The month of December is uniquely represented by three distinct gemstones: turquoise, zircon, and tanzanite. This trio offers a remarkable spectrum of blue hues, from the sky-blue of turquoise to the fiery brilliance of zircon and the violet-blue of tanzanite. Each stone carries its own rich history, geological origin, and set of gemological properties, making the choice for a December birthstone a deeply personal one. This article explores the characteristics, origins, and significance of these three captivating gems, providing a comprehensive guide for enthusiasts, collectors, and anyone born in the final month of the year.
History and Lore
The history of December's birthstones is a tapestry woven from ancient traditions, modern additions, and evolving cultural preferences.
Turquoise boasts one of the longest histories as a gemstone. Evidence of its use dates back over 2,000 years in the Southwestern United States, where Native American cultures produced intricate beads, pendants, inlay work, and small sculptures from the stone. Its significance in Southwestern culture remains profound today. The gem's name is derived from the French pierre turquoise, meaning "Turkish stone," reflecting its historical trade route from Persia through Turkey. While its use is ancient, its formal recognition as a December birthstone is more recent. The modern standardization of birthstones in the United States began with the National Association of Jewelers (now Jewelers of America) in the early 20th century. Turquoise was later officially added to the December list, though historical charts also included lapis lazuli as a traditional alternative.
Zircon is the December birthstone with the longest continuous history of use as a gemstone. For centuries, it was the primary blue gemstone available and was often mistaken for sapphire due to its similar color and brilliance. Its high luster and fire, comparable to diamond, made it a prized gem in many cultures. Zircon is one of the oldest minerals on Earth, with deposits found that are billions of years old. It was a popular gem in Victorian England, where it was used in jewelry. In the modern birthstone chart, blue zircon is the designated stone for December, though it shares the month with other blue gems.
Tanzanite is the newest addition to the December birthstone family. This gemstone was only discovered in the late 20th century, making its history remarkably short but impactful. It was added to the official birthstone list in 2002 by the American Gem Trade Association (AGTA), marking the first change to the list in 50 years. Its rapid rise to prominence is a testament to its unique beauty and the effective marketing of its exclusive origin. While it lacks the ancient lore of turquoise and zircon, its symbolism is tied to themes of transformation and new beginnings, fitting for a stone that emerged so recently on the gemological scene.
The evolution of the birthstone chart itself is a key part of the story. The first official chart was established by the National Association of Jewelers in the United States, creating a standardized list. Over time, this chart has been updated to include alternative and modern options. For December, the list has expanded from traditional turquoise and lapis lazuli to include zircon, blue topaz, and tanzanite, reflecting both availability and consumer preference. Today, individuals often choose from this expanded list, selecting the stone that best appeals to their style and budget.
Geological Formation and Sources
The three December birthstones are formed through vastly different geological processes and are sourced from distinct regions of the world.
Turquoise is a hydrous phosphate of copper and aluminum, forming in arid regions where acidic, copper-rich groundwater interacts with minerals containing aluminum and phosphorus. This process occurs in the earth's crust, often in areas that were once volcanically active. The most significant sources of turquoise are found in the Southwestern United States (Arizona, Nevada, New Mexico), as well as in Iran, China, and Egypt. The stone's color, ranging from sky blue to greenish blue, is directly influenced by the presence of copper (blue) and iron (green). Bright blue turquoise is the most sought-after color. Unlike many gemstones, turquoise is typically opaque and is often cut into cabochon shapes, sometimes freeform to maximize the use of the rough material.
Zircon is a zirconium silicate (ZrSiO₄) and is one of the hardest minerals in nature, with a hardness of 7.5 on the Mohs scale. It forms in igneous and metamorphic rocks. The blue color in zircon is typically achieved through heat treatment of brownish zircon, a common practice in the gem trade. Natural blue zircon is rare. Major sources of zircon include Cambodia, Sri Lanka, and Thailand. The gem's high refractive index and strong dispersion (fire) give it exceptional brilliance, often compared to diamond. However, zircon can be brittle due to its perfect cleavage in two directions, making it susceptible to breakage if struck.
Tanzanite is a variety of the mineral zoisite, with the chemical formula Ca₂Al₃(SiO₄)₃(OH). It is found in only one location in the world: the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. This geographic exclusivity is a defining characteristic of tanzanite. The stone forms through a complex geological process involving the metamorphism of rocks and the presence of trace elements like vanadium, which give it its distinctive blue-violet color. The mining area is small, which contributes to the stone's rarity and value. Tanzanite is often heated to enhance its blue color, a stable treatment that is widely accepted in the trade.
The following table summarizes the key geological and sourcing information for the three gemstones based on the provided sources.
| Gemstone | Mineral Family | Chemical Formula | Key Sources | Primary Color Range |
|---|---|---|---|---|
| Turquoise | Phosphate | CuAl₆(PO₄)₄(OH)₈·4H₂O | Southwestern USA, Iran, China, Egypt | Sky blue to greenish blue |
| Zircon | Silicate | ZrSiO₄ | Cambodia, Sri Lanka, Thailand | Blue (often heat-treated), also brown, yellow, green |
| Tanzanite | Zoisite | Ca₂Al₃(SiO₄)₃(OH) | Merelani Hills, Tanzania | Blue to violet-blue |
Gemological Properties
Understanding the physical and chemical properties of these gemstones is crucial for their identification, care, and use in jewelry.
Turquoise is a phosphate mineral with a hardness ranging from 5 to 6 on the Mohs scale, making it relatively soft compared to other gemstones. It has a waxy to vitreous luster and is typically opaque, though some high-quality material can be translucent. Its specific gravity is around 2.6 to 2.8. Due to its porosity and softness, turquoise is susceptible to scratching and can be damaged by chemicals, perfumes, and even prolonged exposure to skin oils. It often contains a matrix (the host rock) or spiderweb veining, which is considered part of its character.
Zircon is a silicate mineral with a hardness of 7.5 on the Mohs scale, making it quite durable for jewelry, though its perfect cleavage makes it vulnerable to impact. It has a high refractive index (1.92-1.98) and very high dispersion (0.039), which gives it exceptional brilliance and fire. Zircon is pleochroic, meaning it can show different colors when viewed from different crystal directions. Heat treatment is commonly used to produce the desirable blue color from brown zircon, a process that is stable and widely accepted. Untreated zircon can be found in various colors, including brown, yellow, and green.
Tanzanite has a hardness of 6.5 to 7 on the Mohs scale, making it moderately durable but softer than sapphire or diamond. It has a vitreous luster and is typically transparent to translucent. A key characteristic of tanzanite is its strong trichroism, displaying three distinct colors: blue, violet, and reddish-brown when viewed from different angles. The stone is almost always heated to enhance its blue color and reduce the violet component, a treatment that is permanent and considered standard practice. Its specific gravity is 3.35, and its refractive index ranges from 1.691 to 1.700.
The hardness and durability of these stones directly impact their care. As noted in the sources, turquoise has a low hardness and is easily scratched. Zircon, despite its hardness, is prone to breakage due to its perfect cleavage. Tanzanite also has perfect cleavage and will break easily if struck. These properties necessitate careful handling and setting, often in protective jewelry designs like bezel settings, especially for rings.
Symbolism and Metaphysical Beliefs
Each of the December birthstones carries a legacy of symbolism and metaphysical beliefs, ranging from ancient lore to modern interpretations.
Turquoise has long been associated with protection, healing, and wisdom. In many cultures, it is considered a sacred stone that brings good fortune and health. Native American tribes believed it could ward off evil and protect the wearer from harm. It is also linked to communication and clarity of thought. In modern crystal healing, turquoise is said to promote inner calm, balance, and emotional stability. Its connection to the sky and water elements reinforces its symbolism of tranquility and protection.
Zircon is historically associated with wisdom, honor, and purity. It was believed to promote sleep, ward off evil spirits, and bring prosperity. In some traditions, it was thought to aid in spiritual growth and enhance one's connection to the divine. The blue variety, in particular, is linked to clarity of mind and clear communication. Its brilliance and fire have also made it a symbol of light and enlightenment.
Tanzanite, being a modern discovery, lacks ancient lore but has quickly developed its own set of symbolic meanings. It is often called the "stone of transformation" and is believed to facilitate a higher consciousness, intuition, and spiritual perception. Its unique violet-blue color is associated with the crown chakra, which governs spiritual connection and enlightenment. Some believe it can help overcome grief and loss, promoting a sense of peace and new beginnings. Its exclusivity to Tanzania adds a layer of symbolism related to uniqueness and destiny.
It is important to note that metaphysical beliefs are not scientifically verified and are considered by the gemological community as cultural or spiritual interpretations rather than factual properties. However, they remain a significant part of the allure and personal connection people have with these gemstones.
Care and Cleaning
Proper care is essential to maintain the beauty and integrity of these gemstones, given their distinct physical properties.
Turquoise requires gentle care due to its softness and porosity. It should be cleaned with only a soft, damp cloth and mild soap, avoiding any harsh chemicals or ultrasonic cleaners. It is best to remove turquoise jewelry before engaging in activities that could cause impact or exposure to chemicals, such as cleaning, swimming, or applying lotions. To prevent discoloration, it should be stored away from direct sunlight and heat, which can cause the stone to dry out and crack.
Zircon, while harder than turquoise, is brittle and has perfect cleavage. It should be protected from sharp blows and extreme temperature changes, which can cause it to fracture. Cleaning can be done with warm soapy water and a soft brush, but ultrasonic and steam cleaners are not recommended due to the risk of thermal shock. It is advisable to store zircon jewelry separately to avoid scratches from harder gemstones.
Tanzanite is also susceptible to cleavage and breakage. It should be handled with care and protected from impact. Cleaning can be performed with warm, soapy water and a soft brush, but ultrasonic and steam cleaners should be avoided. Due to its trichroism and the common practice of heating, tanzanite should not be exposed to high heat, which could potentially alter its color or cause damage. Professional cleaning is recommended for valuable tanzanite pieces.
In general, all birthstone jewelry should be stored in a soft cloth or lined jewelry box to prevent scratches and damage. Regular inspection of settings is also recommended to ensure the stones are secure.
Conclusion
The December birthstones—turquoise, zircon, and tanzanite—offer a diverse and captivating selection for those born in the last month of the year. From the ancient, protective turquoise with its rich history in Native American culture, to the brilliant, fire-filled zircon that has been prized for centuries, to the modern, exclusive tanzanite from Tanzania, each gemstone tells a unique story. Their geological origins span the globe, from the arid regions of the American Southwest to the volcanic soils of East Africa. Their gemological properties vary widely, from the soft, opaque turquoise to the hard, cleavable zircon and the trichroic tanzanite, each requiring specific care to preserve its beauty. While their symbolic meanings range from protection and wisdom to transformation, their shared characteristic is the stunning blue color that defines the winter month of December. This trio of gemstones ensures that every individual born in December can find a stone that resonates with their personal style, history, and belief system.