December is a month of celebration, marking the end of the year and the beginning of winter. For those born in this final month, the birthstone selection is uniquely abundant, offering a palette of cool, wintry blues that mirror the season's icy skies and deep twilight. Unlike most months, which typically have one or two birthstones, December is traditionally associated with multiple gems, providing a wide array of choices for personal preference and style. The most widely recognized modern birthstones for December are turquoise, zircon, blue topaz, and tanzanite. Each of these gemstones carries its own distinct history, geological origin, and set of characteristics, from the ancient, opaque charm of turquoise to the brilliant, fiery sparkle of zircon. This article delves into the rich tapestry of these four gems, exploring their historical significance, geological formation, gemological properties, and the cultural beliefs that have surrounded them for centuries. Whether you are a gemstone enthusiast, a jewelry buyer, or a student of gemology, understanding the unique qualities of each of December's birthstones will help you appreciate their enduring beauty and value.
History and Lore: From Ancient Amulets to Modern Marvels
The history of December's birthstones spans millennia, with some gems being among the oldest known to humanity, while others are products of modern discovery. The selection of birthstones for the month is not based on a single, immutable list but has evolved over time, reflecting changes in availability, cultural trends, and official recognition by organizations like the American Gem Society (AGS) and the National Association of Jewelers (NAJ).
Turquoise stands as the most ancient of the group. Its name derives from the French pierre turquoise, meaning "Turkish stone," as it was brought to Europe through gem markets in Constantinople, Turkey, from its primary sources in Persia and the Sinai Peninsula. This gem was a favorite amulet from the earliest times, prized by indigenous cultures, ancient Egyptians, Incas, and Mayas. Its relative softness made it easy to cut into various shapes and inscribe with protective symbols. A powerful symbol of protection, it was believed to ward off evil spirits and danger, and to bring good fortune. In Tibetan culture, turquoise was considered a birthstone for fortune, health, and success, and was even used as currency. For lovers and married couples, it was a cherished gem believed to preserve relationships and friendship when given as a gift. A fascinating folk belief held that turquoise could warn its wearer of approaching illness or danger by becoming pale, acting as a personal health monitor.
Zircon is one of the oldest minerals on Earth, with deposits found that are over 4.4 billion years old. For centuries, it was confused with other blue gems, notably diamond and blue topaz, due to its exceptional brilliance and fire. In the Middle Ages, zircon was believed to promote honor, wisdom, and prosperity, and to protect travelers from injury and illness. It was also said to induce sleep and ward off evil spirits. While it has a long history, its formal recognition as a December birthstone is a more modern development, emerging as a popular alternative to the traditional turquoise.
Tanzanite is the youngest of the four, a true gem of the modern era. It was not discovered until 1967 in the Merelani Hills of Tanzania, near Mount Kilimanjaro. Its discovery was dramatic; a mass of blue-violet crystals was found by a Masai herdsman, and its unique color and clarity quickly captured the gemological world's attention. Initially mistaken for sapphire, it was later identified as a variety of the mineral zoisite. Tiffany & Co. recognized its potential and launched a major marketing campaign in 1968, giving it the name "tanzanite" after its country of origin. Its rapid rise to prominence led to its official adoption as a December birthstone in 2002 by the American Gem Society, making it one of the most recent additions to the birthstone calendar. Its lore is tied to themes of transformation, new beginnings, and spiritual awakening.
Blue Topaz completes the quartet. While topaz itself is an ancient gem, its use as a blue birthstone for December is a more recent commercial development. Natural blue topaz is rare; most of the vibrant blue topaz seen in jewelry today is the result of irradiation and heat treatment of colorless topaz. Its crisp, icy blue color perfectly complements the wintry theme of December. It was added to the list of December birthstones later than the others, offering a durable and affordable option for those seeking a classic blue gem. Its symbolism is often linked to clarity, communication, and calm.
Geological Formation and Sources
The origins of these gems are as diverse as their histories, formed under vastly different geological conditions and mined from specific locations across the globe.
Turquoise is a secondary mineral formed in arid regions where acidic, copper-rich groundwater percolates through rocks containing aluminum and phosphorus. This process can take millions of years. The finest-quality turquoise often comes from Iran (Persia), known for its uniform, sky-blue color without matrix (the host rock). The Sinai Peninsula was another historic source. In the United States, the Southwest region—particularly Arizona, Nevada, and New Mexico—is famous for its turquoise, which often features a distinctive matrix (web of host rock). The most prized American turquoise is from the Sleeping Beauty mine in Arizona, known for its pure, solid sky blue color.
Zircon is a zirconium silicate that forms in the cooling of magma, particularly in granites and pegmatites. It is a durable mineral that can survive geological upheaval. Significant sources include Cambodia, Sri Lanka, Thailand, and Australia. Australian zircon is known for its brownish hues, which can be heat-treated to produce blue or colorless gems. The blue variety of zircon, which is the most popular for December, is almost always heat-treated to remove brownish tones. This heat treatment is stable and is a standard industry practice.
Tanzanite is found in only one location in the world: the Merelani Hills of northern Tanzania, a small area of just a few square kilometers. Its formation is linked to the unique geological conditions of the East African Rift, where high temperatures and pressures transformed zoisite into tanzanite. This extreme rarity of source contributes significantly to its value and allure. The mining is concentrated in three blocks (A, B, and C), with Block C being the most famous for producing the highest-quality gemstones.
Blue Topaz is a silicate mineral that forms in igneous rocks, particularly in pegmatites and high-temperature veins. Its primary sources include Brazil, Mexico, and the United States (notably Texas and Utah). As mentioned, most blue topaz on the market is colorless topaz that has been treated with irradiation and heat to achieve its blue color. This treatment is permanent and safe, and the resulting gem is stable for jewelry use. The most famous variety of blue topaz is the Swiss Blue, known for its intense, electric blue hue.
Gemological Properties
Understanding the physical and optical properties of these gems is crucial for both identification and care. The following table summarizes key gemological characteristics based on the information available from the provided sources.
| Gemstone | Mineral Family | Chemical Formula | Mohs Hardness | Typical Treatments | Notable Properties |
|---|---|---|---|---|---|
| Turquoise | Phosphate | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | Stabilization (impregnation with resin) | Opaque, often porous, can be dyed or stabilized. Color ranges from sky blue to greenish blue. |
| Zircon | Silicate (Zirconium) | ZrSiO₄ | 6.5 - 7.5 | Heat treatment (to produce blue/colorless) | High refractive index, high dispersion ("fire"). Blue zircon is typically heat-treated from brownish colors. |
| Blue Topaz | Silicate (Aluminum) | Al₂SiO₄(F,OH)₂ | 8 | Irradiation and heat treatment (to produce blue) | Typically transparent, can be faceted to show brilliance. Color is usually even and saturated. |
| Tanzanite | Silicate (Zoisite) | Ca₂Al₃(SiO₄)₃(OH) | 6.5 - 7 | Heat treatment (to enhance blue color) | Pleochroic (shows different colors from different angles: blue, violet, burgundy). |
Turquoise is relatively soft and porous, making it susceptible to damage from chemicals, heat, and prolonged exposure to sunlight, which can cause fading. It is often stabilized with a clear resin or wax to improve its durability and color retention. Its opaque nature means it is often cut into cabochons rather than faceted gems.
Zircon is one of the hardest gemstones on this list, with a Mohs hardness of 6.5 to 7.5, making it reasonably durable for jewelry. Its most defining characteristic is its high refractive index and high dispersion, which gives it exceptional brilliance and fire, rivaling that of diamond. Blue zircon is almost always heat-treated; the natural blue color is extremely rare.
Blue Topaz is very hard (Mohs 8), making it highly resistant to scratching and suitable for all types of jewelry, including rings. Its transparency and even color make it ideal for faceted cuts. The blue color is a result of post-mining treatment, which is permanent and stable.
Tanzanite has a Mohs hardness of 6.5 to 7, which is moderate. It is more fragile than topaz or zircon and can be prone to chipping if knocked hard, requiring protective settings for rings. Its most notable gemological property is its strong pleochroism; a rough tanzanite crystal may show red, yellow, green, and blue hues, but the heat treatment used to enhance its blue color also stabilizes the pleochroic effect, typically resulting in a dominant blue-violet hue from the table and a burgundy tone from other angles.
Symbolism and Metaphysical Beliefs
The symbolic meanings attributed to December's birthstones are as varied as the gems themselves, often rooted in ancient traditions and modern interpretations.
Turquoise is universally recognized as a stone of protection, healing, and good fortune. It is considered a grounding stone that brings peace to the wearer and is thought to absorb negative energies. In many cultures, it is a symbol of friendship and love, often given as a gift to protect relationships. Its association with the sky and water connects it to themes of tranquility and emotional balance.
Zircon is often associated with wisdom, clarity, and prosperity. It is believed to stimulate the mind and enhance focus, making it a stone for scholars and those seeking intellectual growth. In some traditions, it is said to promote a sense of dignity and honor. Its brilliant sparkle is thought to mirror a clear and enlightened mind.
Tanzanite, a gem of modern discovery, carries symbolism related to transformation and new beginnings. Its unique blue-violet color is linked to spiritual awareness, intuition, and the opening of higher consciousness. It is often called the "stone of magic" or the "stone of transformation," believed to aid in navigating life changes with clarity and grace. Its rarity adds to its symbolism of uniqueness and individuality.
Blue Topaz is associated with communication, clarity of thought, and calm. It is believed to help articulate thoughts and feelings, making it a stone for public speakers and communicators. Its cool blue color is linked to tranquility, reducing stress and promoting a sense of peace and relaxation.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these gemstones, and their care requirements differ based on their physical properties.
Turquoise requires the most careful handling. It is porous and sensitive to chemicals, including cosmetics, lotions, and even perspiration. It should be wiped with a soft, dry cloth after wear. Avoid soaking it in water or using ultrasonic cleaners, as this can damage the stone, especially if it has been stabilized. Store it separately to avoid scratches from harder gems.
Zircon is relatively durable but can be brittle due to its crystal structure. It is best cleaned with warm water, mild soap, and a soft brush. Avoid sudden temperature changes, as this can cause fracture. It is generally safe for ultrasonic cleaning, but caution is advised for older or heavily included stones.
Blue Topaz, being very hard, is easy to care for. It can be cleaned with warm soapy water and a soft brush. It is safe for ultrasonic cleaning. However, avoid exposing it to extreme heat, as this could alter its color (though the treated blue color is generally stable).
Tanzanite is the most delicate of the four in terms of toughness. It should be cleaned only with warm soapy water and a soft brush. It is not recommended for ultrasonic or steam cleaning, as the vibrations and heat can cause fractures. Due to its moderate hardness and perfect cleavage in one direction, it should be protected from hard blows and stored carefully, preferably in a soft pouch.
Conclusion
December's birthstones—turquoise, zircon, blue topaz, and tanzanite—offer a remarkable diversity of color, history, and character, all united by their cool, wintry blue hues. From the ancient, protective talisman of turquoise to the brilliant fire of heat-treated zircon, the crisp, durable blue of treated topaz, and the transformative, pleochroic beauty of tanzanite, each gem provides a unique option for those born in the final month of the year. Their varied origins, from the arid deserts of Iran and the American Southwest to the volcanic pegmatites of Brazil and the singular hills of Tanzania, tell stories of Earth's geological wonders. Understanding their gemological properties and care requirements ensures that these stones can be cherished for generations. Ultimately, the abundance of choice for December allows individuals to select a birthstone that not only captures the essence of the season but also resonates with personal style and symbolic meaning, making it a truly special gift for any December birthday.