The month of December is uniquely represented by three distinct and captivating birthstones: turquoise, zircon, and tanzanite. Each of these gems offers a unique interpretation of the color blue, providing a diverse palette for those born in the final month of the year. Turquoise, with its ancient history and opaque, sky-blue hue, contrasts with zircon, a brilliant and fiery gem that can mimic the sparkle of a diamond. Rounding out the trio is tanzanite, the newest addition to the December birthstone list, known for its mesmerizing trichroic color shift. Together, these stones form a rich tapestry of geological formation, historical significance, and cultural symbolism. This article explores the origins, properties, lore, and care of these three remarkable December birthstones, drawing exclusively from the provided sources to offer an expert perspective for gemstone enthusiasts and jewelry buyers alike.
History and Lore: From Ancient Talismans to Modern Traditions
The history of December's birthstones is as varied as the gems themselves, spanning millennia and continents. Turquoise is arguably the oldest of the three, with a documented history of use exceeding two millennia in the Southwestern United States. According to the sources, Native Americans were using turquoise over 2000 years ago, crafting beads, pendants, inlay work, and small sculptures. This ancient practice established turquoise as an enduring cultural and artistic material in the region, where it remains important to this day.
In contrast, zircon has a more recent history as a designated birthstone. The sources indicate that zircon replaced lapis lazuli as a modern birthstone for December in 1952. Prior to this, its high luster and colorful fire made it a popular alternative to diamond. The gem’s historical use as a diamond simulant is notable; many specimens of zircon produce a fire similar to that of a diamond, making it a valued gem in its own right for centuries.
Tanzanite is the most recent addition to the December birthstone list. The sources identify it as the newest birthstone for the month. Its discovery and subsequent rise to prominence are relatively modern phenomena, contributing to its status as a contemporary choice for December babies.
The establishment of modern birthstone lists is a key factor in how these gems are perceived today. The sources note that topaz, another gem sometimes associated with November and December, was added to most birthstone lists in 1952. This historical context is important for understanding the evolution of the December trio, as the lists have been periodically updated to include new discoveries and reflect changing market availability. The 1952 update, which also saw the inclusion of zircon, marks a significant milestone in the standardization of birthstones for December.
Geological Formation and Sources
Understanding where these gems come from provides insight into their rarity, value, and unique characteristics. Each of the three December birthstones forms under different geological conditions and is sourced from specific regions around the world.
Turquoise is an opaque mineral, a hydrous phosphate of copper and aluminum. Its formation typically occurs in arid regions where acidic, copper-rich groundwater seeps through and reacts with minerals containing aluminum and phosphorus, such as feldspars and apatite. Over long periods, this process creates nodules and veins of turquoise in host rock. The sources mention that turquoise is mined around the world, but its historical and cultural significance is deeply tied to the Southwestern United States, where it has been used by Native American cultures for thousands of years. The gem’s opaque nature means it is rarely transparent and is almost always cut into cabochons, often in freeform shapes to maximize the yield from the rough material.
Zircon is a zirconium silicate mineral that forms in a variety of geological environments. It is a common accessory mineral found in igneous, metamorphic, and sedimentary rocks. The sources do not specify particular mining locations for zircon, but they do note that most natural zircons are yellow, red, or brown. The vibrant blue zircon that is popular today is typically the result of heat treatment applied to these naturally occurring brownish stones. The sources state that about 80% of the zircons sold today are blue, with this color produced by treatment. This indicates that while natural zircon is found in various colors, the market is dominated by treated material, particularly the blue variety favored for December.
Tanzanite is a trade name for the blue to violet variety of the mineral zoisite. It is found in only one location in the world: the Merelani Hills of Northern Tanzania, near the base of Mount Kilimanjaro. This geographic exclusivity contributes significantly to its value and allure. The sources confirm that tanzanite is mined in this specific region. The gem’s characteristic color is often enhanced through heat treatment, which is a standard industry practice. The sources note that most tanzanite sold in jewelry today has a blue to bluish purple to bluish violet color that is produced by heat treatment. This treatment is used to transform the naturally occurring brownish or yellowish zoisite into the coveted blue-violet hue.
Gemological Properties
A detailed examination of the physical and optical properties of turquoise, zircon, and tanzanite reveals the scientific basis for their use in jewelry and their respective care requirements. The following table summarizes key gemological data extracted from the provided sources.
| Gemstone | Chemical Composition / Type | Typical Colors | Hardness (Mohs Scale) | Key Optical / Physical Properties |
|---|---|---|---|---|
| Turquoise | Hydrous phosphate of copper and aluminum | Blue to blue-green to yellowish green | 5 - 6 (Low hardness) | Opaque; often cut as cabochons; easily scratched. |
| Zircon | Zirconium silicate (ZrSiO₄) | Natural: yellow, red, brown; Treated: blue (most popular), green, others | 6.5 - 7.5 | High luster; high refractive index; produces fire similar to diamond; prone to breakage. |
| Tanzanite | Zoisite (Calcium aluminum hydroxyl silicate) | Blue to bluish violet (from heat treatment); trichroic (shows blue, violet, and red-brown) | 6.5 - 7 | Perfect cleavage in one direction; color changes with viewing angle (trichroism). |
Turquoise is characterized by its opacity and relatively low hardness, ranging from 5 to 6 on the Mohs scale. This softness, combined with its porous nature, makes it susceptible to scratching and damage from chemicals. Its color spectrum, from sky blue to greenish hues, is determined by the presence of copper (blue) and iron (green). The sources emphasize that bright blue turquoise is the most preferred color. Due to its opacity, turquoise is almost exclusively cut into cabochons, a practice that highlights its color and often incorporates the natural matrix (the host rock) as part of the gem’s design.
Zircon possesses gemological properties that make it a standout. It has a high luster and a high refractive index, which contributes to its brilliance and fire. The sources describe it as a "bright gem with high luster" that can produce a colorful fire similar to a diamond. With a hardness of 6.5 to 7.5, it is relatively durable for jewelry, though the sources note it is "prone to breakage." This susceptibility is likely due to its crystal structure and potential for inclusions. The vast majority of blue zircon on the market is the result of heat treatment applied to brownish natural zircons. The sources explicitly state that "about 80% of the zircons sold today are blue, with the color produced by treatment."
Tanzanite is distinguished by its trichroism, a property where the gem displays three different colors when viewed from three crystallographic directions. The sources describe this feature: "Its color has an interesting feature - it changes depending upon the angle of viewing." Typically, tanzanite shows blue, violet, and reddish-brown hues. Its hardness is similar to zircon, ranging from 6.5 to 7, but it has "perfect cleavage in one direction," making it more susceptible to breakage if struck with force. Like zircon, the vibrant blue color of tanzanite is almost always the result of heat treatment, which is used to eliminate the brownish component and enhance the blue and violet tones.
Symbolism and Metaphysical Beliefs
Across cultures and throughout history, gemstones have been imbued with symbolic meaning and metaphysical powers. While the provided sources offer limited information on the symbolism of these specific December birthstones, some general beliefs can be inferred from broader gemological and cultural contexts, though these should be approached with the understanding that they are not explicitly detailed in the sources.
Turquoise has long been associated with protection, health, and good fortune. Its use in Native American culture for over 2000 years suggests a deep-rooted spiritual significance, likely connected to the sky and water due to its color. In many traditions, turquoise is considered a stone of communication and peace, believed to promote emotional balance and ward off negative energy.
Zircon, with its diamond-like sparkle, has historically been linked to wisdom, prosperity, and honor. Its ability to inspire confidence and clarity of thought is a common belief among those who ascribe to crystal healing. The bright, fiery nature of zircon is often seen as a symbol of light and energy, believed to protect the wearer and attract abundance.
Tanzanite, as a modern discovery, has quickly accumulated its own set of metaphysical associations. It is often called the "stone of transformation," believed to facilitate spiritual awakening and higher consciousness. Its unique color change is thought to symbolize the connection between the physical and spiritual realms, offering protection and promoting a calm, meditative state. However, it is important to note that these specific symbolic interpretations are not explicitly detailed in the provided source material, which focuses more on the physical and historical aspects of the gems.
Care and Cleaning
The practical care of gemstone jewelry is essential for preserving its beauty and longevity. The differing physical properties of turquoise, zircon, and tanzanite necessitate specific care instructions to avoid damage.
Turquoise requires the most careful handling among the three December birthstones. With a low hardness of 5-6 on the Mohs scale and a porous structure, it is easily scratched and can be damaged by chemicals, including acids, cosmetics, and even perspiration. The sources note that turquoise has a "low hardness and is easily scratched." Cleaning should be done with a soft, dry cloth. If necessary, mild soap and lukewarm water can be used, but the piece must be dried thoroughly and immediately. Ultrasonic cleaners and steam cleaners are never recommended for turquoise, as the vibrations and heat can cause cracks or discoloration. It is also advisable to remove turquoise jewelry before engaging in physical activities or household chores to prevent impact and chemical exposure.
Zircon, while harder than turquoise, is not without its vulnerabilities. The sources identify it as "prone to breakage." This means that while it can withstand everyday wear, it should be protected from sharp blows and extreme temperature changes, which can cause fractures. Cleaning zircon jewelry is relatively straightforward: use warm, soapy water and a soft brush. Ultrasonic cleaners are generally safe for zircon, but it is always best to consult with a jeweler, especially if the stone has inclusions or has been treated. As with all gemstones, avoid harsh chemicals and sudden temperature shifts.
Tanzanite presents a unique challenge due to its perfect cleavage. The sources state that tanzanite "has perfect cleavage and will break easily." This makes it more fragile than zircon and significantly more fragile than turquoise in terms of impact resistance. Tanzanite jewelry should be stored separately in a soft cloth or padded box to avoid scratches from other gems. Cleaning should be done with a soft brush, mild soap, and lukewarm water. Avoid ultrasonic cleaners and steam, as the vibrations and heat can exploit the cleavage planes and cause the stone to crack or break. Due to its relative fragility, tanzanite is best suited for pieces that are not subjected to daily wear, such as earrings or pendants, rather than rings or bracelets.
Conclusion
The December birthstones—turquoise, zircon, and tanzanite—offer a compelling study in diversity. From the ancient, opaque turquoise cherished by Native American cultures for over two millennia, to the brilliant, diamond-like zircon that became a modern birthstone in 1952, to the newly discovered, color-shifting tanzanite from a single valley in Tanzania, each gem tells a unique story of geology, history, and human appreciation. Their gemological properties, from turquoise’s softness to zircon’s fire and tanzanite’s cleavage, dictate their use in jewelry and the care they require. While their symbolic meanings vary, they collectively represent the color blue in its many facets, providing those born in December with a rich selection of stones that are as beautiful as they are varied in origin and character. Understanding their distinct characteristics allows for informed choices in both appreciation and purchase, ensuring these gems can be cherished for generations to come.