December is unique in the calendar of birthstones. While most months are assigned a single gem, December is celebrated with a veritable treasure chest of blue-hued stones. The primary traditional birthstones are turquoise, zircon, and tanzanite, with blue topaz frequently cited as a modern addition. This abundance reflects the month's wintry aesthetic—a palette of icy skies, deep twilight, and cool, serene depths. Each stone carries its own distinct history, geological origin, and set of characteristics, offering a wide spectrum of choices for those born in the final month of the year. This article delves into the geology, properties, lore, and care of these four remarkable December birthstones, providing a comprehensive resource for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore: From Ancient Protections to Modern Discoveries
The concept of birthstones has deep historical roots, often traced back to the biblical description of Aaron's breastplate, which featured twelve gemstones representing the tribes of Israel. This tradition evolved over centuries, with various cultures and time periods associating specific stones with months. For December, the stones selected carry narratives that span from ancient civilizations to modern geological discoveries.
Turquoise stands as the oldest and most storied of the December gems. Evidence suggests it has been cherished for over 5,000 years, with its use documented in ancient Egypt, Mesopotamia, and the Americas. In Egypt, it was used for intricate jewelry and amulets, while in the Americas, it was revered by Native American tribes such as the Navajo, Zuni, and Pueblo. Its name is derived from the French pierre turquoise, meaning "Turkish stone," as it was initially transported to Europe through Turkish traders from the Persian mines. Historically, turquoise was believed to be a protective stone, warding off falls and negative energy. It was also associated with wisdom, tranquility, and friendship, and was often worn by royalty, including the famed Egyptian Pharaoh Tutankhamun, whose burial mask was adorned with turquoise.
In contrast, tanzanite is a product of the modern era. Discovered in the Merelani Hills of northern Tanzania in 1967, it is one of the youngest gemstones to achieve widespread recognition. Its discovery is attributed to a Maasai herdsman who noticed blue crystals in the region, which were later identified as a new variety of the mineral zoisite. The gem was quickly marketed by Tiffany & Co., who named it after its country of origin and promoted its unique violet-blue color. Its lore is thus inherently modern, often linked to themes of transformation, new beginnings, and heightened intuition, reflecting its recent and dramatic entrance into the gemstone world.
Zircon has a history that predates modern gemology, though it is often confused with the synthetic cubic zirconia. Natural zircon is one of the oldest minerals on Earth, with crystals found in Australia dating back over 4.4 billion years. For centuries, it has been used as a gemstone, valued for its brilliance and fire. In the Middle Ages, it was believed to promote honor, purity, and wisdom, and to bring restful sleep. It was also used as a talisman for travelers. While it is available in a range of colors, the blue variety is particularly prized for December, and its association with clarity and mental acuity has persisted through history.
Blue topaz, while not a traditional birthstone for December in older lists, has become a popular modern alternative. Its history as a gemstone is ancient, with the name "topaz" believed to originate from the Sanskrit word tapas, meaning "fire," or the Greek topazos. However, natural blue topaz is rare; the vast majority of blue topaz on the market today is colorless topaz that has been irradiated and heat-treated to achieve its blue hues. This technological process made blue topaz widely available and affordable, leading to its inclusion in many contemporary birthstone lists. Its symbolism is often tied to clarity, communication, and calmness, aligning with its serene color.
Geological Formation and Sources
The formation and geographic origins of these stones are as diverse as their histories. Each requires specific geological conditions, which in turn dictate their availability and character.
Turquoise is a secondary mineral that forms in arid regions where acidic, copper-rich groundwater percolates through rocks containing aluminum and phosphorus. This process occurs over millions of years, filling cavities and fractures with the turquoise mineral. Key sources include: * Iran (Persia): Historically the most prized source, producing the classic "robin's egg blue" turquoise with little to no matrix. * Southwestern United States: Nevada, Arizona, and New Mexico are major producers, often yielding turquoise with a distinctive matrix (the host rock inclusions). The "Sleeping Beauty" mine in Arizona is famous for its pure, sky-blue stone without matrix. * China: A significant modern source, producing a wide range of qualities. * Other locations: Egypt, Tibet, India, Mexico, and parts of Central Asia and Africa also contribute to the global supply.
Tanzanite is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This single-source origin makes it exceptionally rare. It forms through a complex geological process involving the metamorphism of limestone, with the presence of vanadium (which gives it its blue color) and the specific heat and pressure conditions unique to this small area. The mining is concentrated in four small blocks, making the stone's future supply a subject of discussion among gemologists.
Zircon is a common mineral found in igneous, metamorphic, and sedimentary rocks worldwide. Major gem-quality sources include: * Cambodia: Known for producing high-quality blue and brown zircons. * Sri Lanka: A traditional source for a variety of colors. * Myanmar (Burma): Produces some of the finest zircons. * Australia: Home to the oldest zircon crystals on Earth. * Norway, Nigeria, and Brazil are also notable producers. The blue color in natural zircon is typically achieved through heat treatment of brown or reddish-brown crystals.
Blue Topaz is primarily sourced from Brazil, but also comes from Nigeria, Sri Lanka, Mexico, and the United States (particularly Texas). As noted, the intense blue hues of commercial blue topaz are almost always the result of laboratory treatment, a fact that is important for buyers to understand. Natural light blue topaz (often called "sky blue") is rare and more valuable.
Gemological Properties: A Scientific Comparison
Understanding the physical and chemical properties of these gems is crucial for identifying them, assessing their quality, and determining their suitability for jewelry. The table below summarizes key gemological data for the four December birthstones, based on standard gemological references.
| Property | Turquoise | Zircon | Tanzanite | Blue Topaz |
|---|---|---|---|---|
| Mineral Species | Hydrated copper aluminum phosphate | Zircon (ZrSiO₄) | Zoisite (Ca₂Al₃(SiO₄)₃(OH)) | Topaz (Al₂SiO₄(F,OH)₂) |
| Crystal System | Triclinic | Tetragonal | Orthorhombic | Orthorhombic |
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O | ZrSiO₄ | Ca₂Al₃(SiO₄)₃(OH) | Al₂SiO₄(F,OH)₂ |
| Mohs Hardness | 5 – 6 | 6.5 – 7.5 | 6.5 – 7 | 8 |
| Refractive Index | 1.610 – 1.650 | 1.92 – 2.01 | 1.691 – 1.700 | 1.609 – 1.627 |
| Specific Gravity | 2.60 – 2.90 | 4.60 – 4.70 | 3.35 | 3.49 – 3.57 |
| Toughness | Poor to Fair | Good | Fair | Very Good |
| Common Treatments | Stabilization (wax/resin impregnation), dyeing | Heat treatment (to achieve blue), irradiation | Heat treatment (to remove brown/yellow hues) | Irradiation and heat treatment (to achieve blue) |
| Typical Inclusions | Matrix (host rock), spiderweb patterns, pitting | Crystals, fluid inclusions, zoning | Finger-like inclusions, needles, color zoning | Liquid inclusions, fingerprint inclusions |
Turquoise is relatively soft and porous, which is why most commercial turquoise is stabilized—impregnated with wax, resin, or plastic to enhance durability, color, and luster. Natural, untreated turquoise is rare and valuable. Its matrix, the web-like pattern of the host rock, is a key identifier and can be a desirable feature, as seen in many American Southwestern varieties.
Zircon is the oldest of the minerals and has a high refractive index and strong dispersion (fire), often compared to diamond. It is generally durable, though it can be brittle due to its tetragonal crystal structure and may cleave if struck. The bright "electric" blue of zircon is typically the result of heat treatment, which is stable and widely accepted in the trade.
Tanzanite is known for its strong trichroism, displaying three different colors (blue, violet, and burgundy-red) when viewed from different crystal directions. This property is responsible for its captivating color shifts. It is moderately hard but has fair toughness, meaning it is more susceptible to chipping or breaking from a sharp blow compared to a diamond or sapphire. Most tanzanite is heat-treated to remove brownish-yellow hues, a process that is permanent and considered standard.
Blue Topaz is the hardest of the four December stones (8 on the Mohs scale), making it very suitable for everyday wear. Its hardness and affordability have made it a popular choice for modern jewelry. As mentioned, the vivid blue colors (London Blue, Swiss Blue) are almost exclusively created through irradiation and heat treatment, a process that is safe and does not affect the stone's stability.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each December birthstone carries a legacy of symbolic meaning and metaphysical belief, often tied to its color and history.
- Turquoise is universally associated with protection, good fortune, and healing. It is considered a grounding stone that promotes inner calm, wisdom, and friendship. In many cultures, it is believed to absorb negative energy and protect the wearer from harm, both physical and spiritual. Its connection to the sky and water makes it a symbol of tranquility and clarity.
- Zircon is linked to mental clarity, wisdom, and honor. It is thought to enhance focus, stimulate the mind, and promote a sense of balance and stability. Historically, it was believed to bring prosperity and protect against evil spirits. The blue variety, in particular, is associated with peace and calm.
- Tanzanite, as a modern stone, is imbued with meanings of transformation, intuition, and new beginnings. Its unique color and recent discovery associate it with spiritual awakening, higher consciousness, and the ability to see beyond the mundane. It is often called the "stone of vision."
- Blue Topaz symbolizes calm, clarity, and communication. Its soothing blue color is believed to reduce stress and anxiety, while its clarity is thought to aid in honest expression and truthful communication. It is also associated with love and affection in some traditions.
Care and Cleaning: Preserving Your Gemstone's Beauty
Proper care is essential to maintain the beauty and longevity of any gemstone, and the requirements vary significantly among the December birthstones due to their differing physical properties.
Turquoise requires the most careful handling. With a hardness of only 5-6 and a porous nature, it is susceptible to scratches, chemicals, and temperature changes. It should be cleaned with a soft, damp cloth and mild soap. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals (including perfumes, lotions, and household cleaners). Stabilized turquoise is more durable but should still be treated with care. Store it separately from harder gems to prevent scratching.
Zircon is relatively durable but can be brittle. It is generally safe to clean with warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as vibrations could cause internal fractures to worsen. Sudden temperature changes should also be avoided.
Tanzanite has moderate hardness but fair toughness. It is best cleaned with warm, soapy water and a soft brush. Avoid ultrasonic and steam cleaners, which can cause damage due to its inclusions and cleavage. It is also sensitive to heat, so keep it away from high temperatures.
Blue Topaz, with its hardness of 8, is the most durable of the group and can withstand more rigorous cleaning. It is safe to use warm, soapy water, a soft brush, and even an ultrasonic cleaner (though caution is advised for stones with significant inclusions). However, it is still wise to avoid sudden temperature shocks and harsh chemicals.
For all gemstones, it is advisable to remove jewelry before engaging in physical activities, household chores, or swimming to prevent impacts and exposure to damaging substances.
Conclusion
December offers a remarkable selection of birthstones, each with a distinct identity. Turquoise provides ancient protection and a classic, earthy beauty. Zircon offers brilliant fire and mental clarity, with a history spanning billions of years. Tanzanite captures the imagination with its modern discovery, rare single-source origin, and captivating color play. Blue Topaz delivers accessible, durable, and serene blue tones for contemporary jewelry. Together, they form a blue treasury that reflects the cool, serene, and profound essence of the winter month. Whether chosen for its historical significance, geological wonder, symbolic meaning, or simply its stunning color, any of these stones makes a meaningful and beautiful birthstone for those born in December.