The month of December is uniquely associated with three distinct and captivating birthstones: turquoise, tanzanite, and zircon. Each of these gems offers a remarkable spectrum of color, from the sky-blue of classic turquoise to the vibrant violet-blue of tanzanite and the fiery brilliance of zircon. While their origins and properties differ dramatically, they are united by their celebrated place in modern jewelry, particularly as personalized birthstone necklaces. These stones serve as powerful symbols of identity, personal expression, and thoughtful gifting, allowing wearers to connect with the month of their birth in a tangible and elegant form.
The journey of these stones from the earth to a necklace pendant involves a rich interplay of geology, history, and contemporary craftsmanship. Understanding their unique characteristics—from the ancient lore of turquoise to the recent discovery of tanzanite—provides a deeper appreciation for the jewelry they adorn. This article will explore the history, geological origins, gemological properties, and cultural significance of December's three birthstones, offering a comprehensive guide for gemstone enthusiasts, jewelry buyers, and students of gemology.
Historical Significance and Modern Birthstone Assignments
The tradition of associating specific gemstones with birth months has evolved over centuries, with its roots in the breastplate of the High Priest of Ancient Israel, which featured twelve stones representing the twelve tribes. The modern list of birthstones was standardized in 1912 by the American National Association of Jewelers (now Jewelers of America), with subsequent updates. December's trio—turquoise, tanzanite, and zircon—reflects this evolution, blending ancient tradition with modern discovery.
Turquoise is one of the oldest known gemstones, prized by ancient civilizations including the Egyptians, Persians, and Native Americans. Its name derives from the French "pierre turquoise," meaning "Turkish stone," as it was brought to Europe from Turkey. Historically, it was believed to be a powerful protective amulet, warding off evil and bringing good fortune. Its status as a December birthstone is deeply entrenched in Western tradition.
Zircon has a history nearly as ancient as turquoise. For centuries, it was confused with cubic zirconia, a synthetic material, which has sometimes overshadowed its natural beauty. However, zircon is one of the oldest minerals on Earth, with deposits dating back billions of years. It has been used in jewelry since the Middle Ages and was historically believed to promote honor, purity, and wisdom.
Tanzanite is the newest addition to the birthstone family. Discovered in Tanzania in the late 1960s, its vibrant violet-blue hue captivated the gemological world. In 2002, the American Gem Trade Association (AGTA) officially added tanzanite as an alternate birthstone for December, recognizing its growing popularity and unique color.
Geological Formation and Mining Locations
Each of December's birthstones forms under distinct geological conditions, resulting in unique mining locations and availability.
Turquoise is a secondary mineral formed when water containing copper and aluminum seeps through pre-existing rocks, such as volcanic ash. The process can take millions of years. The finest quality turquoise is often found in arid regions. While historically mined in Persia (modern-day Iran), today's most significant sources include the United States (particularly Arizona and New Mexico), China, and Tibet. The gem is frequently found in nodules or veins within a host rock, which is often removed during cutting, leaving the stone as a cabochon.
Zircon is a mineral that crystallizes from magma as it cools deep within the Earth's crust. It is a common byproduct of the mining industry for other minerals like tin and is often found in alluvial deposits (sediments carried by water). Major sources include Cambodia, Sri Lanka, Australia, and the United States. Colorless zircon was particularly popular in the Middle Ages and is sometimes used as a diamond simulant due to its high refractive index and brilliance.
Tanzanite forms through a unique geological process involving the metamorphism of minerals in the Merelani Hills of Tanzania, the only known commercial source of this gem. The process involves the heating of zoisite, which, in the presence of trace elements like vanadium, transforms into tanzanite's distinctive blue-violet color. This limited geographic source makes tanzanite exceptionally rare; some geologists estimate that the deposits may be exhausted within a few decades, adding to its value and allure.
Gemological Properties
Understanding the physical and chemical properties of these gems is crucial for identification, valuation, and proper care. The following table summarizes key gemological characteristics based on established standards.
| Gemstone | Chemical Composition | Crystal System | Hardness (Mohs Scale) | Typical Treatments | Notable Properties |
|---|---|---|---|---|---|
| Turquoise | Hydrated copper aluminum phosphate | Triclinic | 5 - 6 | Stabilization (dyeing, impregnation with resin) | Often porous; color can fade with prolonged light/heat exposure. |
| Tanzanite | Calcium aluminum hydroxyl silicate (Zoisite) | Orthorhombic | 6.5 - 7 | Heat treatment (standard for all commercial tanzanite) | Strong trichroism (shows blue, violet, and reddish tones). |
| Zircon | Zirconium silicate (ZrSiO₄) | Tetragonal | 6.5 - 7.5 | Heat treatment (for colorless and blue varieties) | High refractive index; excellent brilliance; can be radioactive (low levels). |
Turquoise is relatively soft compared to other gemstones, with a hardness of 5 to 6 on the Mohs scale. It is often porous, which leads to common treatments. "Stabilized" turquoise is impregnated with a clear resin to enhance durability and color consistency. Natural, untreated turquoise is highly valued but requires more careful handling. Its color ranges from sky blue to greenish-blue, influenced by the amount of copper (blue) and iron (green) in its composition.
Tanzanite has a hardness of 6.5 to 7, making it suitable for jewelry but more susceptible to scratches than harder stones like sapphire. Its most defining characteristic is strong trichroism, where the gem can display three different colors—blue, violet, and reddish-brown—depending on the crystal orientation. Virtually all commercial tanzanite is heat-treated to achieve the desired vivid blue-violet color, a process that is considered permanent and stable.
Zircon is the hardest of the three, with a hardness of 6.5 to 7.5, and has a high refractive index, giving it exceptional brilliance and fire, often surpassing that of diamond. It is important to note that some zircon crystals contain trace amounts of uranium and thorium, which can cause natural radioactivity. However, the levels are generally very low and not a health concern for jewelry wearers. Zircon comes in a variety of colors, with blue (often heat-treated from brownish zircon) and colorless being the most popular for jewelry.
Symbolism and Metaphysical Beliefs
Beyond their physical beauty, these stones are imbued with centuries of symbolic meaning and metaphysical beliefs, which continue to resonate with many wearers today.
Turquoise has long been regarded as a stone of protection, healing, and good fortune. In many cultures, it was believed to break when its owner was in danger, serving as a warning. Native American tribes considered it a sacred stone, representing the sky and water, and used it in ceremonies and as a protective amulet. It is also associated with emotional balance, clarity, and creativity.
Zircon has been historically linked to honor, purity, and wisdom. In the Middle Ages, it was thought to promote sound sleep, ward off evil spirits, and bring prosperity. Its brilliance was associated with light and truth. Today, it is sometimes believed to enhance self-confidence and spiritual grounding.
Tanzanite, as a modern gem, has developed its own set of metaphysical attributes. It is often called the "stone of transformation," believed to facilitate a higher consciousness and spiritual awakening. Its unique color is associated with the crown and third eye chakras, promoting intuition and clear communication. Some believe it can help overcome grief and trauma, making it a stone of emotional healing.
Care and Cleaning
Proper care is essential to maintain the beauty and longevity of birthstone jewelry, and the required methods vary significantly among these three gems due to their differing properties.
Turquoise Care: Due to its porosity and relative softness, turquoise requires gentle handling. Avoid exposure to chemicals, including perfumes, lotions, and household cleaners, which can damage or discolor the stone. Clean it only with a soft, dry cloth. Do not use ultrasonic cleaners or steam, as the vibrations and heat can cause cracking or discoloration. It is best to remove turquoise jewelry before swimming or showering.
Tanzanite Care: With a hardness of 6.5 to 7, tanzanite is moderately durable but can be scratched by harder materials. It should be stored separately from other jewelry to avoid contact. Clean tanzanite with warm water, a mild soap, and a soft brush. Avoid sudden temperature changes and prolonged exposure to strong light, as heat can potentially damage the stone (though standard heat treatment is stable). Ultrasonic cleaners are not recommended.
Zircon Care: Zircon's hardness makes it relatively durable for daily wear, but it can be brittle and prone to chipping if struck hard. It is sensitive to heat and can be damaged by rapid temperature changes. Clean zircon with warm, soapy water and a soft brush. Avoid ultrasonic cleaners, as the vibrations can cause existing fractures to worsen. Store it carefully to prevent scratches from harder gems like diamonds or sapphires.
The Birthstone Necklace: A Personal Statement
The provided sources highlight the significance of birthstone necklaces as a means of personal expression and thoughtful gifting. These necklaces are often crafted from precious metals like recycled gold, rose gold, or sterling silver, providing a durable and elegant setting for the gemstone. The ability to customize these pieces—by adding names, initials, or selecting specific designs—transforms a simple pendant into a unique signature piece. For December-born individuals, a necklace featuring turquoise, tanzanite, or zircon becomes a tangible connection to their birth month, carrying both aesthetic beauty and personal significance.
As a gift, a birthstone necklace carries a layer of meaning that generic jewelry cannot match. It demonstrates a thoughtful consideration of the recipient's identity and birth month, making it an ideal present for birthdays, holidays, or other milestones. The versatility in style—from minimalist solitaires to intricate, stacked designs—ensures there is a perfect piece for every taste and occasion.
Conclusion
The birthstones of December—turquoise, tanzanite, and zircon—offer a remarkable diversity in color, origin, and history. From the ancient, protective talisman of turquoise to the recently discovered, transformative energy of tanzanite and the brilliant, timeless fire of zircon, each gem provides a unique way to celebrate the month of December. Their journey from the earth, shaped by millennia of geological processes, to the skilled hands of a jeweler, results in objects of enduring beauty and personal significance. Whether chosen for its historical lore, metaphysical properties, or simply its captivating hue, a December birthstone necklace is more than an accessory; it is a deeply personal emblem of identity, a piece of the earth's artistry worn close to the heart.