For those born in the final month of the year, December offers a unique trio of birthstones, each distinguished by its own captivating shade of blue and rich history. The birthstones for December are Turquoise, Zircon, and Tanzanite. While all are celebrated for their blue hues, they vary significantly in their geological origins, physical properties, and cultural significance. This article explores the distinct characteristics of each December gemstone, providing a comprehensive overview for gemstone enthusiasts, jewelry buyers, and students of gemology.
History and Lore
The association of specific gemstones with calendar months has evolved over centuries, with traditions rooted in ancient beliefs and later formalized by jewelers and gemological organizations. The modern concept of birthstones, as recognized today, has a history spanning several key developments.
The first official birthstone chart in the United States was established by the National Association of Jewelers (now Jewelers of America). This standardization provided a foundational list that has been widely adopted. Over the decades, this chart has been revised to include new and significant gemstone discoveries. For example, a major update added alexandrite to June, citrine to November, and pink tourmaline to October as alternative options. Later, the American Gem Trade Association added tanzanite as a December birthstone, marking a significant change to the list after 50 years. Spinel was also added as an additional birthstone for August.
While the modern chart is prevalent in the United States, cultural variations exist. The traditional British chart, for instance, includes bloodstone for March and rock crystal for April as alternatives. Other systems, such as the Hindu Ayurvedic system and the Tibetan Mystical chart, are based on astrological signs or spiritual significance rather than calendar months. In the United States today, people often draw freely from both modern and traditional lists, selecting stones that appeal to them. Some traditional gems remain popular due to being less expensive or more readily available than their modern counterparts.
Turquoise
Turquoise has a history that stretches back millennia, particularly in the Southwestern United States. Native Americans were using turquoise over 2000 years ago, where ancient artists produced beads, pendants, inlay work, and small sculptures. This deep historical integration means turquoise remains an important part of Southwestern culture. Its use as a gemstone for thousands of years is well-documented, with bright blue turquoise being the most preferred color. It is most often set into sterling silver jewelry.
Zircon
Zircon is a bright gem with high luster, and many specimens produce a colorful fire that is similar to a diamond. This brilliance has made it a valued gemstone throughout history. While the provided sources do not detail its specific historical uses in the same way as turquoise, its properties have long been recognized by gemologists and jewelers.
Tanzanite
Tanzanite is a more recent addition to the gemological world, which explains its absence from older historical records. Its addition to the birthstone list in 1952 by the American Gem Trade Association was a significant event, as it was the first change to the official list in half a century. This timing coincided with the discovery of large deposits of other gems, which helped make birthstones more accessible. The discovery of large topaz deposits in Brazil, for example, greatly reduced the price of topaz around the same period. Tanzanite’s introduction reflects the dynamic nature of the gemstone market and the ongoing evolution of birthstone charts.
Geological Formation and Sources
Each of the December birthstones forms through distinct geological processes and is sourced from different regions of the world.
Turquoise
Turquoise is a blue to blue-green to yellowish green mineral. It is an opaque gemstone, which influences how it is cut and presented in jewelry. The sources indicate that turquoise is mined around the world. While specific mines are not listed, its global availability contributes to its status as an affordable gemstone for many people.
Zircon
Zircon is a distinct mineral known for its high luster and fire. The sources confirm that zircon is mined around the world, contributing to its availability as a birthstone option. The geological processes that form zircon are not detailed in the provided chunks, but its occurrence in various global locations is noted.
Tanzanite
Tanzanite, like the other December stones, is mined around the world. The sources do not provide specific geographic locations for its mining, but they emphasize that all three December birthstones have unique takes on the color blue and are sourced from various global locations. The addition of tanzanite to the birthstone list in 1952 suggests its sources were identified and brought to market around that time, making it a relatively modern gem in terms of commercial availability.
Gemological Properties
Understanding the physical and chemical properties of a gemstone is crucial for its identification, valuation, and care. The December birthstones vary significantly in these aspects.
Turquoise
Turquoise is characterized by its opacity, which means light does not pass through it. This property dictates its common cutting style; it is usually cut into cabochon shapes, often freeform, to maximize the use of the rough material rather than being cut into calibrated shapes and sizes. Its hardness is a key factor in its durability. According to the provided data, turquoise has a hardness of 6.5 to 7 on the Mohs scale. However, it is also noted that turquoise, along with pearl and opal, has a low hardness and is easily scratched. This indicates that while its hardness range is moderate, its practical durability is affected by its susceptibility to scratching.
Zircon
Zircon is a bright gem with high luster and produces a colorful fire similar to that of a diamond. This optical property, known as dispersion, gives zircon a brilliant sparkle. The provided sources list zircon's hardness as 6.5 to 7 on the Mohs scale, placing it in a similar durability range as turquoise. However, the sources also note that zircon is prone to breakage, which is an important consideration for jewelry settings.
Tanzanite
Tanzanite is the third December birthstone, known for its blue to purple color. Its hardness is listed as 6.5 to 7 on the Mohs scale, matching the hardness of turquoise and zircon. Like zircon, tanzanite is noted to have perfect cleavage, meaning it will break easily if struck along certain planes. This property requires careful handling and setting in jewelry to protect the stone from impact.
The following table summarizes the key gemological properties for the December birthstones based on the provided sources:
| Gemstone | Color | Hardness (Mohs Scale) | Key Physical Properties |
|---|---|---|---|
| Turquoise | Blue to blue-green to yellowish green | 6.5 - 7 | Opaque; often cut as cabochons; prone to scratching |
| Zircon | Bright, with high luster and fire | 6.5 - 7 | Prone to breakage; known for its diamond-like sparkle |
| Tanzanite | Blue to purple | 6.5 - 7 | Has perfect cleavage; breaks easily |
It is important to note that while hardness provides a general measure of scratch resistance, other factors like cleavage and toughness significantly impact a gemstone's overall durability. For example, a gemstone with perfect cleavage (like tanzanite) is more susceptible to breaking from a sharp blow than a gemstone with no cleavage, even if their hardness is similar.
Symbolism and Metaphysical Beliefs
Gemstones have long been attributed with symbolic meanings and metaphysical powers. These beliefs often stem from historical lore, cultural traditions, and the perceived properties of the stone.
Turquoise
Turquoise is deeply embedded in the cultural symbolism of the Southwestern United States. For Native American cultures, it has been a significant material for over two millennia, used in art and jewelry. Its enduring presence in this culture underscores its symbolic importance. While the sources do not specify modern metaphysical beliefs, its historical role suggests themes of protection, artistry, and cultural identity.
Zircon
Zircon’s primary symbolic association, as derived from the sources, is its visual similarity to diamond. Its high luster and fiery sparkle have made it a gem that symbolizes brilliance and clarity. The sources do not detail specific ancient beliefs or modern metaphysical claims for zircon, focusing instead on its gemological characteristics.
Tanzanite
The sources do not provide specific symbolic or metaphysical beliefs associated with tanzanite. However, its addition to the modern birthstone list in 1952 aligns it with contemporary interpretations of birthstones, which often link each month's gem to personality traits or life goals. As a newer gem, its symbolism may be more associated with modern gemology and marketing rather than ancient lore.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of any gemstone. The care instructions for a gemstone are directly linked to its physical properties, such as hardness, cleavage, and porosity.
Turquoise
Turquoise’s properties present specific care challenges. Its hardness of 6.5 to 7 on the Mohs scale means it is moderately resistant to scratching but can be damaged by harder materials. More critically, the sources indicate that turquoise has a low hardness and is easily scratched. This suggests that even everyday wear can accumulate fine scratches on the surface. To clean turquoise, it is best to use warm water, mild soap, and a soft brush. Avoid ultrasonic cleaners, steam cleaners, and harsh chemicals, which can damage the stone or its surface treatment. It should also be stored separately to prevent scratching by other jewelry.
Zircon
Zircon has a hardness of 6.5 to 7, making it relatively durable, but the sources explicitly state it is prone to breakage. This means that while it resists scratching, it can fracture from impact due to its cleavage properties. Care for zircon should involve protecting it from hard blows. Cleaning can be done with warm soapy water and a soft brush. Ultrasonic cleaners are generally safe for zircon, but caution is advised due to its potential for breakage. Steam cleaning is not recommended.
Tanzanite
Tanzanite has a hardness of 6.5 to 7 but is noted to have perfect cleavage, making it susceptible to breaking. This is a critical factor for its care. It should be handled with care to avoid impacts and stored in a padded jewelry box or a soft cloth to prevent scratching and breakage. Cleaning tanzanite should be done with warm soapy water and a soft brush. It is not recommended to use ultrasonic cleaners or steam cleaners, as the vibrations and heat can cause the stone to crack along its cleavage planes.
Conclusion
The December birthstones—Turquoise, Zircon, and Tanzanite—offer a diverse palette of blue hues and distinct characteristics. Turquoise carries a deep cultural history, particularly in the Southwestern United States, and is valued for its opaque, often sky-blue color. Zircon is prized for its brilliant sparkle and fire, closely mimicking the appearance of a diamond. Tanzanite, a more recent discovery, adds a unique blue-to-purple variety to the December options. All three stones share a similar hardness range on the Mohs scale (6.5-7), but their durability varies due to factors like cleavage and susceptibility to scratching. Understanding these differences in history, geology, gemology, and care allows individuals to make informed choices when selecting jewelry featuring these captivating December gems.