The month of December is uniquely represented in the modern birthstone chart by three distinct gems: Turquoise, Zircon, and Tanzanite. Unlike months with a single stone, December offers a palette of blue hues, allowing individuals to choose a birthstone that aligns with their personal style and preference. These three minerals, formed under vastly different geological conditions and spanning different eras of human history, collectively tell a story of cultural significance, scientific fascination, and modern gemological innovation. From the ancient sky-blue turquoise cherished by civilizations for millennia, to the fiery brilliance of zircon that once mimicked diamond, to the recent discovery of tanzanite with its captivating color-shift, each stone offers a unique narrative. This article delves into the history, formation, properties, and symbolism of these three celebrated December birthstones, providing a comprehensive guide for gemstone enthusiasts and jewelry buyers alike.
History and Lore: A Journey Through Time
The historical significance of the December birthstones is as varied as the stones themselves, reflecting their diverse origins and cultural adoption.
Turquoise stands as the most ancient of the trio, with a documented history of use spanning thousands of years. In the Southwestern United States, Native American cultures were utilizing turquoise over 2,000 years ago, creating beads, pendants, intricate inlay work, and small sculptures. The stone remains an integral part of Southwestern cultural heritage today. Beyond the Americas, turquoise has been a prized gemstone in civilizations across the globe, valued for its distinctive color and believed protective qualities. Its enduring popularity is a testament to its timeless appeal.
Zircon carries a history of confusion and mistaken identity, primarily due to its exceptional brilliance. For centuries, zircon was used as a diamond simulant because of its high luster and ability to produce a colorful fire similar to diamond. This historical role often led to its undervaluation. However, the stone has a firm place in the modern birthstone calendar. According to historical records, zircon replaced lapis lazuli as a modern birthstone for December in 1952. This change was part of a broader update to the official birthstone list, reflecting shifting market availability and gemological understanding.
Tanzanite is the newest addition to the December birthstone family, a gemstone of recent discovery that has rapidly ascended to prominence. It entered the gemstone market in the late 1960s and was officially added to the birthstone list in 1952, alongside zircon. Its origin story is specific and dramatic; it is found in only one location on Earth—northern Tanzania. This geographic rarity, coupled with its striking color, has cemented its status as a modern classic. Unlike the ancient lore of turquoise or the historical confusion surrounding zircon, tanzanite's story is one of contemporary gemology and marketing, quickly becoming a symbol of luxury and exclusivity.
The journey to the modern birthstone list for these stones was solidified in 1952, a pivotal year for gemstone standardization. This update by the jewelry industry brought clarity and choice to December-born individuals, offering three distinct blue-hued options that continue to dominate the market today.
Geological Formation and Sources
The origins of these three gems are geographically and geologically distinct, contributing to their rarity and unique characteristics.
Turquoise is a phosphate mineral that forms in arid regions where acidic, copper-rich groundwater interacts with aluminum- and phosphorus-bearing minerals. The most significant sources are found in the Southwestern United States, particularly in Arizona and New Mexico, where ancient Native American cultures first discovered and utilized the stone. Other notable sources include Iran and Egypt, where turquoise has been mined for centuries. The stone is typically found in massive, nodular forms rather than in well-defined crystals, which influences how it is cut and set.
Zircon is a zirconium silicate mineral that forms in the cooling of magma. It is one of the oldest minerals on Earth, with some crystals dating back billions of years. While found in many locations worldwide, the most significant commercial sources for gem-quality zircon are in Cambodia, Sri Lanka, and Australia. Australian zircon, particularly from the state of New South Wales, is known for its high quality. The stone's formation in igneous and metamorphic rocks means it is often recovered as a byproduct of mining for other minerals, such as tin and diamonds.
Tanzanite has the most restricted and unique source of the three. It is found exclusively in a small, four-square-kilometer area in the Merelani Hills of northern Tanzania, near Mount Kilimanjaro. This incredible geographic limitation makes it over a thousand times rarer than diamond. Tanzanite is a variety of the mineral zoisite and is formed by the intense heat and pressure of tectonic plate movement in the East African Rift Valley. The specific geological conditions required for its formation are so rare that it is widely believed to be a one-time geological event, leading to the marketing phrase "a generation's worth of tanzanite left to be mined."
The following table summarizes the primary sources for each December birthstone:
| Birthstone | Primary Mineral Family | Key Geological Process | Major Mining Locations |
|---|---|---|---|
| Turquoise | Phosphate | Copper-rich water interacting with aluminum minerals | Southwestern USA (Arizona, New Mexico), Iran, Egypt |
| Zircon | Silicate (Zirconium) | Cooling of magma; igneous/metamorphic formation | Cambodia, Sri Lanka, Australia |
| Tanzanite | Silicate (Zoisite variety) | Tectonic heat and pressure | Northern Tanzania (Merelani Hills) |
Gemological Properties
Understanding the physical and optical properties of these gems is essential for identification, valuation, and care.
Turquoise is prized for its opaque, waxy luster. Its color ranges from blue to blue-green to yellowish green, with bright, even blue being the most valued. As an opaque stone, it is almost exclusively cut into cabochons—smooth, rounded domes—often in freeform shapes to maximize the use of the rough material. Turquoise has a relatively low hardness on the Mohs scale, making it susceptible to scratching, and it can be porous, often requiring stabilization (treatment with a clear resin) to improve durability and color consistency.
Zircon is renowned for its exceptional brilliance and fire, which can rival that of diamond. It has a high refractive index and strong dispersion, giving it a spectacular light performance. Natural zircon is most commonly found in yellow, red, or brown hues. However, the vibrant blue zircon that dominates the market is typically the result of heat treatment applied to brownish zircon. This process, when performed at high temperatures (often above 1,000°C), can produce a stable blue color. Zircon is a relatively hard gemstone, ranking 6.5 to 7.5 on the Mohs scale, but it is brittle and can be prone to breakage due to its perfect cleavage in two directions.
Tanzanite is a pleochroic gemstone, meaning it displays different colors when viewed from different crystal directions. Its most characteristic color is a blue to bluish purple to bluish violet, which is almost always the result of heat treatment applied to the brownish-yellow zoisite as mined. This treatment is a standard industry practice and is widely accepted. Like zircon, tanzanite has perfect cleavage, making it fragile and requiring careful handling during cutting and setting. Its hardness is similar to zircon, at 6 to 7 on the Mohs scale.
A critical note on durability applies to all three stones. While beautiful, they require careful handling. Turquoise has a low hardness and is easily scratched. Zircon and tanzanite are both prone to breakage due to their perfect cleavage. This means that while they can be set in jewelry, they are not ideal for rings that will be subjected to daily wear and impact, such as engagement rings. They are better suited for pendants, earrings, and occasional-wear rings.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, each of the December birthstones carries a rich tapestry of symbolic meaning and metaphysical belief, often rooted in ancient traditions and folklore.
Turquoise is universally recognized as a stone of protection, healing, and good fortune. Across many cultures, it has been believed to ward off negative energy, bring peace to the wearer, and even change color to warn of impending danger or illness. Its connection to the sky and water in Native American lore symbolizes life, fertility, and spiritual grounding. In modern crystal healing, turquoise is associated with the throat chakra, promoting honest communication and self-expression.
Zircon, despite its historical role as a diamond substitute, has its own set of attributes. It is often linked to wisdom, honor, and purity. In some traditions, it is believed to aid in sleep, promote prosperity, and foster a sense of spiritual grounding. The blue variety, which is most common today, is sometimes associated with clarity of thought and calmness, making it a popular stone for those seeking mental focus and emotional balance.
Tanzanite, as a relatively new stone, has developed modern metaphysical associations. It is often called the "stone of transformation," believed to facilitate a higher consciousness and spiritual awakening. Its unique color shift is seen as a symbol of seeing beyond the mundane and connecting with the divine. In contemporary crystal practices, tanzanite is associated with the crown and third-eye chakras, intended to enhance intuition, psychic abilities, and a connection to one's higher self.
It is important to note that while these symbolic meanings are deeply held by many, they are part of cultural and metaphysical traditions rather than scientifically verified properties. For gemstone enthusiasts, these beliefs add a layer of personal significance to the stones, enhancing their appeal beyond mere aesthetics.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of these December birthstones, given their specific physical properties.
Turquoise requires gentle care due to its porosity and lower hardness. It should be cleaned with only a soft, damp cloth. Avoid all chemicals, including household cleaners, cosmetics, and even some soaps, as they can penetrate the stone and cause discoloration or damage the stabilizing treatment. Ultrasonic cleaners and steam cleaners are strictly forbidden. Store turquoise jewelry separately to prevent scratching by harder gems.
Zircon and Tanzanite share similar care requirements due to their perfect cleavage and moderate hardness. They should be cleaned using warm water, a mild soap, and a soft brush. It is crucial to avoid sudden temperature changes, as thermal shock can cause fractures along their cleavage planes. Never use an ultrasonic cleaner for zircon or tanzanite, as the vibrations can easily cause the stone to crack or split. The same caution applies to steam cleaning. When storing, keep these stones in a soft cloth or separate compartment in a jewelry box to protect them from harder gems and accidental impacts.
For all three stones, the best practice is to put on jewelry last when dressing and take it off first when undressing. This simple habit minimizes exposure to chemicals, perfumes, and physical trauma, ensuring the gems remain vibrant and intact for generations.
Conclusion
The December birthstones—Turquoise, Zircon, and Tanzanite—offer a remarkable trio of gems that cater to a wide range of tastes and preferences. From the ancient, protective allure of turquoise to the brilliant, diamond-like fire of treated zircon and the transformative, color-shifting beauty of tanzanite, each stone provides a unique connection to history, geology, and personal symbolism. While they vary in origin, durability, and market presence, they are united by their stunning blue colorations and their official status as the birthstones for the final month of the year. Understanding their individual stories, properties, and care requirements allows enthusiasts and buyers to make informed choices, ensuring that the selected gemstone is not only beautiful but also cherished and preserved for years to come.