For individuals born in the final month of the year, the birthstone selection is exceptionally generous. Unlike months with a single designated gem, December is represented by a "blue trio" of gemstones: tanzanite, turquoise, and zircon. These three distinct minerals share a predominantly cool color palette that evokes the frosty elegance of winter, yet each possesses a unique geological origin, a distinct history, and a specific set of gemological characteristics.
This comprehensive guide explores the science, history, and symbolism of December's three official birthstones. From the ancient protective amulets of turquoise to the modern rarity of tanzanite and the diamond-like brilliance of zircon, these gems offer a wide spectrum of choices for collectors, jewelry enthusiasts, and those seeking a personal connection to their birth month.
History and Lore of the Blue Trio
The history of December's birthstones spans millennia, encompassing ancient civilizations, modern discoveries, and a rich tapestry of cultural beliefs.
Turquoise: The Ancient Protector Turquoise is unequivocally the oldest and most traditional of the December birthstones. Prized for thousands of years across numerous cultures, its distinctive color has adorned everything from ancient Egyptian pharaohs' burial masks to Native American jewelry. The gemstone’s name derives from the French phrase pierre turquoise, meaning "Turkish stone," reflecting its historic trade route through Turkey to Europe. Historically, it was believed to possess protective powers, serving as a talisman against harm and misfortune. Its enduring popularity as a birthstone is rooted in this deep history of use as a symbol of safety and spiritual grounding.
Tanzanite: The Modern Marvel In stark contrast to turquoise’s ancient lineage, tanzanite is a very recent addition to the gemological world. Discovered in 1967 in Tanzania, this violet-blue variety of the mineral zoisite quickly captured the attention of the jewelry industry. Its name honors its exclusive geographic origin. The gemstone’s rise to prominence was meteoric, culminating in its official designation as a December birthstone. Its association with transformation and spiritual awareness is a modern interpretation, fitting for a gemstone that represents a new era in gem mining.
Zircon: The Sparkling Stone Zircon, often confused with the synthetic cubic zirconia, is a natural gemstone with exceptional brilliance and fire. While it occurs in a variety of colors, the blue variety is the specific birthstone for December. Historically, zircon has been valued for its diamond-like appearance, offering an affordable alternative with remarkable sparkle. It has long been associated with wisdom, balance, and prosperity. The confusion with cubic zirconia has sometimes overshadowed its natural beauty, but for those in the know, blue zircon remains a prized and dazzling selection.
Geological Formation and Sources
Understanding how these gems are formed and where they are mined provides insight into their rarity and value.
Turquoise Formation and Sources Turquoise is an opaque mineral that forms near the surface of the earth through a process of percolation. Acidic, copper-rich water seeps through rock containing aluminum and phosphorus minerals. Over long periods, this process creates veins and nodules of turquoise. The presence of other minerals, such as iron or chromium, can alter the color, leading to greenish hues or dark, spiderweb-like inclusions known as "matrix."
The sources of turquoise are as varied as its colors. Historically, Persian turquoise from Iran’s ancient mines has been the most prized variety, celebrated for its vivid, evenly saturated sky-blue color and characteristically minimal to nonexistent matrix. This premium turquoise is admired for its purity and remarkable hue. In the United States, the Sleeping Beauty Mine in Arizona was a significant source of highly valued turquoise known for its pure, robin’s-egg blue color and exceptionally low matrix, though its mining operations have been a point of variation in availability.
Tanzanite Formation and Sources Tanzanite’s geological story is unique. It forms through a process of heating and hydration of the mineral zoisite. This metamorphic event occurred millions of years ago in the Merelani Hills of northern Tanzania, near the majestic Mount Kilimanjaro. The specific conditions required for its formation are incredibly rare, leading to the gemstone’s status as "a million-times rarer than diamond." The source area is geographically limited to a small mining zone, making tanzanite one of the most scarce gemstones in the world. This exclusivity adds to its allure and market value.
Zircon Formation and Sources Zircon is a mineral belonging to the group of nesosilicates. It is one of the oldest minerals on Earth, with crystals found in ancient crustal rocks. It forms during the crystallization of magma and is found in both igneous and metamorphic rocks. While zircon is mined in various locations globally, including Australia, Sri Lanka, and Thailand, the specific blue variety often results from heat treatment of brownish zircon crystals. The gem's durability and resistance to weathering have allowed ancient zircon crystals to survive through eons, making them a testament to the earth's geological history.
Gemological Properties
Each of the December birthstones has a distinct profile of physical and optical properties, which dictate their durability, appearance, and care requirements.
| Gemstone | Mineral Family | Hardness (Mohs) | Chemical Composition | Key Optical Feature |
|---|---|---|---|---|
| Turquoise | Phosphate | 5 - 6 | CuAl₆(PO₄)₄(OH)₈·4H₂O | Opaque, often with matrix |
| Tanzanite | Zoisite | 6 - 7 | Ca₂Al₃(SiO₄)₃(OH) | Trichroism (blue, purple, burgundy) |
| Zircon | Nesosilicate | 6.5 - 7.5 | ZrSiO₄ | High refractive index, high dispersion |
Turquoise With a hardness on the Mohs scale of 5 to 6, turquoise is relatively soft compared to other jewelry gemstones. It is also porous, which means it can be susceptible to damage from chemicals, oils, and even the natural oils from human skin. Its opacity is a defining characteristic; the most valued specimens exhibit a uniform, vibrant color without excessive matrix. The chemical formula includes water, making it sensitive to heat and dry environments.
Tanzanite Tanzanite ranks between 6 and 7 on the Mohs scale, making it more durable than turquoise but softer than quartz. Its most remarkable gemological property is trichroism. When viewed from different angles, the stone can display three distinct colors: blue, purple, and a reddish-burgundy. Gem cutters orient the rough crystal to display the dominant blue-violet hue. The vast majority of tanzanite on the market has been heat-treated to remove the brownish-yellow hues present in the rough, resulting in the saturated blue and violet colors consumers desire.
Zircon Zircon is the hardest of the three December stones, with a Mohs hardness of 6.5 to 7.5, making it quite durable for jewelry. It possesses a very high refractive index (1.92-1.98), which is higher than that of a diamond, giving it exceptional brilliance. It also has high dispersion (0.039), the property responsible for the "fire" or flashes of spectral color seen in a well-cut stone. Blue zircon, in particular, displays stunning brilliance and fire, often rivaling diamonds. However, zircon can be brittle due to its crystal structure, requiring careful handling to avoid chipping.
Symbolism and Metaphysical Beliefs
Across cultures and through history, gemstones have been imbued with symbolic meaning and metaphysical properties. The December birthstones are no exception.
- Turquoise is widely regarded as a stone of protection, healing, and good fortune. It is believed to shield the wearer from negative energy and harm. Many cultures associate it with calming influences, communication, and the balancing of chakras. Its color is often linked to tranquility and spiritual grounding.
- Tanzanite is a modern crystal associated with spiritual awareness, transformation, and intuition. As a relatively new discovery, its metaphysical lore is less ancient, but it is often linked to the "Third Eye" chakra, enhancing perception and higher consciousness. It is said to promote a sense of calm and purpose.
- Zircon is known as a stone of wisdom, balance, and prosperity. It is believed to help with self-esteem and to open the way to spiritual and material wealth. The blue variety is particularly associated with peace and tranquility, aiding in restful sleep and calming anxieties.
Care and Cleaning
Proper maintenance is essential to preserve the beauty and integrity of these gemstones. Their varying hardness and chemical compositions require specific care protocols.
Turquoise Care Due to its porosity and relatively low hardness, turquoise requires gentle handling. It should be cleaned with only a soft, dry cloth. Avoid all chemicals, including household cleaners, perfumes, and lotions, as they can cause discoloration or damage. Prolonged exposure to direct sunlight or heat can also fade the color. It is best to store turquoise jewelry separately to prevent scratching by harder stones.
Tanzanite Care While harder than turquoise, tanzanite should still be handled with care. It can scratch easily and is susceptible to chipping due to its cleavage properties. The safest method for cleaning is warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam cleaning, as the heat and vibrations can cause fractures. It is advisable to remove tanzanite jewelry before engaging in physical activities.
Zircon Care Zircon is relatively durable but can be brittle. It is generally safe to clean with warm, soapy water and a soft brush. However, caution is needed with sudden temperature changes, as extreme thermal shock can cause zircon to crack. While it is hard enough for everyday wear in rings, it is best set in protective settings like bezels to prevent impact damage to its edges.
Conclusion
December's birthstones offer a remarkable diversity within a cohesive color theme. The trio of tanzanite, turquoise, and zircon provides a gem for every preference: the traditional and protective turquoise, the rare and transformative tanzanite, and the brilliant and wise zircon. Each stone carries a unique combination of geological rarity, historical significance, and symbolic meaning. For the December-born individual, the choice is not merely aesthetic but an opportunity to connect with a gemstone that resonates on a personal level, whether through its ancient lore, its modern allure, or its dazzling physical properties.