The final month of the year is unique in the world of gemology, offering not one, but three official birthstones for those born in December: Turquoise, Zircon, and Tanzanite. This trio represents a fascinating blend of ancient history, geological wonder, and modern discovery. While each stone possesses a distinct identity, they collectively share a palette of captivating blues and purples that echo the wintry skies of the December landscape. This article provides a comprehensive exploration of these celebrated gemstones, delving into their rich histories, gemological properties, and their esteemed place in both fine jewelry and cultural lore.
History and Lore
The story of December's birthstones is one of evolution, reflecting changes in trade, discovery, and tradition. The most ancient of these is Turquoise, a stone that has been cherished for millennia. Its name is derived from the French phrase pierre turquoise, meaning "Turkish stone," a reference to the gem's introduction to Europe through the Turkish trade routes. Long before its journey west, however, Turquoise was a sacred stone for ancient civilizations in the Americas. The Aztecs, and many other indigenous cultures of the region, incorporated the gem into intricate ceremonial objects, masks, and jewelry. Its significance was deeply rooted in spiritual beliefs, often associated with protection and connection to the heavens.
For much of modern history, Turquoise was the sole birthstone assigned to December. This was formalized in 1912 by the National Association of Jewelers (NAJ) in the United States, which established a standardized list of birthstones that has been largely influential ever since. However, the list was not static. The gemological community recognized the need to reflect both market availability and consumer desire for variety.
In 1952, the list was updated to include Zircon as a second December option. While its name might evoke images of the synthetic cubic zirconia, natural Zircon is one of the oldest minerals on Earth, with crystals dating back billions of years. For centuries, the brilliant, fire-filled blue varieties of Zircon were highly prized, often mistaken for sapphires by royalty and common folk alike. Its inclusion as a birthstone acknowledged its long-standing history as a significant gemstone in its own right.
The most recent addition came in 2002, when Tanzanite was added as an official birthstone for December, a decision ratified by the American Gem Trade Association (AGTA). This was a remarkable recognition for a gemstone that had only been discovered a few decades earlier, in the 1960s. Its rapid ascent to birthstone status speaks to its immense popularity and unique beauty. In 2016, the Jewelers of America further updated the list to include Tanzanite as an alternative to Zircon, solidifying its place alongside Turquoise and Zircon as the three official birthstones for the month.
Geological Formation and Sources
The three December stones originate from vastly different geological environments and are sourced from distinct regions of the globe, making their convergence as a birthstone group particularly interesting.
Turquoise is a secondary mineral that forms in arid or semi-arid regions through a unique geological process. It is a hydrated phosphate of copper and aluminum. Its formation occurs when acidic, copper-rich solutions seep through pre-existing aluminum-bearing rocks, such as feldspar, in the presence of water. Over millions of years, this process creates the dense, waxy nodules of Turquoise that are mined today. The finest quality Turquoise has historically come from the Nishapur region of Iran, which is known for its uniform, intense "robin's egg blue" color. In the United States, significant deposits are found in the Southwest, particularly in Arizona and Nevada, where the gem is a vital part of the region's mining heritage and cultural identity.
Zircon is a zirconium silicate and is a primary mineral found in igneous and metamorphic rocks. It is one of the oldest minerals known to exist, with some crystals found in Australia dating back over 4.4 billion years, making them the oldest pieces of Earth ever discovered. While Zircon occurs in a wide range of colors, the heat-treated brown zircon from Cambodia and Sri Lanka is the most common source for the vibrant blue stones seen in jewelry today. The heat treatment, which is a standard industry practice, enhances the color, transforming the naturally brown crystals into brilliant, sapphire-like blue gems. Other notable sources for Zircon include Thailand, Nigeria, and Tanzania.
Tanzanite is the youngest of the trio, both geologically and commercially. It is a variety of the mineral zoisite and owes its existence to a unique and highly specific geological event. Around 585 million years ago, a massive tectonic plate shift occurred in what is now the Merelani Hills of Northern Tanzania. This event subjected the zoisite crystals to intense heat and pressure, transforming them and infusing them with the elements (vanium and chromium) responsible for their signature violet-blue hue. This geological event occurred in only one place on Earth, making Tanzanite an exceptionally rare gemstone. Its origin is confined to a small, four-square-kilometer mining area near Mount Kilimanjaro, which underscores its scarcity and value.
Gemological Properties
While all three stones are celebrated for their beauty, they possess distinctly different physical and chemical properties, which influence their durability, appearance, and care requirements. The following table summarizes their key gemological characteristics based on established data.
| Property | Turquoise | Zircon | Tanzanite |
|---|---|---|---|
| Chemical Composition | Hydrated phosphate of copper and aluminum | Zirconium silicate (ZrSiO₄) | Calcium aluminum hydroxyl sorosilicate |
| Crystal System | Triclinic | Tetragonal | Orthorhombic |
| Hardness (Mohs Scale) | 5 - 6 | 6.5 - 7.5 | 6.5 - 7 |
| Refractive Index | 1.610 - 1.650 | 1.925 - 1.984 | 1.691 - 1.700 |
| Luster | Waxy to subvitreous | Adamantine (brilliant) | Vitreous (glass-like) |
| Color | Sky blue to bluish-green | Colorless, yellow, green, brown, blue | Blue, violet-blue, purplish |
Turquoise is the softest of the three stones (Mohs 5-6), making it more susceptible to scratching and damage. Its color is highly variable, ranging from the prized sky blue to greenish hues, often influenced by the presence of iron or zinc in its chemical makeup. The presence of a host rock matrix, visible as dark veins or webbing within the gem, is a common characteristic and can be a desirable feature in some designs.
Zircon is known for its exceptional brilliance and fire, which rivals that of diamond. This is due to its high refractive index, the highest among the three stones. With a hardness of 6.5 to 7.5, it is reasonably durable, though it can be brittle due to its crystal structure. The most sought-after color is the vivid blue, but it also appears in a variety of other shades.
Tanzanite displays a remarkable pleochroism, meaning it shows different colors when viewed from different crystal directions. A single stone can display blue, violet, and burgundy hues simultaneously. This phenomenon makes the cutting of Tanzanite a critical art to maximize its desired blue-violet color. With a hardness of 6.5 to 7, it is durable enough for most jewelry but requires more care than harder stones like sapphire or diamond.
Symbolism and Metaphysical Beliefs
Across cultures and through time, each of these stones has accumulated a rich tapestry of symbolic meaning and metaphysical beliefs.
Turquoise is perhaps the most storied of the three in this regard. For centuries, it has been regarded as a stone of protection, healing, and good fortune. Ancient Persian and Turkish warriors wore Turquoise amulets and adorned their horses and weapons with the gem, believing it would ward off injury and death. Many Native American cultures view Turquoise as a sacred stone that connects the physical and spiritual worlds, representing wisdom, tranquility, and good fortune. It is often called the "Master Healer" in metaphysical circles, believed to align all the chakras and provide a shield against negative energy.
Zircon has also been associated with protection and wisdom. In medieval Europe, it was believed to promote honor and purity in its wearer and to help with sleep. Blue Zircon, in particular, was a popular talisman for travelers, said to protect from injury and illness. It is also associated with prosperity, with some believing it can help its owner achieve their goals and attract wealth.
Tanzanite, as a newcomer, has quickly developed its own set of modern metaphysical meanings. It is often associated with transformation, intuition, and spiritual awakening. Believers claim that Tanzanite can open the throat and third-eye chakras, enhancing communication and psychic abilities. Its unique energy is said to help its wearer navigate change with confidence and to live a more authentic life. Because of its rarity, it is also seen as a stone of abundance and uniqueness.
Care and Cleaning
The different hardness levels and structural characteristics of the December birthstones necessitate specific care regimens to ensure their longevity.
Turquoise, being the softest, is highly porous and susceptible to damage from chemicals, heat, and even skin oils and lotions. It should be cleaned with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals like ammonia or acetone. To prevent discoloration, it is best to put Turquoise jewelry on after applying cosmetics and to remove it before swimming or showering.
Zircon is generally durable but can be brittle. It is best to clean it with warm water, a mild soap, and a soft brush. While it is not typically treated with heat or fracture-filling, it is wise to avoid sudden temperature changes, which could potentially cause fractures in older or included stones. Due to its brittleness, it should be protected from hard knocks.
Tanzanite requires careful handling due to its perfect cleavage in one direction, meaning it can be easily split or fractured if struck with force. It is also often heat-treated to achieve its stable blue color, but it is sensitive to extreme heat. Cleaning should be done with warm, soapy water and a soft brush. As with the other stones, ultrasonic and steam cleaners are not recommended. Given its relative softness and cleavage, it is best set in protective settings like bezels for rings worn daily.
Conclusion
The December birthstones—Turquoise, Zircon, and Tanzanite—offer a remarkable journey through geological time, human history, and cultural belief. From the ancient, protective amulets of Turquoise to the billion-year-old crystals of Zircon and the geologically miraculous discovery of Tanzanite, each gem provides a unique narrative. Together, they form a cohesive group defined by their captivating shades of blue and violet, making them a perfect representation of the winter month. For those born in December, the choice between these three stones is not merely a matter of color preference but an opportunity to connect with a legacy of rarity, beauty, and profound significance that has been cherished across ages and civilizations.