December is a month rich in tradition, celebration, and natural beauty. As the final month of the year, it marks the turning of the seasons and is associated with the winter solstice, the holidays, and the renewal of life that follows the long, cold nights. It is also a month symbolically linked to the power of gemstones. December is one of only two months that have more than one official birthstone—specifically, tanzanite, turquoise, and zircon, with blue topaz also occasionally included in the list. Each of these gems carries a unique combination of historical significance, gemological properties, and cultural symbolism, making them not only beautiful choices for jewelry but also meaningful symbols for those born during this time.
This article delves into the origins, characteristics, and significance of the December birthstones, offering a comprehensive guide for gemstone enthusiasts, jewelry buyers, and students of gemology. From their geological formation to their spiritual associations, we will explore the multifaceted nature of these gems and what makes them treasured in both ancient and modern times.
History and Lore
The concept of birthstones is an ancient tradition with roots in religious and cultural texts. One of the earliest references to gemstones assigned to months is found in the Biblical Book of Exodus, where the High Priest's breastplate was adorned with 12 stones, each representing a tribe of Israel. These early stones did not map directly to the modern calendar months, but they laid the foundation for the later association of gemstones with specific times of the year.
The modern birthstone system, however, evolved in the 19th and 20th centuries, with various organizations and jewelers contributing to its standardization. Tiffany & Co. played a significant role in the 1870s by promoting turquoise as the December birthstone. Later, in 1912, the National Association of Jewellers (now the Jewellers of America) recognized turquoise as the primary December birthstone and lapis lazuli as an alternative.
In 1952, the Jewelry Industry Council of America added zircon to the list of December birthstones, and in 2002, tanzanite was officially recognized as the third December birthstone in the United States. This evolution reflects the dynamic nature of the birthstone tradition, which continues to adapt to new discoveries and cultural influences.
December’s three primary birthstones—tanzanite, turquoise, and zircon—each bring their own distinct history and symbolism to the month. Turquoise, for example, has been revered for thousands of years, particularly in ancient Egypt, Persia, and the Americas, where it was considered a sacred stone. Zircon, especially in its blue variety, has been used in jewelry since antiquity and was once known as “hyacinth.” Tanzanite, by contrast, is a modern discovery, first found in Tanzania in 1967, and is celebrated for its rarity and vibrant color.
Geological Formation and Sources
Tanzanite
Tanzanite is a relatively new gemstone in the world of jewelry, having been discovered in 1967 in Merelani Hills, Tanzania, the only place in the world where it is found. It is a trigonal mineral, a variety of the cushion stone zoisite, which is typically brown in its natural state. The blue to violet coloration of tanzanite is the result of heat treatment, which transforms the brown zoisite into the vibrant gemstone we recognize today. This treatment is stable and does not affect the gem's durability.
Tanzanite is rated between 6 and 7 on the Mohs scale of hardness, making it relatively durable for a colored gemstone, though not as hard as diamonds or sapphires. Because of its trigonal crystal system, it has cleavage, which means it can be prone to chipping or cracking, especially under high temperatures or sudden temperature changes. It is also susceptible to damage from hydrochloric and hydrofluoric acids, so it requires careful cleaning and storage.
Turquoise
Turquoise is a phosphate mineral composed of copper and aluminum, with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It forms in arid regions, typically in limestone deposits, where it is altered by groundwater and metallic elements. The bluish-green color of turquoise is due to the presence of copper, while the yellow or brown hues come from iron impurities.
Historically, turquoise has been mined in Persia (modern-day Iran), Egypt, and the American Southwest. Some of the most prized turquoise comes from the mines of Nevada and New Mexico in the United States, as well as from China and Pakistan. In Egypt, turquoise was used in jewelry and amulets as early as 4000 BCE, and it was often associated with protection and divine favor.
Turquoise is a relatively soft gemstone, rated at 5 to 6 on the Mohs scale, and is porous, which makes it susceptible to damage from heat, chemicals, and prolonged exposure to light. It is also prone to cracking and crumbling if it becomes dry, so it requires moisture and gentle handling.
Zircon
Zircon is a zirconium silicate with the chemical formula ZrSiO₄, and it occurs in both natural and synthetic forms. It is a metamorphic mineral, typically found in granite and metamorphosed sedimentary rocks. The blue color of zircon is the result of heat treatment, which removes hydrogen from the crystal structure, changing the color from brown to blue.
Zircon is rated at 6 to 7.5 on the Mohs scale, making it more durable than turquoise but slightly less hard than tanzanite. It is known for its high refractive index and dispersion, which gives it a sparkling appearance similar to diamond. Zircon is also thermally stable, making it resistant to heat and light.
The most significant sources of blue zircon are Vietnam, Cambodia, and Myanmar, though zircon is also found in Australia, Thailand, and the United States. It has been used in jewelry for centuries, and in ancient times, it was often referred to as hyacinth due to its similar appearance and fiery color.
Gemological Properties
Tanzanite
| Property | Value |
|---|---|
| Chemical Formula | Ca₂Al₃(SiO₄)(OH)₂ |
| Crystal System | Trigonal |
| Color | Blue to violet |
| Hardness (Mohs) | 6–7 |
| Specific Gravity | 3.1–3.4 |
| Refractive Index | 1.694–1.700 |
| Transparency | Transparent to translucent |
| Cleavage | Perfect in one direction |
| Luster | Vitreous to greasy |
| Origin | Tanzania |
| Treatment | Heat-treated from brown zoisite |
Tanzanite is known for its trichroism, meaning it displays three different colors when viewed from different angles. This effect enhances its visual appeal and makes it a popular choice for statement jewelry. Its heat treatment is a standard industry practice and does not affect the gem's stability.
Turquoise
| Property | Value |
|---|---|
| Chemical Formula | CuAl₆(PO₄)₄(OH)₈·4H₂O |
| Crystal System | Trigonal |
| Color | Blue, green, yellow |
| Hardness (Mohs) | 5–6 |
| Specific Gravity | 2.7–2.9 |
| Refractive Index | 1.61–1.65 |
| Transparency | Opaque to translucent |
| Cleavage | None |
| Luster | Waxy to greasy |
| Origin | Persia, Egypt, Americas, China, Pakistan |
| Treatment | Stabilization with resins, dyes |
Turquoise is a porous and soft gemstone, which means it requires careful handling and storage. It is often stabilized with resin or dye to enhance its color and durability. This treatment is permanent, and the gem is safe for jewelry when properly cared for.
Zircon
| Property | Value |
|---|---|
| Chemical Formula | ZrSiO₄ |
| Crystal System | Tetragonal |
| Color | Blue, brown, yellow |
| Hardness (Mohs) | 6–7.5 |
| Specific Gravity | 4.0–4.7 |
| Refractive Index | 1.92–2.00 |
| Transparency | Transparent to translucent |
| Cleavage | None |
| Luster | Vitreous |
| Origin | Vietnam, Cambodia, Myanmar, Australia, Thailand |
| Treatment | Heat-treated to blue color |
Zircon is known for its high refractive index and dispersion, giving it a sparkling appearance that is often compared to diamond. It is also thermally stable, making it suitable for everyday wear. The blue variety is the most popular and widely recognized as a December birthstone.
Symbolism and Metaphysical Beliefs
The December birthstones are not only admired for their beauty and rarity but also for their symbolic and spiritual significance. These gems have been used for healing, protection, and personal transformation across various cultures and eras.
Tanzanite
Tanzanite is often associated with spiritual growth, emotional healing, and communication. It is believed to activate the throat, third-eye, and crown chakras, helping the wearer to express themselves clearly and connect with higher dimensions. Some people use tanzanite for dream work, as it is said to enhance intuition and psychic abilities.
In terms of emotional support, tanzanite is known for its calming energy, which helps to soothe stress and anxiety. It is also a stone of transformation, encouraging self-discovery and personal growth.
Turquoise
Turquoise has a long history of being used as a stone of protection and good fortune. In ancient Egypt, it was used in jewelry and amulets to ward off evil spirits and bring prosperity. In Native American cultures, it was considered a sacred stone, often used in ceremonies and rituals to promote healing and harmony.
Turquoise is also associated with self-expression and truth-telling, making it a valuable gemstone for those seeking clarity and honesty. It is believed to enhance communication skills and encourage openness and honesty in relationships.
Zircon
Zircon, especially in its blue form, is known for its joyful and uplifting energy. It is associated with emotional balance and happiness, and is often used to clear negative emotions and promote positivity. Zircon is also believed to enhance intuition and creativity, making it a valuable stone for artists, writers, and healers.
In ancient times, zircon was known as hyacinth, and was associated with divine fire and spiritual power. It was used in jewelry and amulets to protect the wearer and enhance their spiritual connection.
Care and Cleaning
Proper care and cleaning are essential to maintaining the beauty and longevity of December birthstones, especially since some of them are relatively soft or porous.
Tanzanite
Tanzanite should be cleaned with warm, soapy water and a soft cloth or brush. Ultrasonic and steam cleaners are not recommended, as they can damage the gem or cause it to crack. Tanzanite should also be stored separately from harder gemstones to avoid scratching.
Because of its trigonal crystal system, tanzanite is susceptible to thermal shock, so it should be avoided from exposure to extreme temperature changes. It is also sensitive to acids, so it should be kept away from household cleaners and chemicals.
Turquoise
Turquoise is a porous gemstone and should be cleaned gently with warm, soapy water and a soft cloth or brush. Ultrasonic and steam cleaners are not recommended, as they can damage the stone or dry it out, causing cracking or crumbling.
Turquoise should be stored in a **cool, moist place, as it can dry out and lose its color over time. It should also be kept away from direct sunlight and strong artificial light, which can fading its color.
Zircon
Zircon is more durable than tanzanite and turquoise and can be cleaned with warm, soapy water, a soft cloth or brush, and ultrasonic cleaners. It is thermally stable, so it can withstand heat and light without changing color or losing its luster.
Zircon should be stored separately from harder gemstones to avoid scratching. It is also resistant to most chemicals, making it easier to care for than some of the other December birthstones.
Conclusion
The December birthstones—tanzanite, turquoise, and zircon—are more than just beautiful gems; they are symbols of protection, transformation, and emotional balance. Each of these stones carries a rich history, unique gemological properties, and profound spiritual significance, making them treasured gifts and meaningful jewelry choices.
Whether you are shopping for a December-born loved one, exploring the history and meaning of gemstones, or simply appreciating the beauty of these rare and vibrant stones, the December birthstones offer something for everyone. From the velvety blue of tanzanite to the timeless elegance of turquoise and the sparkling brilliance of zircon, these gems are true treasures of the winter months.