December is a unique month in the gemological calendar, offering not one, but three recognized birthstones: Turquoise, Tanzanite, and Zircon. This trio provides a remarkable spectrum of color, history, and meaning for those born under the sign of Capricorn, particularly individuals born in the latter half of the month. While turquoise has been associated with December for centuries, tanzanite and zircon are more modern additions, reflecting evolving traditions and the discovery of new gemstone sources. This article delves into the distinct geological origins, gemological properties, historical significance, and cultural symbolism of these three stones, providing a detailed resource for gemstone enthusiasts, jewelry buyers, and students of gemology.
The connection between these stones and the Capricorn zodiac sign is a key theme. Capricorns, born between December 22 and January 19, are often characterized by their ambition, discipline, and practical nature. The birthstones of December are said to complement these traits, offering grounding, clarity, and focus. From the ancient protective qualities of turquoise to the vibrant rarity of tanzanite and the enduring brilliance of zircon, each stone carries a unique narrative that enriches our understanding of this multifaceted month.
History and Lore
The historical tapestry of December's birthstones is rich and varied, with turquoise holding the most ancient claim to the title. Turquoise has been revered for millennia by numerous civilizations. In ancient Egypt, it was considered a sacred stone, closely associated with the goddess Hathor, who embodied love and protection. Egyptians adorned themselves with turquoise, believing it brought good fortune and warded off harm. Its significance extended to other ancient cultures, including the Persians and Native Americans, who also held the stone in high esteem for its protective and spiritual qualities.
In contrast, tanzanite and zircon are relative newcomers to the birthstone canon. Tanzanite's history is remarkably brief, tracing its origins to a single, geographically confined event. It was discovered in Tanzania in 1967, a find that would soon captivate the gem world with its stunning violet-blue hues. Its rapid ascent to popularity and eventual inclusion on modern birthstone lists underscores the dynamic nature of gemological traditions. Zircon, while known for a much longer period, experienced a resurgence in recognition as a December birthstone in more recent times, particularly the blue variety, which is now celebrated for its brilliance and symbolism.
The assignment of these stones to the Capricorn zodiac sign is a more modern interpretation, linking gemstone properties to astrological personality traits. For those born on December 23rd, the symbolism is said to extend beyond the general December birthstones to encompass traits associated with the first decan of Capricorn. Individuals born on this date are described as practical, old-fashioned, and embodying the resourceful nature of the Capricorn sea-goat symbol. The stones are believed to enhance Capricorn's inherent strengths—such as discipline, ambition, and resilience—while providing balance to challenges like stubbornness or a tendency toward aloofness.
Geological Formation and Sources
The geological origins of these three birthstones are as distinct as their appearances, a testament to the diverse processes that create gemstones.
Turquoise is a hydrated phosphate of copper and aluminum. It forms in arid regions through a secondary process involving the weathering of copper-rich rocks. Groundwater carrying dissolved minerals percolates through these rocks, depositing turquoise in veins or nodules. Significant sources of turquoise include the United States, particularly in Arizona, New Mexico, and Nevada, which are famous for their distinctive matrix patterns. Other major sources are Iran and China, each producing turquoise with unique color characteristics and matrix formations.
Tanzanite is a blue-violet variety of the mineral zoisite. Its formation requires a unique and rare combination of geological conditions, making it an exceptionally limited gemstone. Tanzanite is found exclusively in the Merelani Hills of northern Tanzania, a small mining area near the base of Mount Kilimanjaro. The specific geological event that created tanzanite is believed to have occurred only once in the Earth's history, which explains why it is found in only one location globally. This rarity contributes significantly to its value and desirability.
Zircon is a zirconium silicate (ZrSiO₄) and is one of the oldest minerals on Earth, with some crystals dating back billions of years. It forms in a variety of geological settings, including igneous, metamorphic, and sedimentary rocks. Major sources of zircon include Cambodia, Sri Lanka, Myanmar, and Australia. The gemstone is often found in placer deposits, having weathered from its original host rock and been transported by water. While zircon is available in a range of colors, the blue variety is particularly sought after for December birthstones.
Gemological Properties
Understanding the physical and chemical properties of these stones is essential for proper identification, care, and appreciation. The following table summarizes key gemological data for Turquoise, Tanzanite, and Zircon.
| Property | Turquoise | Tanzanite | Zircon |
|---|---|---|---|
| Mineral Species | Hydrated phosphate of copper and aluminum | Blue-violet variety of zoisite | Zirconium silicate |
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | Ca₂Al₃(SiO₄)₃(OH) | ZrSiO₄ |
| Crystal System | Triclinic | Orthorhombic | Tetragonal |
| Hardness (Mohs Scale) | 5 - 6 | 6.5 - 7 | 6.5 - 7.5 |
| Refractive Index | 1.61 - 1.65 | 1.69 - 1.70 | 1.92 - 2.01 |
| Specific Gravity | 2.6 - 2.9 | 3.35 | 4.6 - 4.7 |
| Luster | Waxy to dull | Vitreous to adamantine | Adamantine |
| Key Identification | Often porous, can be dyed or stabilized | Distinctive violet-blue color, pleochroism | High refractive index, strong fire (dispersion) |
Turquoise is a relatively soft stone (Mohs 5-6) and is often porous, which makes it susceptible to damage and discoloration. It is commonly treated with wax or resin to improve its stability and luster. Its color ranges from sky blue to greenish blue, often influenced by the presence of iron or other trace elements.
Tanzanite is known for its trichroism—the ability to show three different colors (typically blue, violet, and burgundy) when viewed from different angles under light. This property is a key identifier for the gem. With a hardness of 6.5 to 7, it is suitable for jewelry but requires care to avoid sharp blows. The most valuable tanzanite exhibits a deep, saturated violet-blue hue.
Zircon is renowned for its exceptional brilliance and fire, which rival that of diamond. Its high refractive index and strong dispersion make it one of the most sparkly gemstones. Blue zircon, which is typically heat-treated from brown zircon, is the variety most associated with December. Zircon has a hardness of 6.5 to 7.5, making it durable enough for most jewelry settings, though it can be brittle due to its crystal structure.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these stones are imbued with a wealth of symbolic meaning and metaphysical beliefs, which have been attributed to them across various cultures and eras.
Turquoise has long been a symbol of protection, wisdom, and good fortune. In many traditions, it is believed to ward off negative energy and bring peace to the wearer. Its soothing blue color is associated with tranquility and emotional balance. For Capricorns, turquoise is said to offer grounding energy and mental clarity, helping to stabilize the throat chakra and enhance communication. It is also thought to promote problem-solving skills and encourage a more open-minded perspective.
Tanzanite, a stone of transformation, is linked to intuition, insight, and spiritual awakening. Its discovery in the 20th century has led to its association with modernity and progress. Metaphysically, it is believed to facilitate a connection between the heart and mind, promoting emotional depth and compassion. For Capricorns, tanzanite is said to enhance their ambition while providing clarity of thought, helping to transform goals into tangible achievements. It is also considered a stone of good fortune and prosperity.
Zircon is traditionally associated with energy, focus, and protection. Blue zircon, in particular, is thought to enhance mental focus and promote restful sleep. It is believed to cleanse the aura and protect against negative influences. For Capricorns, zircon is said to strengthen their innate discipline and resilience, offering support in maintaining stability and achieving long-term goals. Its brilliant sparkle is also linked to attracting prosperity and good luck.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, given their distinct physical properties.
Turquoise requires gentle handling due to its relative softness and porosity. It should be cleaned with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals, as these can damage the stone or strip away any stabilizing treatments. It is best to remove turquoise jewelry before engaging in activities that could cause impact or exposure to cosmetics, perfumes, or lotions.
Tanzanite should be cleaned with warm, soapy water and a soft brush. While it is relatively hard, it can be prone to chipping or cracking if subjected to sharp blows. It is advisable to store tanzanite jewelry separately to avoid scratches from harder stones. Ultrasonic cleaners are not recommended, as the vibrations can cause internal fractures to worsen.
Zircon is durable but can be brittle. Cleaning can be done with warm, soapy water and a soft brush. Avoid sudden temperature changes and harsh chemicals. While zircon is generally stable, some blue zircon may be treated with heat, and prolonged exposure to strong light or heat could potentially alter its color. It is best to store zircon jewelry in a soft cloth to prevent scratching, as it is harder than many other gems but can be scratched by diamond or corundum.
Conclusion
The trio of December birthstones—Turquoise, Tanzanite, and Zircon—offers a fascinating journey through geology, history, and symbolism. From the ancient protective talisman of turquoise to the recently unearthed brilliance of tanzanite and the timeless sparkle of zircon, each stone provides a unique connection to the month of December and the Capricorn zodiac sign. Their distinct origins, from the arid copper-rich regions of the American Southwest to the singular deposit in Tanzania and the ancient crustal formations of the world, highlight the incredible diversity of our planet's gemological resources. For those born in December, these stones are more than mere adornments; they are carriers of legacy, meaning, and personal significance, embodying the strength, ambition, and enduring appeal of the Capricorn spirit.