The month of December holds a unique distinction in the world of gemstones: it is the only month officially recognized with four distinct birthstones. This abundance of choice reflects the season's cool, wintry palette, mirroring the icy skies and deep twilight blues associated with its name. The traditional birthstones for December are Turquoise, Tanzanite, and Blue Zircon, with Blue Topaz frequently included as a modern, popular alternative. Each of these gemstones carries a rich history, distinct geological origins, and a unique set of gemological properties, offering a diverse selection to cater to individual preferences and personalities. This guide provides an in-depth exploration of these four December birthstones, drawing from historical, geological, and cultural sources to present a comprehensive overview for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore
The tradition of associating gemstones with specific months has ancient roots, believed to have originated in Mesopotamia and later adopted by the ancient Greeks and Romans. The December birthstones, in particular, have undergone several changes over time. Originally, only Turquoise and Zircon were considered December’s gemstones. However, in the 20th century, the list expanded to include Blue Topaz and Tanzanite. Tanzanite is the most recent addition, officially recognized in 2002. This expansion reflects the evolving nature of the birthstone tradition and the growing appreciation for new gemstone discoveries and their commercial appeal.
Turquoise is one of the oldest known birthstones, with a history spanning thousands of years. Its use can be traced back to ancient civilizations, including ancient Egypt, Greece, and Rome, where it was believed to possess mystical and healing properties. The name "Turquoise" itself is derived from the French term pierre turquoise, meaning "Turkish stone," as it was transported to Europe from Turkey. For centuries, it has been cherished for its distinctive color and has been a staple in jewelry and ceremonial objects across various cultures.
Zircon also has an ancient lineage. The name "Zircon" may come from the Persian word zargun, meaning "gold-colored," though Zircon is most famous for its colorless variety, which was often mistaken for diamond due to its high brilliance and fire. For centuries, Zircon was valued for its diamond-like appearance, and it was used in decorative arts and jewelry long before its identification as a distinct mineral.
Blue Topaz, while a popular modern choice, has a name with ancient origins. The name "Topaz" comes from the Greek word Topazios, which was the ancient name of an island in the Red Sea where the gemstone was said to be found. However, the stones from this island were later discovered to be Peridot, but the name stuck. Blue Topaz itself became widely available in the late 20th century, thanks to advancements in gemstone treatment that could produce its vivid, stable blue color.
Tanzanite is the newest of the four, discovered in the 1960s in Tanzania, East Africa. Its discovery was a significant event in the gemological world, and it was quickly embraced for its unique, pleochroic color that shifts between blue and violet. Due to its rarity and limited geographic source, it has been marketed as a gemstone for a new generation, often associated with transformation and new beginnings.
Geological Formation and Sources
The four December birthstones are formed through vastly different geological processes and are sourced from distinct regions around the world.
Turquoise is a hydrated phosphate of copper and aluminum. It forms in arid regions where acidic, copper-rich groundwater percolates through aluminum-bearing rocks, such as volcanic ash or sedimentary rocks, depositing turquoise in nodules or veins. Major sources of Turquoise include Iran (historically the most prized source), the southwestern United States (notably Arizona, New Mexico, and Nevada), China, and Egypt. The color of Turquoise, ranging from soft sky blue to greenish hues, is primarily determined by the presence of copper (blue) and iron (green). The matrix, or the host rock embedded in the gem, also contributes to its unique appearance.
Zircon is a zirconium silicate (ZrSiO₄) that forms in igneous and metamorphic rocks. It is one of the oldest minerals on Earth, with crystals found in rocks dating back billions of years. Zircon is mined in various locations, including Australia, which is the largest producer of gem-quality Zircon; Thailand, Cambodia, and Sri Lanka. The blue variety of Zircon, which is used as a December birthstone, is typically heat-treated to achieve its bright, clear blue color. Natural blue Zircon is rare, and most of the blue Zircon on the market has been treated to enhance its color.
Tanzanite is a variety of the mineral zoisite, specifically the blue-violet form. It is formed by the metamorphism of limestone rocks, a process that requires specific geological conditions found only in a small area of Tanzania, near the Merelani Hills. This limited geographic source makes Tanzanite significantly rarer than diamonds. The stones are mined from alluvial deposits, where they have been transported by water from their original host rock. The intense violet-blue color of Tanzanite is caused by trace amounts of vanadium, and it is often heat-treated to stabilize the color and remove brownish tones.
Blue Topaz is a variety of the mineral topaz, which is a fluorine-rich aluminum silicate. Topaz crystals form in igneous rocks, particularly in pegmatites and vapor-rich cavities in volcanic rocks. While Topaz occurs in many colors, natural blue Topaz is extremely rare. The vast majority of blue Topaz on the market is colorless Topaz that has been irradiated and heat-treated to produce a stable blue color. Major sources of Topaz include Brazil, Nigeria, Sri Lanka, and Mexico. The treatment process is standard industry practice and is accepted by gemological laboratories.
Gemological Properties
Understanding the physical and optical properties of these gemstones is crucial for both identification and care. The following table summarizes key gemological characteristics for each December birthstone based on the provided sources.
| Gemstone | Chemical Composition | Mohs Hardness | Crystal System | Key Optical Properties | Common Treatments |
|---|---|---|---|---|---|
| Turquoise | Hydrated copper aluminum phosphate | 5 - 6 | Triclinic | Opaque to translucent, waxy luster | Stabilization (impregnation with wax or resin), dyeing |
| Zircon | Zirconium silicate (ZrSiO₄) | 6.5 - 7.5 | Tetragonal | High refractive index, high dispersion ("fire") | Heat treatment for color (blue) |
| Tanzanite | Calcium aluminum silicate hydroxide | 6.5 - 7 | Orthorhombic | Strong pleochroism (blue/violet), vitreous luster | Heat treatment (to remove brownish tones) |
| Blue Topaz | Aluminum silicate fluoride hydroxide | 8 | Orthorhombic | Transparent, vitreous luster | Irradiation and heat treatment (for blue color) |
Hardness and Durability: - Topaz has the highest Mohs hardness of 8, making it very durable and resistant to scratching. It is an excellent choice for rings and daily-wear jewelry. - Zircon has a hardness ranging from 6.5 to 7.5, making it relatively durable but susceptible to chipping due to its brittleness. It is best suited for pieces that are less likely to receive hard impacts, such as earrings or pendants. - Tanzanite has a hardness of 6.5 to 7, but it has perfect cleavage in one direction, meaning it can split easily if struck with force. This makes it a delicate gemstone that requires careful handling and protective settings. - Turquoise is the softest of the four, with a hardness of 5 to 6. It is also porous and can be easily scratched or damaged. It is often stabilized (impregnated with wax or resin) to improve its durability and color consistency.
Color and Clarity: - Turquoise is prized for its opaque, waxy appearance. Its color ranges from soft sky blue to greenish blue, often with a characteristic matrix or webbing. - Zircon is typically bright and clear, with a high refractive index that gives it exceptional brilliance and fire. Blue Zircon is known for its vibrant, clear blue color. - Tanzanite is celebrated for its rich, violet-blue hue and strong pleochroism, displaying different shades of blue and violet depending on the viewing angle. - Blue Topaz displays a spectrum of blue shades, from pale, almost translucent "Sky Blue" to rich, vibrant "London Blue" and "Swiss Blue." It is typically transparent with few inclusions.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been imbued with symbolic meanings and metaphysical beliefs. While these are not scientifically verified, they remain an important part of the cultural legacy of these birthstones.
Turquoise is widely associated with protection, good fortune, and healing. Many cultures, including ancient Persians and Native American tribes, believed it could ward off evil and bring peace and balance. It is often seen as a steadying force, providing a sense of calm and grounding.
Zircon is linked to clarity, wisdom, and a sense of balance. It is believed to sharpen mental focus and promote spiritual growth. Historically, it was also thought to induce sleep and ward off evil spirits.
Tanzanite represents transformation, intuition, and new beginnings. Its recent discovery and unique color shift have led to modern associations with personal growth, spiritual awakening, and the ability to see the world from a new perspective.
Blue Topaz is associated with communication, truth, and calm. It is believed to help express thoughts and feelings clearly and to soothe stress and anxiety. Its cool blue color is often linked to tranquility and emotional balance.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone. The varying hardness and stability of the December birthstones require specific maintenance approaches.
Topaz and Zircon are relatively durable but can be brittle. They can be cleaned with warm water, mild soap, and a soft brush. Ultrasonic and steam cleaners are generally safe for Topaz but should be used with caution for Zircon, as it may be prone to fracturing if it has inclusions.
Tanzanite requires gentle care due to its perfect cleavage and moderate hardness. It is best cleaned with a soft brush, warm water, and mild soap. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals, as these can damage the stone or its setting.
Turquoise is the most delicate and porous of the four. It should never be cleaned with ultrasonic or steam cleaners, as these can cause cracking or discoloration. Clean it gently with a soft, dry cloth. Avoid exposure to chemicals, cosmetics, and prolonged sunlight, which can fade its color. It is advisable to store turquoise jewelry separately to prevent scratching.
Conclusion
December's four birthstones—Turquoise, Tanzanite, Blue Zircon, and Blue Topaz—offer a remarkable diversity in terms of history, geology, and appearance. From the ancient, earthy allure of Turquoise to the modern, transformative beauty of Tanzanite, each gemstone provides a unique connection to the season's cool elegance. Their distinct gemological properties, from the exceptional hardness of Topaz to the delicate cleavage of Tanzanite, inform both their use in jewelry and the care they require. Whether chosen for its symbolic meaning, its captivating color, or its personal significance, any of these four blue gems serves as a meaningful and cherished birthstone for those born in the twelfth month.