The tradition of assigning specific stones to each month is an ancient practice, believed to have originated in ancient civilizations such as Egypt, Greece, and Rome, where gemstones were thought to hold mystical and healing properties. In the modern era, this list was formalized. The National Association of Jewelers standardized the list of birthstones in 1912, with subsequent updates by the Jewelry Industry Council of America in 1952 and 2002, adding Zircon and Tanzanite, respectively, to the December roster. This article provides a comprehensive exploration of these four remarkable birthstones, delving into their geological formation, gemological characteristics, historical lore, and practical care.
Historical Significance and Lore
The journey of December's birthstones through history reveals a fascinating evolution from ancient talismans to modern symbols of personal expression. Turquoise, with its distinctive sky-blue to greenish hues, is the oldest of the group in terms of human use. Its name is derived from the French phrase "pierre tourques," or "Turkish stone," reflecting its introduction to Europe from the Middle East via Turkish traders. For thousands of years, it has been a stone of protection and good fortune, cherished by ancient cultures across the globe. Its association with protection is a recurring theme, making it a historically significant amulet for travelers and warriors alike.
Zircon, another of the traditional stones, is a mineral with a long and storied past. It is one of the oldest minerals on Earth, with deposits found that date back billions of years. Historically, it was believed to promote wisdom, clarity, and honor. The name "Zircon" may be derived from the Arabic word "zarkun," meaning "vermilion" or "cinnabar," or from the Persian word "zargun," meaning "gold-colored." While it is most prized today for its brilliant blue color, it has been found in a variety of hues throughout history.
The 20th century introduced two more gemstones to the December list. Tanzanite was discovered relatively recently in the mid-20th century, making it a newcomer to the world of gemstones. Its rapid rise to prominence is a testament to its exceptional beauty and rarity. It is a stone that represents transformation and new beginnings, a fitting symbolism for a gemstone that has so dramatically captured the modern imagination.
Blue Topaz, while a popular modern choice, has an ancient etymology. The name "Topaz" is believed to originate from the Greek word "Topazios," the ancient name for an island in the Red Sea. Ironically, the gemstone mined on this island was later identified as Peridot, not Topaz, but the name persisted. Blue Topaz, in its vividly saturated form, has become a staple of contemporary jewelry, valued for its brilliance and affordability.
The standardization of these stones began in 1912 with the National Association of Jewelers, which created a list that combined historical customs with gemstones that were commercially practical. This list has been updated over time to reflect new discoveries and consumer interest, with Zircon being added in 1952 and Tanzanite in 2002, solidifying the four-stone selection known today.
Geological Formation and Global Sources
Understanding the geological origins of these gemstones highlights their unique nature and rarity. Each stone forms under specific conditions, resulting in distinct chemical compositions and physical properties.
Turquoise is a secondary mineral that forms when water containing copper and aluminum seeps through pre-existing rocks. This process occurs in arid regions, where the evaporation of the mineral-rich water leaves behind deposits of turquoise in the ground. It is mined in various locations worldwide, with significant sources found in the United States (particularly Arizona and New Mexico), Iran, and Egypt. Its porous nature and characteristic matrix (the host rock remnants within the stone) are direct results of its formation process.
Zircon is a mineral belonging to the nesosilicates group and is formed in the cooling of magma. It is found in igneous and metamorphic rocks. While it is found in many places, significant commercial sources for the gem-quality blue variety include Cambodia, Sri Lanka, and Thailand. Its formation as a crystalline structure from molten rock gives it its inherent hardness and durability.
Tanzanite is the most geographically limited of all the December birthstones. It is found in only one location on Earth: a small, four-square-kilometer mining area in the Merelani Hills of Northern Tanzania. This extreme rarity contributes significantly to its high value. Tanzanite is a variety of the mineral zoisite and owes its signature violet-blue color to trace amounts of vanadium, as well as the heat treatment it undergoes either naturally (from geological events) or by man after mining.
Blue Topaz is a silicate mineral composed of aluminum and fluorine. It crystallizes from fluorine-rich vapors in the final stages of magma cooling, typically in igneous rocks like pegmatites. While natural blue topaz does occur, the vast majority of the vibrant blue topaz seen in the jewelry market is created by irradiating and heat-treating naturally colorless or pale topaz. Major sources for topaz include Sri Lanka, Brazil, Mexico, Nigeria, and the United States. The state of Texas has even designated blue topaz as its official state gem.
Gemological Properties
The four December birthstones differ significantly in their physical and chemical properties, which in turn affects their durability, appearance, and care requirements.
| Gemstone | Chemical Composition | Hardness (Mohs Scale) | Crystal System | Key Properties |
|---|---|---|---|---|
| Blue Topaz | Al₂(F,OH)₂SiO₄ | 8 | Orthorhombic | Glass-like luster, deep cleavage, often treated for color. |
| Blue Zircon | ZrSiO₄ | 6.5 - 7.5 | Tetragonal | High refractive index, high dispersion (fire). |
| Tanzanite | Ca₂Al₃(SiO₄)₃(OH) | 6.5 - 7 | Orthorhombic | Trichroic (shows three colors), pleochroic, often heat-treated. |
| Turquoise | CuAl₆(PO₄)₄(OH)₈·4H₂O | 5 - 6 | Triclinic | Opaque, porous, often contains a matrix, color ranges from sky blue to green. |
Blue Topaz is the hardest of the December stones, with a rating of 8 on the Mohs hardness scale, making it very resistant to scratching. However, it has "deep cleavage," meaning it can be split along internal planes if struck with sufficient force, so it requires care to avoid sharp impacts. Its color, ranging from pale Sky Blue to the deep inky London Blue and vibrant Swiss Blue, is almost always the result of treatment.
Blue Zircon possesses a high refractive index, giving it exceptional brilliance and sparkle, often compared to that of a diamond. It also has high dispersion, which contributes to its "fire." With a hardness of 6.5 to 7.5, it is reasonably durable but can be brittle due to its tetragonal crystal structure. The brilliant blue color of the gemstone sold today is typically achieved through heat treatment of brownish zircon crystals.
Tanzanite has a hardness of 6.5 to 7. Its most remarkable property is its strong trichroism. This means that in a single crystal, it can display three different colors depending on the viewing angle: blue, violet, and a reddish hue. Most tanzanite is heat-treated to produce the desirable blue-violet color that is commercially popular. As it is less hard than topaz or zircon, it is more susceptible to scratches and chipping.
Turquoise is the softest of the group, with a hardness of only 5 to 6. It is also opaque and porous, unlike the transparent stones of the group. Its color is determined by the amount of copper (creating blue) and iron (creating green) in its composition. The presence of the host rock, or matrix, creates the characteristic web-like patterns found in many turquoise stones. Due to its porosity, it can be damaged by chemicals, lotions, and even the oils from skin contact.
Symbolism and Metaphysical Beliefs
Across cultures and through time, each of these gemstones has been imbued with specific symbolic meanings and metaphysical beliefs.
- Turquoise is widely regarded as a stone of protection, healing, and good fortune. It was traditionally used as a talisman by ancient warriors and travelers to ward off harm and negative energy. It is also associated with tranquility, peace of mind, and spiritual grounding.
- Zircon is believed to be a stone of wisdom, clarity, and honor. It is said to help its wearer achieve a peaceful state of mind and to promote spiritual grounding. Some also associate it with attracting prosperity and abundance.
- Tanzanite, as a relatively new stone, has modern symbolic associations. It is often linked to transformation, new beginnings, and a higher consciousness. Its unique tri-colored nature is sometimes seen as a representation of the union of mind, body, and spirit.
- Blue Topaz is associated with calmness, clarity, and communication. It is believed to soothe the mind, reduce stress, and help in expressing one's thoughts and feelings clearly. It is also linked to love and affection, making it a popular gift.
Care and Cleaning
The diverse properties of December's birthstones necessitate different approaches to care and cleaning to ensure their longevity and beauty.
Blue Topaz, with its hardness of 8, is relatively durable and suitable for everyday wear. It can be safely cleaned with warm water, a small amount of mild soap, and a soft brush. However, due to its cleavage, it should be protected from hard knocks.
Blue Zircon, while hard, is brittle. It is best suited for earrings or pendants rather than rings that might receive daily impacts. Clean it with warm, soapy water and a soft brush. Avoid ultrasonic and steam cleaners, as the heat and vibrations could potentially damage the stone.
Tanzanite requires gentle handling due to its moderate hardness and potential for cleavage. It is not recommended for pieces like bracelets or rings that are worn daily. Clean it only with warm, soapy water and a soft cloth. Ultrasonic and steam cleaners are strictly forbidden.
Turquoise is the most delicate and porous of the four. It is highly susceptible to chemicals, perfumes, lotions, and even prolonged exposure to skin oils, which can cause discoloration. It should be wiped with a soft, dry cloth after wear and stored separately to avoid scratches. It should never be cleaned with ultrasonic cleaners or harsh chemicals.
Conclusion
December's birthstones offer an unparalleled selection of blue gemstones, each with a distinct identity. From the ancient, protective Turquoise to the brilliantly sparkling Blue Zircon, the rare and transformative Tanzanite, and the vibrant, durable Blue Topaz, there is a stone to suit every preference and style. This rich variety is a direct result of both geological chance and a historical evolution of birthstone traditions, which have expanded to provide more options for those born in this festive month. Understanding the unique origins, properties, and care requirements of each gemstone allows enthusiasts and buyers to appreciate not only their aesthetic beauty but also their enduring scientific and cultural significance.