The final month of the year is uniquely represented by a trio of gemstones, each offering a distinct interpretation of the color blue. For those born in December, the birthstones are Turquoise, Zircon, and Tanzanite. This diverse selection provides a remarkable range of choices, from ancient, opaque turquoise to the brilliant fire of zircon and the color-shifting allure of tanzanite. These stones are mined across the globe, from the arid landscapes of the American Southwest to the mineral-rich soils of Africa and Asia, and each carries a unique history, set of properties, and cultural significance. This article explores the geological formation, gemological characteristics, historical lore, and practical care of these three remarkable December birthstones, providing a comprehensive guide for collectors, jewelry enthusiasts, and students of gemology.
History and Lore
The journey of December's birthstones to their modern status is a story of tradition, trade, and official recognition. The concept of birthstones has ancient roots, with associations between gems and zodiac signs or calendar months dating back centuries. However, the standardized list used in the United States today was established much more recently.
Turquoise: An Ancient Stone of the Americas
Turquoise holds one of the longest histories as a gemstone among the December trio. It has been used as a gem for thousands of years, with evidence of its use by Native Americans in the southwestern United States dating back over 2000 years. Ancient artists in this region produced beads, pendants, inlay work, and small sculptures from this material, and it remains an important part of Southwestern culture today. Its use was not limited to North America; turquoise has been valued across many ancient cultures, though the provided sources focus on its deep connection to the Americas.
Zircon: A Diamond Alternative with a Modern Date
Zircon has a long history as a gemstone, prized for its high luster and colorful fire, which made it a popular alternative to diamond in historical jewelry. Its status as a modern birthstone, however, is more recent. According to the sources, zircon replaced lapis lazuli as an official December birthstone in 1952. This change was part of a broader update to the birthstone list by the National Association of Jewelers (now Jewelers of America). The addition of zircon was significant, offering a bright, brilliant option for December babies. The sources note that at the time of its addition, topaz was a relatively costly gem, and the discovery of large deposits in Brazil later helped reduce the price of many colored gemstones, though the text does not specify if this directly influenced zircon's market.
Tanzanite: A Newcomer to the List
Tanzanite is the newest addition to the December birthstone family. Its inclusion marked a significant update to the traditional list, as it was added by the American Gem Trade Association. This addition was the first major change to the official birthstone chart in 50 years, highlighting the evolving nature of the gemstone market and the discovery of new, desirable materials. The sources describe tanzanite as the newest birthstone for the month, a gem whose unique color and recent discovery have made it a modern favorite.
Geological Formation and Sources
Understanding where these gems come from provides insight into their rarity, value, and unique characteristics. Each of the December stones forms under different geological conditions and is mined in specific regions of the world.
Turquoise: An Hydrated Phosphate Mineral
Turquoise is a blue to blue-green to yellowish green mineral. It is an opaque gem, which is why it is typically cut into cabochon shapes rather than faceted. The sources do not provide a detailed chemical formula or formation process for turquoise, but they emphasize its global mining locations. Turquoise is mined around the world, and the provided sources specifically highlight its historical and ongoing use in the Southwestern United States, where it remains a culturally significant material.
Zircon: A Zirconium Silicate with a Complex History
Zircon is a zirconium silicate (ZrSiO₄) and is one of the oldest minerals on Earth, often found as crystals in igneous and metamorphic rocks. The sources note that most natural zircons are yellow, red, or brown. However, the vibrant blue zircon most commonly seen in jewelry today is typically the result of heat treatment. The sources state that about 80% of the zircons sold today are blue, with this color produced by treatment. This heat treatment can also transform natural zircon into green and many other colors, as illustrated by a described color suite of stones including rose, peach, yellow, green, blue, honey, white, champagne, cognac, and mocha. While the specific mining locations for zircon are not detailed in the provided chunks, the sources mention that gemstones in general are mined around the world.
Tanzanite: A Blue Variety of Zoisite
Tanzanite is a blue to bluish purple to bluish violet variety of the mineral zoisite. Its color is a defining feature, but it is also almost always the result of heat treatment. The sources explain that most tanzanite sold in jewelry today has its color produced by heat treatment, which transforms the naturally brownish material into the desirable blue hue. The gem's most fascinating characteristic is its color-change effect, where the color appears to shift depending on the angle of viewing. This pleochroic property is a key part of its appeal. The sources confirm that tanzanite is mined, but like the others, specific locations are not detailed in the provided text.
Gemological Properties
The physical and optical properties of a gemstone determine its durability, brilliance, and overall value. For December's birthstones, these properties vary widely, influencing how they are worn and cared for.
Hardness and Durability
Gemological hardness is measured on the Mohs scale, which ranges from 1 (softest) to 10 (hardest). The durability of a gemstone is also affected by its cleavage (the tendency to break along flat planes) and its overall toughness.
- Turquoise is noted for having a low hardness, which makes it easily scratched. As an opaque gem, it is less prone to the type of cleavage that affects transparent stones but is susceptible to surface damage from abrasion.
- Zircon is a relatively hard gemstone, with a Mohs hardness of 6.5 to 7.5. However, the sources caution that zircon is prone to breakage. This is due to its crystal structure, which can make it brittle despite its hardness. It is not listed as having perfect cleavage, but its proneness to breakage is a key consideration for jewelry design and wear.
- Tanzanite has a Mohs hardness of 6.5 to 7, similar to zircon. The sources specifically state that tanzanite has perfect cleavage and will break easily. This makes it a gem that requires careful handling and protective settings, especially in rings or bracelets where impact is more likely.
Color and Optical Properties
Color is the most important factor for most colored gemstones, and for these December stones, it is a defining characteristic.
- Turquoise is prized for its opaque, sky-blue to greenish-blue color. The sources indicate that bright blue turquoise is the most preferred color. Its opacity means it does not display the brilliance of faceted gems but offers a rich, waxy luster when polished.
- Zircon is known for its high luster and "colorful fire," a reference to its strong dispersion, which is similar to that of diamond. This fire separates white light into its spectral colors, creating a sparkling effect. While natural zircon is often yellow, red, or brown, the treated blue variety is the most popular, accounting for an estimated 80% of the zircon on the market.
- Tanzanite is celebrated for its unique blue-to-violet color, which exhibits a dramatic change depending on the viewing angle. This pleochroism is a hallmark of the gem. The color is almost always enhanced by heat treatment, which removes the brownish undertones and reveals the vibrant blue hue.
The following table summarizes the key gemological properties of the three December birthstones as described in the provided sources:
| Gemstone | Typical Colors | Hardness (Mohs) | Cleavage | Key Optical Property |
|---|---|---|---|---|
| Turquoise | Blue to blue-green to yellowish green | Low (not specified, but noted as easily scratched) | Not specified | Opaque |
| Zircon | Natural: Yellow, red, brown. Treated: Blue, green, etc. | 6.5 - 7.5 | Not specified (prone to breakage) | High luster, high dispersion ("fire") |
| Tanzanite | Blue to bluish violet (heat-treated) | 6.5 - 7 | Perfect (breaks easily) | Strong pleochroism (color change) |
Symbolism and Metaphysical Beliefs
While the provided sources are primarily focused on gemological and historical facts, they touch upon some of the symbolic meanings and beliefs associated with these stones, particularly in a modern context.
Turquoise, with its millennia-long history, is deeply embedded in the cultural and spiritual life of Southwestern Native American tribes, where it is more than just a decorative material. While the sources do not detail specific metaphysical properties, its enduring use in art and jewelry suggests a profound cultural significance.
Zircon, in its bright, fiery form, has historically been associated with light and clarity. Its use as a diamond substitute speaks to its value and beauty, and it is often linked to prosperity and wisdom in various metaphysical traditions, though these specific beliefs are not detailed in the provided chunks.
Tanzanite, as a very new gemstone (discovered in the 20th century), has quickly developed modern symbolic associations. The sources do not specify these, but its unique color-shifting property is often interpreted as a stone of transformation and spiritual awakening in contemporary crystal healing circles. The general description of December birthstones as having a "unique take on the color blue" allows for personal interpretation of their symbolic meaning, choosing the stone that "best fits your style."
Care and Cleaning
The different physical properties of these gems dictate specific care instructions to ensure their longevity. Proper maintenance is essential, especially for stones with lower hardness or perfect cleavage.
Turquoise is the most delicate of the three due to its low hardness and porous nature. It should be protected from chemicals, cosmetics, and even perspiration, which can cause discoloration. 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 that could cause impact or exposure to harsh substances.
Zircon, while harder than turquoise, is prone to breakage. It should be protected from sharp blows and extreme temperature changes, which can cause fracturing. Standard cleaning with warm water, a mild soap, and a soft brush is safe. However, due to its brittleness, it is not ideal for rings worn daily or in settings that expose it to frequent impact.
Tanzanite is particularly challenging to care for due to its perfect cleavage and relatively low hardness. It is highly susceptible to breaking from a sharp blow. It should never be subjected to ultrasonic or steam cleaning, as the vibrations and heat can cause fractures. The safest method is warm, soapy water and a soft brush, with gentle handling. For this reason, tanzanite is often set in protective settings like bezels for rings and is best suited for earrings, pendants, and brooches.
For all three stones, the sources emphasize the importance of disclosure. When purchasing birthstone jewelry, it is critical to know whether the gem is natural, lab-created, or a simulant. The sources note that synthetic and imitation gems are common in commercial jewelry to reduce cost. Selling these without clear disclosure is a violation of trade guidelines. For collectors and buyers who prefer natural gems, this disclosure is essential.
Conclusion
The December birthstones—Turquoise, Zircon, and Tanzanite—offer a remarkable diversity of choice, united by their captivating shades of blue. From the ancient, opaque turquoise of the American Southwest to the brilliant, diamond-like fire of treated zircon and the color-shifting wonder of tanzanite, each gem tells a different story. Their histories are woven into the fabric of ancient cultures, modern trade, and official standardization, with zircon joining the list in 1952 and tanzanite becoming the newest addition after a half-century. Geologically, they are distinct: turquoise as a hydrated phosphate, zircon as a zirconium silicate, and tanzanite as a heat-treated variety of zoisite. Their gemological properties range from the soft and opaque to the hard yet brittle, dictating careful handling and specific cleaning methods. For those born in December, this trio provides not only a personal birthstone but a connection to a rich tapestry of geological time, human history, and enduring beauty.