The month of December is uniquely distinguished in the world of gemology by offering not one, but three official birthstones, each celebrated for its distinct shade of blue. While many months have evolved their birthstone lists over time, December’s trio—Turquoise, Tanzanite, and Zircon—provides a remarkable spectrum of color, history, and geological origin. This abundance of choice allows those born in the final month of the year to select a gem that resonates with personal style, from the ancient, opaque robin's egg blue of Turquoise to the fiery, brilliant clarity of Blue Zircon. Historically, Turquoise has stood as the traditional emblem for December, but modern standards have embraced the vibrant Tanzanite and the diamond-like Zircon to complete the palette.
The significance of these stones extends beyond mere aesthetics; they are deeply intertwined with cultural lore, metaphysical beliefs, and specific geological conditions that make them rare and valuable. Turquoise, one of the oldest known gemstones, has adorned everything from ancient pharaohs to Victorian jewelry, prized for its distinctive color and matrix patterns. Tanzanite, a relative newcomer discovered in the 20th century, offers a pleochroic display of violet-blue that captivated the jewelry world almost immediately. Blue Zircon, often confused with synthetic cubic zirconia, is actually a natural gemstone with a high refractive index that rivals the sparkle of a diamond. Together, they represent a geological and historical journey that spans millennia and continents. This article will explore the history, formation, gemological properties, and symbolism of these three magnificent birthstones, providing a comprehensive guide for enthusiasts, collectors, and those born in December.
History and Lore of the Azure Gems
The historical narrative of December's birthstones is anchored primarily by Turquoise, which boasts a lineage stretching back thousands of years. The very name of the stone reveals its ancient trade routes; "Turquoise" is derived from the French expression pierre torques, meaning "Turkish stone." This nomenclature arose because the gem was imported to Europe from Turkish bazaars during the 13th century. However, the stone's origins lay further east. Ancient Persia (modern-day Iran) was the primary source for the highly prized sky blue turquoise, a color so specific that it is still commonly referred to as "Persian blue." Beyond the Middle East, the Sinai Peninsula in Egypt served as a major supplier of turquoise stones in antiquity, with mines that operated for millennia. The United States is currently the world's largest provider of turquoise, contributing significantly to the modern market.
Turquoise has enjoyed a continuous presence in jewelry and ornamentation throughout history. It was immensely popular in Victorian jewelry, a period during which the color blue was highly fashionable. The stone’s allure was not limited to Europe; it holds deep cultural significance for Native American tribes in the Southwest United States, where it has been used in ceremonial jewelry and art for centuries. Culturally, Turquoise is viewed as a stone that changes color with age, a characteristic that has led to associations with optimism and the ability to "embrace the light."
In stark contrast to the ancient history of Turquoise, Tanzanite is a gemstone of the modern era. It was not mined until the 1960s, making it one of the youngest gemstones to enter the commercial market. Despite its youth, it quickly rose to prominence due to its singular color and rarity. Blue Zircon also has a long history, though it is often overshadowed by the confusion regarding its name. Natural zircon is one of the oldest minerals on Earth, but its use as a gemstone has fluctuated in popularity. In the Victorian era, colorless zircon was a popular diamond simulant, valued for its brilliance. Today, the blue variety is the specific birthstone for December, offering a compelling alternative to the diamond with its own unique fire.
Geological Formation and Sources
Understanding the origins of these gemstones reveals a fascinating divergence in how they are created and where they are found. Turquoise is an opaque mineral that forms in arid regions where acidic, copper-rich groundwater percolates through pre-existing rocks. Over geological time, this water reacts with minerals containing aluminum and phosphorus, depositing turquoise in the cracks and crevices of the bedrock. The presence of copper dictates the blue color, while iron often shifts the hue toward green. The dark lines and shapes frequently seen in turquoise cabochons are actually fragments of the surrounding host rock, known as "matrix," which become part of the polished gem.
Tanzanite is the trade name for the mineral zoisite and is found in only one location on the planet: the Merelani Hills of Northern Tanzania. This extreme geographic limitation makes the stone exceptionally rare. It is believed to have been formed by a unique combination of intense heat and pressure during the formation of the East African Rift Valley. The heat "metamorphosed" the host rock, changing the zoisite's chemical structure and creating the signature violet-blue hue. While the stone is naturally blue, most tanzanite found in jewelry has been heat-treated to enhance and stabilize the color, a standard practice in the gem trade.
Zircon is a mineral belonging to the nesosilicates group and is distinct from synthetic cubic zirconia (CZ). It is a common mineral found in many parts of the world, including Australia, Thailand, and Cambodia. However, the gem-quality blue zircon used in jewelry is typically the result of heat treatment. Colorless or pale brown zircon is heated to high temperatures to remove the brownish tones and induce a brilliant blue color. This process mimics the natural geological conditions that some zircon experiences, resulting in a gemstone with exceptional brilliance and fire.
Gemological Properties
The physical and optical properties of December's birthstones vary significantly, which influences their use in jewelry and their care requirements. The following table summarizes the key gemological data for each stone based on the available information.
| Gemstone | Chemical Composition | Hardness (Mohs Scale) | Crystal System | Transparency | Distinctive Features |
|---|---|---|---|---|---|
| Turquoise | Hydrated phosphate of copper and aluminum | 5 - 6 | Triclinic | Opaque | Often contains "matrix" (host rock); color ranges from powdered blue to greenish robin's egg blue. |
| Tanzanite | Calcium aluminum hydroxyl sorosilicate | 6.5 - 7 | Orthorhombic | Transparent | Strong pleochroism (displays violet, blue, and burgundy colors); rich violet-blue hue. |
| Zircon | Zirconium silicate | 6.5 - 7.5 | Tetragonal | Transparent | High refractive index (approaching diamond); brilliant sparkle; often heat-treated to achieve blue color. |
Turquoise is the softest of the three, with a hardness ranging from 5 to 6 on the Mohs scale. Its opacity means it is almost always cut as a cabochon (a polished dome) rather than faceted. The stone's color is its defining characteristic, ranging from "powdered blue" to a "greenish robin egg blue." The presence of the dark matrix creates unique patterns in every stone, ensuring that no two pieces of turquoise jewelry are exactly alike.
Tanzanite is harder, rating between 6.5 and 7 on the Mohs scale, making it suitable for rings and pendants, though it requires protection from sharp blows due to its cleavage properties. Its most famous gemological characteristic is pleochroism—the ability to show different colors when viewed from different crystal directions. A cut tanzanite may display vivid blue, violet, and sometimes reddish-burgundy tones depending on the orientation. The most desirable color is a deep, rich violet-blue.
Zircon is the hardest of the trio, with a rating of 6.5 to 7.5. It is also the most brilliant, possessing a high refractive index that gives it exceptional fire and sparkle, often compared to that of a diamond. This brilliance makes it a popular choice for faceted gemstones. Blue zircon typically appears as a bright, clear blue, distinct from the softer tones of turquoise or the violet hues of tanzanite.
Symbolism and Metaphysical Beliefs
Across cultures and centuries, these gemstones have been attributed with various powers and meanings, ranging from protection to spiritual transformation. These beliefs add a layer of depth to the stones, making them popular choices for jewelry intended as gifts.
Turquoise is widely regarded as a stone of protection, good fortune, and spiritual grounding. Historically, it was believed to ward off evil and protect the wearer from injury. In many cultures, it is a symbol of success, happiness, and prosperity. The belief that Turquoise changes color to warn its owner of impending danger or illness is a long-standing piece of lore, reinforcing its status as a guardian stone. It is also associated with rational thinking and emotional balance, making it a favored stone for those seeking stability.
Tanzanite, being a modern discovery, has developed a new set of symbolic associations relatively quickly. It is often linked to transformation, new beginnings, and spiritual awakening. Its unique tri-colored nature (pleochroism) is sometimes interpreted as representing the unification of the mind, body, and spirit. As a stone of the "new age," it is believed to facilitate higher consciousness and intuition, appealing to those undergoing significant life changes.
Zircon is associated with clarity, wisdom, and honor. It is believed to promote spiritual growth and help the wearer connect with their higher self. In some traditions, Zircon is thought to aid in sleep when placed under a pillow, warding off nightmares and promoting restful rest. Its brilliant sparkle is often seen as a metaphor for mental clarity and the ability to see the truth in situations. For those born in December, Zircon is said to bring prosperity and honor to its wearer.
Care and Cleaning
Due to their differing physical properties, the care required for each of December's birthstones varies significantly. Proper maintenance is essential to preserve the beauty and integrity of the gem.
Turquoise is relatively porous and sensitive to chemicals. It should be protected from cosmetics, perfumes, and harsh detergents, which can discolor the stone or damage its polish. Cleaning should be done gently with warm, soapy water and a soft cloth. Ultrasonic cleaners and steam cleaners are strictly forbidden as they can cause cracking or color loss. Given its lower hardness, Turquoise jewelry should be stored separately to avoid scratches from harder gems.
Tanzanite is more durable than Turquoise but is still considered somewhat fragile due to its cleavage. It is susceptible to breaking if struck against a hard surface. While it can be cleaned with warm, soapy water and a soft brush, it should never be subjected to ultrasonic cleaners, which can cause internal fractures to expand. Sudden temperature changes should also be avoided.
Zircon is the most durable of the three but is brittle. It can fracture if hit hard, so it requires careful handling, especially in rings that are exposed to daily wear. Cleaning with warm, soapy water is safe. However, some heat-treated zircon may be susceptible to ultrasonic cleaners if the stone has existing fractures. It is generally safer to use a soft brush and mild soap. Because of its brilliance, Zircon tends to show fingerprints and smudges easily, so frequent gentle cleaning is recommended to maintain its sparkle.
Conclusion
December's birthstones offer an unparalleled variety for those born in the month, encompassing a range of colors from the soft, earthy greens of Turquoise to the vivid, shifting blues of Tanzanite and the brilliant, diamond-like sparkle of Blue Zircon. While Turquoise remains the traditional and most historically significant stone, the inclusion of Tanzanite and Zircon reflects the evolving nature of gemology and consumer preference. Each stone carries a distinct narrative: Turquoise connects us to ancient civilizations and the natural landscapes of the American Southwest; Tanzanite represents the rarity of a single geographic location and the dynamism of modern discovery; and Zircon offers a glimpse into the deep geological time of our planet, rivaling the diamond in its optical beauty. Together, they provide a rich palette for jewelry design and a wealth of symbolism for those who wear them. Understanding their unique histories, properties, and care requirements allows collectors and jewelry buyers to make informed choices that celebrate the enduring allure of these azure gems.