December is unique in the world of birthstones, offering not one, but four distinct blue gemstones: turquoise, zircon, tanzanite, and blue topaz. This abundance sets it apart from every other month, providing a diverse palette of icy blues, deep violets, and sky-like hues that perfectly mirror the winter season. The selection of these four stones is a modern evolution, blending ancient traditions with contemporary gemological discoveries and commercial considerations. While turquoise is one of the oldest known gemstones, cherished for millennia, tanzanite is a relative newcomer, discovered in the 20th century. Blue topaz, while historically known, gained prominence as a popular birthstone option more recently. Zircon, one of the oldest minerals on Earth, completes the quartet. Each stone carries its own unique history, geological origin, physical properties, and cultural symbolism, offering a rich tapestry of choices for those born in the final month of the year. This article will explore the history, formation, gemological characteristics, and care requirements of these four remarkable December birthstones, drawing exclusively from the provided source materials to provide an authoritative guide for gemstone enthusiasts, jewelry buyers, and students of gemology.
Historical Evolution and Modern Standardization
The concept of birthstones has deep roots in historical and religious traditions, often linked to the twelve stones of Aaron's breastplate in the Bible or the foundation stones of the New Jerusalem. Over centuries, these associations evolved into a monthly system. The modern list of birthstones, however, was formalized in the early 20th century. In 1912, the National Association of Jewelers (now the Jewelers of America) standardized an unofficial American list, combining historical customs with gemstones that were practical for jewelry companies to sell and market. This list has been updated several times to reflect new discoveries and market trends.
December's list has seen particular growth. Initially, turquoise and zircon were the primary stones associated with the month. In 1952, the Jewelry Industry Council of America updated the list, formally adding zircon to December’s options. The most recent major addition occurred in 2002, when tanzanite was added to the list. Blue topaz, while not part of the original or first updated lists, has become widely recognized as a fourth December birthstone, especially valued for its durability and crisp blue color. The reason for December having four birthstones is not definitively known, but some sources suggest it was to provide more affordable options as the gemstone market evolved. This evolution demonstrates how birthstone lists can change with new gemstone discoveries and commercial offerings, ensuring the tradition remains relevant and diverse.
Geological Formation and Global Sources
Each of the four December birthstones forms under distinct geological conditions, leading to their unique appearances and locations.
Turquoise is a secondary mineral that forms in arid regions where acidic, copper-rich groundwater percolates through rocks containing aluminum and phosphorus. The most significant sources include the southwestern United States (notably Arizona and New Mexico), Iran, Egypt, China, Mexico, and parts of Central Asia and Africa. These regions provide the specific copper-rich geological formations and weather conditions necessary for its formation. Turquoise is often recognized by its distinctive matrix—the host rock from which it was formed—which can create intricate, spiderweb-like patterns within the stone.
Zircon is a zirconium silicate mineral and is one of the oldest minerals on Earth, with some crystals dating back billions of years. It forms in a variety of rock types, including igneous and metamorphic rocks. The primary sources for gem-quality zircon include Sri Lanka, Cambodia, and Australia. Colorless zircon was historically mistaken for diamond due to its brilliance and fire, but blue zircon, often created through heat treatment of brown zircon, is the variety most associated with December.
Tanzanite is the rarest of the four December birthstones, found exclusively in a single, small mining area in the Merelani Hills of Northern Tanzania. This geographic limitation makes it exceptionally rare and valuable. Its formation is linked to a unique geological event where heat and pressure transformed zoisite into the blue-violet tanzanite we know today. The specific conditions required for its formation have only occurred in this one location on Earth.
Blue Topaz is a silicate mineral of the aluminum and fluorine group. While natural blue topaz exists, the vibrant, deep blues commonly seen in jewelry are almost always the result of irradiation and heat treatment of colorless or pale topaz. Topaz is mined in various locations worldwide, including Sri Lanka, Brazil, Mexico, Nigeria, and the United States. The U.S. state of Texas has even designated blue topaz as its official state gem.
Gemological Properties: A Comparative Analysis
Understanding the physical and chemical properties of these gemstones is crucial for appreciating their value, durability, and care requirements. The table below summarizes key gemological data for each December birthstone, based on the provided sources.
| Property | Tanzanite | Turquoise | Zircon | Blue Topaz |
|---|---|---|---|---|
| Natural Color | Blue to violet | Sky blue to greenish | Blue (often heat-treated) | Pale blue to dark blue (often treated) |
| Common Treatments | Heat treatment is common to enhance color. | Stabilization (impregnation) is common to improve durability and color. | Heat treatment is common to produce blue from brown zircon. | Irradiation and heat treatment are standard to produce blue color. |
| Mohs Hardness | 6 to 7 | 5 to 6 | 6.5 to 7.5 | 8 |
| Best For | Occasional rings, earrings, pendants | Earrings, pendants, beads | Earrings, pendants, and protected rings | Daily wear rings, all jewelry |
| Sensitivity | Prone to chipping along cleavage. | Sensitive to chemicals, moisture, and impacts. | Brittle at edges; can be chipped with sharp knocks. | Sensitive to sharp impacts, though durable. |
| Care Needs | Gentle cleaning only with warm, soapy water. Avoid ultrasonic and steam cleaners. | Very gentle cleaning; avoid all chemicals and prolonged moisture. | Avoid steam and ultrasonic cleaners. Clean with warm, soapy water. | Mild care; avoid sharp hits. Can be cleaned with standard methods. |
Turquoise: The Ancient Talisman
With a Mohs hardness of approximately 5 to 6, turquoise is relatively soft compared to the other December stones, making it susceptible to scratching and damage. Its chemical composition is a hydrated phosphate of copper and aluminum, which gives it its characteristic blue to greenish-blue color. The presence of iron can shift the color toward green, while the copper content determines the blue intensity. Because natural turquoise is often porous, it is commonly treated with wax or resin (stabilization) to fill pores, improve luster, and enhance durability. This process is standard in the industry and does not diminish the stone's value if properly disclosed. The stone's sensitivity to chemicals, heat, and moisture means it requires careful handling and should not be exposed to perfumes, lotions, or prolonged water immersion.
Zircon: The Diamond Imitator
Zircon, with a hardness of 6.5 to 7.5 on the Mohs scale, is significantly harder than turquoise and tanzanite, though not as hard as blue topaz. It is a zirconium silicate (ZrSiO₄) and is known for its high refractive index and strong dispersion (fire), which is why it was often confused with diamond in historical settings. The blue variety typically starts as brown zircon, which is heated to high temperatures to produce a stable blue color. While durable, zircon has perfect cleavage in two directions, meaning it can be chipped or fractured if struck with a sharp blow, especially at its edges. It is therefore recommended for earrings, pendants, and rings with protective settings. Cleaning should be done with warm, soapy water, avoiding ultrasonic and steam cleaners which could cause damage.
Tanzanite: The Rare Violet-Blue
Tanzanite ranks 6 to 7 on the Mohs hardness scale, placing it in a moderate durability category. It is a variety of the mineral zoisite, and its distinctive blue-violet color is the result of heat treatment applied to brownish zoisite crystals after mining. This treatment is permanent and does not affect the stone's durability. However, tanzanite is known to be brittle and can chip along its natural cleavage planes if subjected to sharp impacts. Its exclusive origin in Tanzania adds to its rarity and value. For jewelry, tanzanite is best set in earrings, pendants, or occasional-wear rings with protective settings. Cleaning should be done gently with warm, soapy water, and ultrasonic and steam cleaners should never be used, as they can cause internal fractures or damage.
Blue Topaz: The Durable Winter Blue
Blue topaz is the hardest of the four December birthstones, with a Mohs hardness of 8, making it highly durable and suitable for everyday wear, including rings. It is a silicate mineral of aluminum and fluorine. The vivid blue colors (such as Swiss Blue or London Blue) are achieved through irradiation of colorless topaz, followed by heat treatment to stabilize the color. This process is permanent and does not create additional durability concerns. While hard, blue topaz can still be chipped by sharp impacts, so care should be taken with active wear. Its durability and affordability have made it a popular choice for modern jewelry. Cleaning is straightforward; mild soap and water are sufficient, and it can tolerate standard jewelry cleaning methods.
Symbolism and Cultural Significance
Each December birthstone carries a rich legacy of symbolism and metaphysical beliefs, reflecting the cultures and eras that have cherished them.
Turquoise is one of the oldest gemstones in human history, cherished by royalty such as Ancient Egyptian pharaohs and King Tutankhamun. For millennia, it has been regarded as a protective talisman, believed to ward off negative energy, falls, and harm. It symbolizes wisdom, tranquility, friendship, and good fortune. In many cultures, it is seen as a steadying force, providing grounding and a sense of calm. Its distinctive color, ranging from sky blue to greenish hues, is associated with the winter sky and is considered perfect for the cold-weather season.
Zircon has a long history of metaphysical associations. During the Middle Ages, it was believed to induce deep sleep and repel evil spirits. In Hindu tradition, zircon is one of the nine gems (navaratna) in the navaratna, and when worn together, these gems are said to protect the wearer and bring wealth, wisdom, and good health. Victorian-era enthusiasts particularly favored blue zircon. The stone is associated with clarity, wisdom, and a sense of balance, believed to sharpen focus and enhance mental clarity.
Tanzanite, as a modern addition to the birthstone list, carries symbolism linked to transformation and new beginnings. Its unique blue-violet color, which shifts depending on the light, is said to reflect the feeling of stepping into a new chapter with clarity and curiosity. It represents growth, change, and the opening of new doors. Given its recent discovery and exclusive origin, tanzanite's lore is more contemporary but deeply tied to its rarity and the sense of wonder it inspires.
Blue Topaz, while its historical lore is less documented in the provided sources compared to the others, is valued for its crisp, icy blue color that mirrors winter skies. Its durability makes it a practical symbol of lasting strength and clarity. As a state gem of Texas, it also holds regional significance. In broader metaphysical beliefs, topaz is often associated with clarity of thought and communication, aligning with its clear, brilliant appearance.
Care and Maintenance Guidelines
Proper care is essential to preserve the beauty and longevity of these gemstones, and their differing physical properties dictate specific maintenance routines.
Turquoise: Due to its softness (5-6 Mohs) and porosity, turquoise requires the most careful handling. It should be cleaned only with a soft, dry cloth. Avoid all chemicals, including perfumes, lotions, and household cleaners, as they can damage the stone and its stabilization treatment. Prolonged exposure to water or moisture should be avoided, as it can cause the stone to crack or the matrix to weaken. Store turquoise jewelry separately to prevent scratches from harder gems.
Zircon: With a hardness of 6.5-7.5 and cleavage, zircon is relatively durable but can be brittle. Clean it with warm, soapy water and a soft brush. Avoid ultrasonic and steam cleaners, as the vibrations and heat can cause fractures along cleavage planes. It is best stored in a fabric-lined box away from other jewelry to prevent chipping.
Tanzanite: This gemstone's moderate hardness (6-7) and cleavage make it prone to chipping. It should be cleaned gently with warm, soapy water and a soft brush. Never use ultrasonic cleaners or steam cleaners, as they can cause severe damage. Due to its brittleness, tanzanite is best set in protective jewelry like earrings or pendants, or in rings with secure, low-profile settings that guard against knocks.
Blue Topaz: As the hardest of the group (8 Mohs), blue topaz is the most resilient for daily wear. It can be cleaned with standard jewelry cleaning methods, including mild soapy water and a soft brush. While durable, it is still susceptible to chipping from sharp impacts, so it should be removed during vigorous activities. Avoid extreme temperature changes, which could potentially damage the stone.
Conclusion
December’s four birthstones—turquoise, zircon, tanzanite, and blue topaz—offer an unparalleled variety of blue gemstones, each with a distinct identity. Turquoise stands as an ancient protector, valued for its historical significance and stabilizing energy. Zircon, one of Earth's oldest minerals, provides brilliant fire and a connection to centuries of lore. Tanzanite, the rare and exclusive gem from Tanzania, captivates with its shifting violet-blue hues and symbolism of transformation. Blue topaz, with its exceptional hardness and crisp, icy brilliance, serves as a durable and accessible modern favorite. Together, they reflect the full spectrum of winter’s palette, from the soft sky of a clear day to the deep twilight of a long night. Understanding their unique histories, geological origins, gemological properties, and care requirements allows enthusiasts and buyers to make informed choices, selecting a gemstone that not only marks a December birthday but also resonates with personal style and appreciation for the natural world’s artistry.