council of America added Tanzanite, officially recognizing it as a third December birthstone. This evolution highlights how birthstone lists are not static but adapt to include new and significant gemstones.
Geological Formation and Sources
The origins of these gems are as diverse as their histories, spanning different geological processes and mining locations across the globe.
Turquoise is not formed from magma like many other gemstones but is a secondary mineral deposited by water. It is a hydrated phosphate of copper and aluminum. The process begins with water rich in copper and other minerals seeping into the bedrock. Over vast periods, this water reacts with existing aluminum-rich rocks, causing the precipitation of the minerals that form Turquoise. The presence of copper is responsible for the stone's characteristic blue color, while iron can shift the hue towards green. The distinctive brown or black veining, known as the "matrix," is actually fragments of the host rock (such as limonite or sandstone) that become trapped within the Turquoise during its formation. Major sources for Turquoise include Iran (historically the source of the finest "Persian Turquoise"), the Southwestern United States (Arizona, New Mexico, Nevada), Tibet, and Chile.
Tanzanite is remarkable for its extreme geological rarity. It is a variety of the mineral zoisite and is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. The gem's formation is a result of a unique geological event. Approximately 585 million years ago, a massive tectonic plate shift and mountain-building event occurred. This event subjected the rocks to intense heat and pressure, causing the metamorphism of the existing minerals into the blue zoisite we know as Tanzanite. The specific and limited geological conditions required for its creation make it thousands of times rarer than diamond. Mining is conducted in four small, distinct blocks in the Merelani area, and the finite nature of this single-source location is a primary driver of its value.
Zircon is a nesosilicate mineral that forms in the magma of igneous rocks, such as granite and syenite. As the magma cools, zircon crystals are among the first to crystallize. It is also found in metamorphic rocks and as a detrital mineral in sedimentary deposits (placer deposits). Zircon is known for its exceptional durability and resistance to heat, which makes it a reliable indicator mineral for dating the age of rocks. Today, the primary sources for gem-quality Zircon include Thailand, Cambodia, Sri Lanka, and Australia. Australia is home to some of the oldest zircon crystals on the planet.
Blue Topaz is also frequently mentioned as a December birthstone, particularly as an alternative or modern option. It is found in various locations worldwide, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States. The United States, specifically Texas, has designated Blue Topaz as its official state gem.
Gemological Properties: A Comparative Analysis
Understanding the physical and chemical properties of these gems is crucial for both jewelers and consumers, as these characteristics determine their durability, care requirements, and overall value.
Turquoise is an opaque gem with a hardness of 5 to 6 on the Mohs scale, making it relatively soft and susceptible to scratches and chemicals. Its chemical composition is a hydrated phosphate of copper and aluminum. Its specific gravity ranges from 2.60 to 2.90. The stone's color can range from sky blue to bluish-green to apple green, with the most prized color being an even, intense "robin's egg" blue. The presence of the matrix, the host rock veins, is a key identifying feature and is often incorporated into the stone's aesthetic.
Tanzanite is the pleochroic variety of the mineral zoisite, meaning it displays different colors when viewed from different crystal directions. Typically, it shows blue, violet, and burgundy hues. It has a hardness of 6.5 to 7 on the Mohs scale, making it more durable than Turquoise but still requiring careful handling to avoid chipping or breaking due to its cleavage properties. Its chemical composition is calcium aluminum hydroxyl silicate. The most valuable color is the deep, saturated "violet-blue" that is often enhanced by heat treatment, which removes the brownish tones naturally present in the rough stone.
Zircon is one of the hardest of the December gems, with a hardness of 7.5 on the Mohs scale, though it is brittle due to its perfect cleavage in two directions. Its brilliance and fire are exceptional, often exceeding that of a diamond. Its chemical composition is zirconium silicate. For the December birthstone, the desirable color is a vivid, clear blue, which is typically produced by heating brown zircon crystals. Zircon has a high refractive index (1.92-1.98) and strong birefringence, which gives it a distinctive double refraction effect.
Blue Topaz, when included in the list of December gems, is a silicate mineral with a hardness of 8 on the Mohs scale, making it the most durable of the group for everyday wear. It is a transparent gemstone with a high degree of brilliance. Most of the blue topaz on the market has been irradiated and heat-treated to achieve its deep blue color from its naturally pale state.
The following table summarizes the key properties of the three official December birthstones:
| Property | Turquoise | Tanzanite | Zircon (Blue) |
|---|---|---|---|
| Mineral Family | Phosphate | Zoisite (Amphibole) | Nesosilicate |
| Chemical Formula | Hydrated phosphate of copper & aluminum | Calcium aluminum hydroxyl silicate | Zirconium silicate |
| Hardness (Mohs) | 5 - 6 | 6.5 - 7 | 7.5 (Brittle) |
| Crystal System | Triclinic | Orthorhombic | Tetragonal |
| Transparency | Opaque | Transparent to Translucent | Transparent |
| Primary Color(s) | Blue, bluish-green, green | Blue, violet, burgundy (pleochroic) | Blue (from heat-treated brown) |
| Sources | Iran, USA, Tibet, Chile | Tanzania (only source) | Thailand, Cambodia, Sri Lanka, Australia |
Symbolism and Metaphysical Beliefs
Across cultures and centuries, gemstones have been attributed with symbolic meanings and metaphysical powers. Each of December's birthstones carries a unique set of beliefs.
As noted, Turquoise is predominantly a stone of protection, good fortune, and healing. Its historical use as a travel amulet persists in modern lore, where it is believed to safeguard the wearer from accidents and bring calm to turbulent situations. It is also associated with wisdom, tranquility, and balance, often used in spiritual practices to align the chakras and promote emotional stability.
Tanzanite, being a modern gem, has developed a more contemporary set of symbolic meanings. It is widely associated with transformation, new beginnings, and intuition. Its dramatic discovery in the 20th century and its striking color shift lend themselves to interpretations of spiritual awakening and higher consciousness. It is often linked to the throat and crown chakras, believed to facilitate clear communication and a deeper connection to one's inner wisdom.
Zircon is traditionally linked to honor, prosperity, and wisdom. In the Middle Ages, it was worn as a protective amulet against plague and lightning. Today, it is believed to aid in sleep, promote spiritual growth, and boost self-esteem. Its brilliant sparkle is said to inspire clarity of thought and purpose.
While these metaphysical beliefs are popular in many circles, they fall outside the realm of established gemological science and are considered cultural lore rather than verifiable properties.
Care and Cleaning
The diverse physical properties of December's birthstones necessitate different approaches to their care and maintenance.
Turquoise requires the most care due to its porosity and relative softness. It is sensitive to heat, chemicals, and even prolonged exposure to skin oils and cosmetics, which can cause discoloration. Cleaning should be done gently with warm, soapy water and a soft cloth. Ultrasonic and steam cleaners are strictly forbidden. It is best to store Turquoise jewelry separately to avoid scratches.
Tanzanite is also delicate and requires careful handling. While it is harder than Turquoise, its cleavage properties make it susceptible to chipping if struck against a hard surface. It is not recommended for rings that will be worn daily, such as engagement rings, but is suitable for pendants and earrings. Cleaning with warm, soapy water and a soft brush is safe. Like Turquoise, it should not be cleaned with ultrasonic or steam cleaners.
Zircon, despite its higher hardness, is brittle and has perfect cleavage, making it vulnerable to hard blows. It should be protected from rough wear. Cleaning with warm, soapy water is recommended. While some sources may suggest caution with ultrasonic cleaners due to its cleavage, a gentle ultrasonic cleaning is often considered safe for Zircon unless it has surface-reaching fractures. However, steam cleaning is not advised.
Conclusion
December is exceptionally fortunate to claim three distinct and magnificent birthstones: the ancient and protective Turquoise, the rare and transformative Tanzanite, and the brilliant and wise Zircon. Each gem offers a unique narrative, from Turquoise's journey through ancient Persian and Egyptian civilizations to Tanzanite's singular and dramatic birth in the hills of Tanzania, and Zircon's billion-year-old legacy embedded in the Earth's crust. Their shared spectrum of blue connects them visually, yet their individual gemological properties, histories, and symbolic meanings provide a rich tapestry of choice for those born in the month. Whether one is drawn to the opaque, rustic charm of Turquoise, the pleochroic fire of Tanzanite, or the diamond-like brilliance of Zircon, each stone serves as a meaningful and beautiful link to the natural world and the enduring human tradition of finding significance in the earth's most precious creations.