The month of December is uniquely associated with three distinct and captivating birthstones: turquoise, tanzanite, and zircon. While each gem possesses its own geological origin, historical narrative, and gemological characteristics, they share a unifying theme of blue hues, ranging from the sky-like serenity of turquoise to the vivid violet-blue of tanzanite and the fiery brilliance of zircon. These stones offer a diverse palette for those born in the final month of the year, allowing for personal expression through color and style. This article delves into the rich history, formation, properties, and symbolism of these three December birthstones, providing a detailed exploration for gemstone enthusiasts, collectors, and anyone interested in the science and lore behind these remarkable gems.
Historical Significance and Lore
The journey of December’s birthstones through history is a testament to their enduring appeal. Turquoise, the oldest of the trio, boasts a lineage stretching back millennia. In the Southwestern United States, Native American cultures were using turquoise over 2000 years ago. Ancient artists in these regions crafted intricate beads, pendants, inlay work, and small sculptures from the stone, establishing it as a cornerstone of their cultural and artistic expression. This deep historical integration ensures that turquoise remains an important part of Southwestern culture today.
Zircon’s history is equally storied, though its modern birthstone status is more recent. For centuries, zircon has been prized for its remarkable brilliance and fire, which are so similar to a diamond’s that it was frequently used as a diamond alternative. This historical use underscores its value and visual appeal, even before its formal recognition as a birthstone. Zircon officially replaced lapis lazuli as a modern birthstone for December in 1952, a change that reflected evolving tastes and the gem’s increasing availability in the market.
Tanzanite is the newest addition to the December birthstone family. Its history is intrinsically linked to a specific geological event and a modern discovery. The gem was added to most official birthstone lists in 1952, the same year as zircon. However, its story begins with the formation of the Merelani Hills in Tanzania, the only known source of this unique gem. While its official recognition as a birthstone is a mid-20th-century event, its rapid ascent in popularity is a testament to its stunning color and unique properties.
Geological Formation and Global Sources
The origins of these stones are as varied as their colors, reflecting the diverse geological processes that create gemstones.
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. Over long periods, this interaction creates nodules and veins in host rocks. The primary sources of turquoise mentioned in the provided materials are located in the Southwestern United States, where it has been mined and used for thousands of years. The stone’s opacity and typical formation in nodules influence how it is cut and set, often favoring cabochon styles that highlight its unique matrix patterns.
Tanzanite is a variety of the mineral zoisite and is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This extreme rarity, with a known source confined to a very small geographic area, contributes significantly to its value and allure. The gem’s formation is linked to specific geological conditions involving the metamorphism of minerals, a process that created the unique blue-to-violet crystals.
Zircon is a zirconium silicate (ZrSiO₄) that forms in igneous and metamorphic rocks. It is a common mineral found in many geological environments, but gem-quality crystals suitable for faceting are rarer. The provided materials note that most natural zircons are yellow, red, or brown, but treatments can produce other colors. While specific mining locations are not detailed in the sources, the gem’s global presence is implied by its long history as a diamond simulant and its widespread availability in the gem market.
Gemological Properties and Characteristics
Understanding the physical and optical properties of these gems is essential for identification, appreciation, and care.
Turquoise is an opaque mineral, meaning light does not pass through it. Its color ranges from blue to blue-green to yellowish green, with bright blue being the most preferred. Due to its opacity and typical formation, it is most often cut into cabochons, frequently in freeform shapes to maximize the use of the rough material. On the Mohs scale of hardness, turquoise ranges from 5 to 6, making it relatively soft compared to many other gemstones. This softness, combined with its porous nature, requires careful handling.
Tanzanite is known for its dramatic color change, a pleochroic effect where the stone appears blue from one angle and violet from another. Most tanzanite sold in jewelry today exhibits a blue to bluish purple to bluish violet color, a hue that is often enhanced by heat treatment. While the provided sources do not specify its exact hardness, they indicate it is suitable for jewelry use. Its unique color and trichroic nature (displaying three different colors) make it a standout in the gem world.
Zircon is a brilliant gem with high luster and exceptional fire, often compared to that of a diamond. It has a high refractive index, which contributes to its sparkle. Zircon is available in a variety of colors; blue is the most popular, though most natural zircons are yellow, red, or brown. The blue color seen in about 80% of commercial zircons is produced through heat treatment. Zircon has a hardness of 7.5 on the Mohs scale, making it durable enough for most jewelry applications, though it can be brittle due to its crystal structure. The table below summarizes key properties of the three December birthstones based on the provided information.
| Birthstone | Color Range | Hardness (Mohs Scale) | Key Properties | Typical Cut |
|---|---|---|---|---|
| Turquoise | Blue, Blue-Green, Yellowish-Green | 5 - 6 | Opaque, often has a matrix | Cabochon (often freeform) |
| Tanzanite | Blue to Bluish Violet | Not specified (in sources) | Pleochroic (color change), often heat-treated | Faceted |
| Zircon | Blue (treated), Yellow, Red, Brown (natural) | 7.5 | High luster and fire, can be brittle | Faceted |
Symbolism and Metaphysical Beliefs
Across cultures and centuries, gemstones have been imbued with symbolic meaning and metaphysical properties. The December birthstones are no exception, each carrying a legacy of beliefs.
Turquoise is deeply connected to protection and healing. In the Southwestern United States, its use by Native Americans for over two millennia suggests a long-standing belief in its power. While the provided materials do not elaborate on specific modern metaphysical claims, its historical integration into cultural artifacts implies a significance beyond mere decoration, likely related to spiritual protection or connection to the earth and sky.
Tanzanite, as a relatively modern discovery, has accumulated contemporary metaphysical associations. The provided materials note that it is associated with protection, healing, and wisdom. This aligns with its unique, calming blue-violet hue, which is often linked to clarity of mind and spiritual insight in modern crystal healing practices.
Zircon (specifically blue zircon) is often associated with wisdom and clarity. Its diamond-like brilliance has historically linked it to concepts of purity and light. While the sources do not detail specific symbolic meanings for zircon, its historical use as a diamond simulant suggests it has long been valued for its beauty and perceived purity.
It is important to note that metaphysical beliefs are cultural and personal interpretations. The provided materials highlight these symbolic meanings as part of the gemstones' historical and cultural context, rather than as scientifically verified properties.
Care and Cleaning
Proper maintenance is crucial for preserving the beauty and longevity of these gemstones, given their distinct physical properties.
Turquoise, with its moderate hardness (5-6) and porous nature, is the most delicate of the three. It is susceptible to chemicals, oils, and even prolonged exposure to water, which can cause discoloration or damage. Cleaning should be done with a soft, dry cloth. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals. It is best to remove turquoise jewelry before activities like swimming, showering, or applying lotions and perfumes.
Tanzanite requires careful handling due to its perfect cleavage in one direction, meaning it can split along certain planes if struck with force. While not explicitly stated in the sources, this is a known property of zoisite. It is generally recommended to clean tanzanite with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and extreme temperature changes, which can cause damage.
Zircon, despite its hardness of 7.5, is brittle and can be easily chipped or abraded due to its crystal structure. It is sensitive to sudden temperature changes. The safest cleaning method is warm, soapy water with a soft brush. Ultrasonic cleaners are not recommended, as vibrations can cause fractures in already-fractured stones. Due to its brittleness, zircon should be stored carefully to avoid contact with harder gems that could scratch or chip it.
Conclusion
December’s birthstones—turquoise, tanzanite, and zircon—offer a remarkable trio of gems, each with a unique identity yet united by a spectrum of blue. Turquoise carries the weight of ancient history and cultural significance, especially in the American Southwest. Zircon boasts a long history as a prized gem with diamond-like fire, formally recognized as a birthstone since 1952. Tanzanite represents modern discovery and rarity, captivating the world with its vivid color and unique pleochroism. Together, they provide December-born individuals with a rich selection of stones that vary in hardness, treatment, and lore, ensuring there is a perfect gem to match any preference or style. Understanding their origins, properties, and care requirements allows for a deeper appreciation of these beautiful natural treasures.