December is unique in the calendar of birthstones. While most months are assigned a single gem, December boasts a quartet of official and widely recognized stones: Turquoise, Tanzanite, Blue Zircon, and Blue Topaz. This abundance reflects a historical evolution where new gemstones were added to traditional lists to provide greater variety and accessibility. All four gems share a unifying aesthetic—a palette of cool, wintry blues that mirror the season’s icy skies and deep twilight. Yet, each stone possesses a distinct geological origin, gemological profile, and cultural narrative. For the gemstone enthusiast, jewelry buyer, or student of gemology, understanding the nuances of these four blue gems is key to appreciating their collective and individual significance within the December birthstone tradition.
Historical Evolution and the Modern Birthstone List
The concept of birthstones is ancient, with roots often traced to the biblical description of Aaron’s breastplate in the Book of Exodus, which featured twelve gemstones representing the twelve tribes of Israel. Over centuries, these stones were associated with the twelve signs of the zodiac and later with the months of the year. The modern standardization of birthstones, however, is a more recent development, largely driven by the American jewelry industry in the early 20th century.
The National Association of Jewelers standardized the unofficial American birthstones in 1912, a list that combined historical customs with gemstones practical for commercial jewelry production. This list has been updated several times. In 1952, the Jewelry Industry Council of America added Zircon to December’s list. Tanzanite, a relative newcomer to the gem world, was added in 2002. Blue Topaz, while not part of the 1912 or 1952 official lists, has been embraced by the industry and is now widely recognized as a December birthstone, particularly in the United States.
The reason for December’s multiple birthstones is not definitively documented, but a common theory suggests it was to offer more affordable options. As new gemstone discoveries were made and commercial offerings evolved, the birthstone list adapted. This evolution allows individuals to choose a stone that not only resonates with their personal style but also fits their budget and desired level of durability for everyday wear.
Turquoise: The Ancient Stone of Protection
Turquoise is one of the oldest known gemstones, with a history spanning millennia. Its name derives from the French pierre turquoise, meaning "Turkish stone," reflecting its trade route through Turkey to Europe from its primary sources in Persia (modern-day Iran) and the Sinai Peninsula. From the earliest times, turquoise was a favored gem for amulets. Its relative ease of cutting and ability to hold inscriptions made it ideal for talismans. It was widely believed to possess protective powers against danger and to bring good fortune. In relationships, it was prized by lovers and married couples, thought to preserve friendship if given as a gift. A popular superstition held that turquoise could warn its wearer of approaching illness or danger by becoming pale.
Different cultures have imbued turquoise with specific meanings. Tibetans considered it a stone of fortune, health, and success, and it was so valued that it was often used as currency. Ancient Incas and Mayas offered turquoise as a gift to their gods. In the American Southwest, Native American tribes associated the gem with youth and strength. Today, turquoise is linked to protection, grounding, and a sense of calm, often sought as a steadying force during chaotic times.
Geological Formation and Sources: Turquoise is a hydrous phosphate mineral containing copper and aluminum. It forms in arid regions where acidic, copper-rich water percolates through aluminum-bearing rocks. The most famous sources historically were Persia (Iran) and the Sinai Peninsula. In the United States, significant deposits are found in the Southwest, particularly in Arizona and New Mexico.
Gemological Properties: Turquoise is known for its distinctive sky-blue to greenish-blue color, often with a unique, porous matrix of host rock (typically iron pyrite or other minerals) that creates characteristic "spiderweb" or "chicken wire" patterns. It is relatively soft, with a Mohs hardness of 5 to 6, making it susceptible to scratches and chemicals. It is typically cut en cabochon (a smooth, rounded dome) to showcase its color and matrix. High-grade turquoise with an even, vibrant color and minimal matrix is most valued.
Care and Cleaning: Due to its softness and porosity, turquoise requires careful handling. It should not be exposed to harsh chemicals, cosmetics, or prolonged sunlight, which can cause fading or discoloration. Clean it with a soft, damp cloth and mild soap; avoid ultrasonic cleaners and steam. It is best suited for jewelry that is not subjected to heavy daily wear, such as pendants and earrings, rather than rings worn constantly.
Tanzanite: The Rare Violet-Blue Marvel
Tanzanite is a gemological phenomenon, discovered in the 20th century and valued for its intense, saturated color. It was added to the official birthstone list in 2002, making it the newest of the December stones. Its meaning is often linked to transformation, growth, and new beginnings, with its shifting blue-violet tones symbolizing a step into new chapters with clarity and curiosity.
Geological Formation and Sources: Tanzanite is a variety of the mineral zoisite. It is found in only one location on Earth: the Merelani Hills of northern Tanzania, near the base of Mount Kilimanjaro. This extreme rarity—being mined in a specific region of just a few square kilometers—makes it significantly rarer than diamond. The gem's formation is linked to the tectonic activity that created the East African Rift Valley.
Gemological Properties: Tanzanite is prized for its strong pleochroism, displaying different colors (typically blue and violet) when viewed from different crystal directions. Its color ranges from a pure ultramarine to a violet-blue, often with a velvety appearance. It is relatively soft, with a Mohs hardness of 6.5 to 7, making it more durable than turquoise but still requiring care. It is almost always heat-treated to achieve its stable blue and violet hues; untreated zoisite is typically brownish-green. High-quality tanzanite is valued for its intense, even color and clarity.
Value and Rarity: As the rarest of the four December birthstones, tanzanite is also the most expensive. Its value is driven by its limited supply and high demand for its unique color. The mining area is finite, and experts estimate that the current deposits may be depleted within a few decades, further increasing its allure and value.
Care and Cleaning: While harder than turquoise, tanzanite is still relatively soft and can be brittle. It is prone to chipping and cracking from sharp blows. It should be protected from hard knocks and extreme temperature changes. Clean with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam, as the heat and vibrations can cause damage. Due to its relative fragility, it is often set in protective settings for rings, or used in pendants and earrings.
Zircon: The Brilliant Blue Diamond Alternative
Zircon should not be confused with the synthetic cubic zirconia (CZ). Natural zircon is a natural gemstone with a long history. It was added to the December birthstone list in 1952. Zircon is associated with clarity, wisdom, and a sense of balance, known for sharpening focus and boosting mental clarity.
Geological Formation and Sources: Zircon is a zirconium silicate mineral that forms in igneous and metamorphic rocks. It is a common mineral found in many locations worldwide, but gem-quality zircon is rarer. Major sources for blue zircon include Sri Lanka, Cambodia, and Myanmar. The blue color in gem zircon is typically achieved through heat treatment of brown or yellow zircon crystals.
Gemological Properties: Zircon is one of the highest-dispersion gemstones, meaning it exhibits exceptional brilliance and fire, rivaling that of diamond. Its refractive index is high, contributing to its sparkle. Blue zircon ranges in color from light to medium blue, often with a bright, clear appearance. It is relatively hard, with a Mohs hardness of 6.5 to 7.5, making it more durable than turquoise and tanzanite for everyday wear. However, zircon is brittle and can be prone to chipping due to its perfect cleavage in two directions. It is typically faceted to maximize its brilliance.
Value and Market: Zircon offers excellent visual impact for its price, making it a popular choice for mid-budget jewelry. Well-cut zircon can appear more brilliant than many other blue gems. Its value is determined by color, cut, clarity, and size, with larger, evenly colored stones being more valuable.
Care and Cleaning: Due to its brittleness and cleavage, zircon should be handled with care to avoid knocks and blows. It is stable under normal wearing conditions but can be damaged by extreme heat or rapid temperature changes. Clean with warm, soapy water and a soft brush. Avoid ultrasonic cleaners and steam, as the vibrations and heat can cause fractures.
Blue Topaz: The Durable and Accessible Winter Blue
Blue Topaz is the most durable of the December birthstones and has become a staple in American jewelry. While not part of the original 1912 list, its popularity has cemented its place as a modern December gem. It is the official state gem of Texas. Its meaning is not as deeply documented in historical lore as turquoise, but its cool, crisp blue is synonymous with winter.
Geological Formation and Sources: Topaz is a silicate mineral containing fluorine and aluminum. Natural blue topaz is rare; the vast majority of blue topaz on the market is colorless or pale topaz that has been irradiated and heat-treated to achieve its blue color. It is mined in various locations, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States.
Gemological Properties: Blue topaz is prized for its clarity and vibrant blue hues, ranging from sky blue (Swiss Blue) to a deeper, more saturated blue (London Blue). It has a Mohs hardness of 8, making it the hardest of the four December birthstones and highly suitable for everyday wear, including rings. It is typically faceted and can be found in large sizes, making it an excellent choice for statement pieces.
Value and Durability: Blue topaz is an affordable and accessible gemstone, offering significant visual appeal for a relatively low cost. Its high hardness and durability make it ideal for engagement rings and daily-wear jewelry, a recommendation often made by U.S. jewelry brands.
Care and Cleaning: With its high hardness and lack of cleavage, blue topaz is very easy to care for. It can be cleaned with warm, soapy water, ultrasonic cleaners, and steam. Its durability makes it a practical choice for active lifestyles.
Comparative Summary of December Birthstones
The following table summarizes the key gemological and practical differences between the four December birthstones, based on the provided information.
| Gemstone | Mohs Hardness | Key Characteristics | Primary Sources | Durability for Daily Wear |
|---|---|---|---|---|
| Turquoise | 5 - 6 | Often porous with a matrix; sky-blue to greenish-blue. | Iran, Sinai Peninsula, U.S. Southwest | Low (Best for occasional wear) |
| Tanzanite | 6.5 - 7 | Strong pleochroism (blue/violet); rich violet-blue. | Merelani Hills, Tanzania | Moderate (Protect from blows) |
| Zircon | 6.5 - 7.5 | High brilliance & fire; bright clear blue. | Sri Lanka, Cambodia, Myanmar | Moderate (Brittle, avoid knocks) |
| Blue Topaz | 8 | Excellent clarity; wide range of blues; very durable. | Brazil, Sri Lanka, U.S., others | High (Ideal for everyday wear) |
Choosing and Caring for Your December Gemstone
The choice among the four December birthstones depends on individual priorities: historical significance, rarity, brilliance, or durability.
- For Historical and Cultural Value: Turquoise is unmatched. Its ancient legacy and protective symbolism offer a deep connection to human history.
- For Rarity and Investment: Tanzanite is the clear choice. Its single-source origin and finite supply give it significant investment potential and a unique story.
- For Brilliance and Sparkle: Zircon is exceptional. Its fire and brilliance can rival diamonds, offering a stunning visual impact.
- For Durability and Affordability: Blue Topaz is the most practical. Its hardness makes it perfect for rings and daily wear, and its accessibility provides beautiful options within a modest budget.
Regardless of the choice, proper care is essential to preserve the gem's beauty. Always consider the gem's hardness, cleavage, and any treatments it may have undergone when cleaning and storing it. When purchasing, seek reputable sellers who provide certificates or gem reports, disclose any treatments, and offer clear return policies.
Conclusion
The December birthstones—Turquoise, Tanzanite, Zircon, and Blue Topaz—offer a remarkable diversity within a shared, wintry blue theme. From the ancient protective talisman of turquoise to the modern rarity of tanzanite, the brilliant fire of zircon, and the durable clarity of blue topaz, each gem tells a unique story of geology, history, and human meaning. This variety is a testament to the evolving nature of birthstone traditions, allowing individuals to select a stone that truly reflects their personality, values, and style. Whether chosen for its historical lore, metaphysical properties, or sheer visual beauty, any of these four gems makes a fitting and meaningful emblem for the month of December.