December, the final month of the year, is uniquely marked by having not one, but three official birthstones: turquoise, tanzanite, and zircon. This multiplicity of gemstones reflects the evolving nature of birthstone traditions and the rich tapestry of cultural, geological, and symbolic significance that these stones carry. Each of these gemstones has its own history, properties, and lore, making them not only beautiful adornments but also meaningful symbols for those born in December.
This article delves into the detailed characteristics of each of these December birthstones, exploring their historical and cultural significance, geological formation, gemological properties, and their symbolic and metaphysical associations. The information is drawn from authoritative and historical sources, providing a well-rounded and accurate overview for gemstone enthusiasts, jewelry buyers, and students of gemology.
Historical and Cultural Significance of December Birthstones
The concept of birthstones is ancient, with roots in biblical and mythological traditions. The earliest known birthstone list appears in the Breastplate of Aaron, described in the Book of Exodus, which lists twelve gemstones, each corresponding to a tribe of Israel. However, the assignment of these stones to modern months is a much later development, influenced by medieval and Renaissance-era adaptations.
The Evolution of December Birthstones
December has had a particularly dynamic history when it comes to its birthstone designation. According to historical records, the earliest December birthstone was ruby, as listed in biblical interpretations. However, over time, other stones were added to the list to reflect both cultural preferences and gemological availability.
A timeline of December’s birthstones is as follows:
- 1870 – Turquoise was designated as the December birthstone by Tiffany & Co. in their “Gregorian Birthstone Poems” pamphlet.
- 1912 – The National Association of Jewellers (now the Jewelers of America) listed turquoise as the primary December birthstone and lapis lazuli as an alternative.
- 1952 – The Jewelry Industry Council of America added zircon to the December birthstone list.
- 2002 – The GIA (Gemological Institute of America) officially added tanzanite, making December the only month with three official birthstones.
This evolution reflects not only changes in gemological understanding but also the influence of jewelry industry marketing and cultural trends.
The Reason for Multiple Birthstones
The inclusion of multiple stones for some months, including December, was partly driven by the desire to offer affordable alternatives to rarer and more expensive gems. For example, turquoise has long been a popular and accessible stone, while tanzanite, discovered in 1967, was introduced to expand the December birthstone options.
The variety of December birthstones also allows individuals to choose a gem that best suits their personal style, budget, and symbolic preference. Each stone carries unique colors, meanings, and cultural associations, offering a diverse palette of choices.
Geological Formation and Sources of December Birthstones
Understanding the geological origins of a gemstone provides insight into its rarity, availability, and unique properties. Each of December’s birthstones forms under different conditions and is found in distinct geographical locations.
Turquoise
Turquoise is a phosphate mineral composed of copper and aluminum. Its formation is closely tied to weathering processes in arid environments. The stone typically forms when acidic groundwater interacts with copper-rich rocks, dissolving the copper and depositing it in cavities where it combines with aluminum and phosphorus to form turquoise.
- Color: Turquoise ranges in color from sky blue to greenish blue, depending on the presence of iron and aluminum.
- Hardness: It has a Mohs hardness of 5–6, making it relatively soft and prone to scratching and fracturing.
- Luster: It has a waxy to vitreous luster and is often porous, requiring stabilization for use in jewelry.
Major sources of turquoise include:
- United States – Especially Arizona, New Mexico, and Nevada, where turquoise has been mined for centuries.
- China – Known for producing greenish turquoise.
- Iran (Persia) – Historical source of some of the finest turquoise, often called Persian turquoise.
- Egypt – Used by ancient Egyptians for jewelry and amulets.
Turquoise is also hydrophilic, meaning it can absorb water and oils, which can affect its color and integrity over time. This is why it is often dyed or stabilized before being used in jewelry.
Tanzanite
Tanzanite is a trigonal crystal form of zoisite, a mineral that contains vanadium, which gives it its deep blue to violet color. Discovered in 1967 in Tanzania, tanzanite was first marketed as a December birthstone in 2002 by the GIA.
- Color: Tanzanite is known for its trichroism, meaning it can display three different colors (blue, violet, and brown) depending on the angle of light.
- Hardness: It has a Mohs hardness of 6–7, which is relatively durable for a colored gemstone.
- Luster: Tanzanite has a glassy (vitreous) luster and is often heat-treated to enhance its color.
Tanzanite is exclusive to Tanzania, where it is found in metamorphic rock formations in the Merelani Hills. The stone is highly valued for its vibrant color and rarity, and its limited geographic origin makes it a unique and collectible gemstone.
Zircon
Zircon is a zirconium silicate that occurs in various colors, including blue, yellow, red, green, and brown. The blue zircon used as a December birthstone is the most popular and is typically heat-treated to achieve its bright blue color.
- Color: Blue zircon is the most common variety used for jewelry, but zircons can occur in nearly every color of the rainbow.
- Hardness: Zircon has a Mohs hardness of 6–7.5, depending on the variety.
- Luster: It has a glassy to adamantine (diamond-like) luster and is known for its high refractive index, which gives it a sparkling appearance.
Zircon is found in igneous and metamorphic rocks around the world, with notable sources including:
- Burma (Myanmar)
- India
- Sri Lanka
- Australia
- Brazil
Zircon is also known for its radioactive properties, as some varieties contain trace amounts of uranium and thorium. However, this is not a concern for jewelry use, as the radioactivity is generally low and not harmful.
Gemological Properties of December Birthstones
Each of December’s birthstones has distinct physical and optical properties that define its beauty and durability. Below is a detailed comparison of their gemological features:
| Gemstone | Color | Mohs Hardness | Chemical Formula | Refractive Index | Luster | Transparency | Primary Sources |
|---|---|---|---|---|---|---|---|
| Turquoise | Blue to greenish blue | 5–6 | CuAl₆(PO₄)₄(OH)₈·4H₂O | 1.61–1.65 | Waxy to vitreous | Opaque | USA, Iran, China |
| Tanzanite | Blue to violet | 6–7 | Ca₂Al₃(SiO₄)₃(OH) | 1.69–1.70 | Vitreous | Transparent to translucent | Tanzania |
| Zircon | Blue (most common) | 6–7.5 | ZrSiO₄ | 1.92–2.01 | Vitreous | Transparent | Myanmar, India, Sri Lanka |
Turquoise
- Color: Turquoise is typically blue or greenish blue, with the exact hue influenced by the iron content.
- Hardness: With a Mohs hardness of 5–6, turquoise is relatively soft, making it prone to scratches and damage.
- Stability: It is porous and water-sensitive, often requiring stabilization or oiling to enhance durability.
- Cutting and Setting: Due to its softness, turquoise is often set in protective settings and cut into cabochons, which enhance its color and reduce the risk of chipping.
Tanzanite
- Color: Tanzanite is known for its trichroism and deep blue to violet color, which is enhanced by heat treatment.
- Hardness: At 6–7 on the Mohs scale, tanzanite is relatively durable, though still less hard than corundum or diamond.
- Luster: It has a glassy luster and is often cut into faceted gems to maximize its brilliance and color dispersion.
- Rarity: Being exclusive to Tanzania, tanzanite is a rare gemstone, and its limited supply contributes to its value and desirability.
Zircon
- Color: Blue zircon is the most common variety used for jewelry, but zircons can occur in nearly every color of the spectrum.
- Hardness: Zircon has a hardness of 6–7.5, making it durable and suitable for daily wear in jewelry.
- Refractive Index: Zircon has a very high refractive index, giving it a sparkling, diamond-like appearance.
- Heat Treatment: Most zircons used in jewelry are heat-treated to enhance their color and clarity, particularly for the blue variety.
Symbolism and Metaphysical Beliefs
Throughout history, gemstones have been believed to possess spiritual, healing, and protective properties. December’s birthstones are no exception, and each carries its own symbolic and metaphysical significance.
Turquoise
- Symbolism: Turquoise has long been associated with friendship, good fortune, health, and protection. It is often used in ceremonial and protective amulets.
- Metaphysical Beliefs: In Native American traditions, turquoise is considered a stone of power and spiritual protection. It is also believed to promote calmness, clarity, and inner peace.
- Historical Use: Turquoise was used by ancient Egyptians, who believed it brought divine protection and wisdom. It was also used by Persian and Chinese cultures for jewelry and decorative arts.
Tanzanite
- Symbolism: Tanzanite is associated with transformation, intuition, and emotional healing. It is often used in spiritual and meditation practices.
- Metaphysical Beliefs: Tanzanite is believed to enhance communication between the heart and mind, promoting emotional balance and spiritual awareness.
- Modern Use: As a modern birthstone, tanzanite is also seen as a stone of change and renewal, making it a fitting gem for the end of the year.
Zircon
- Symbolism: Zircon is associated with wisdom, prosperity, and divine connection. It is often used in spiritual and protective jewelry.
- Metaphysical Beliefs: Zircon is believed to enhance memory, clarity of thought, and psychic abilities. It is also considered a stone of the stars, linked to celestial energy and cosmic awareness.
- Historical Use: Zircon has been used in ancient jewelry and amulets, particularly in Buddhist and Hindu traditions, where it was believed to ward off negative energy and attract positive forces.
Care and Maintenance of December Birthstones
Proper care is essential for preserving the beauty and longevity of any gemstone. Due to their varying hardness and sensitivity, the care instructions for December’s birthstones differ.
Turquoise
- Cleaning: Use warm water and mild soap to clean turquoise. Avoid harsh chemicals, ultrasonic cleaners, and steam.
- Storage: Store turquoise in a cool, dry place to prevent moisture absorption, which can cause color fading and structural damage.
- Handling: Avoid exposing turquoise to oils, lotions, or perfumes, as these can stain or discolor the stone.
Tanzanite
- Cleaning: Tanzanite can be cleaned with warm water and a mild detergent. Avoid harsh chemicals and ultrasonic cleaners, which can cause damage.
- Storage: Store tanzanite in a soft cloth or padded box to prevent scratches from other gemstones.
- Handling: Avoid exposure to high heat, as this can cause color fading in some stones.
Zircon
- Cleaning: Zircon can be cleaned with warm water and a soft cloth. Avoid harsh chemicals and ultrasonic cleaners, which may cause surface damage.
- Storage: Store zircon in a separate compartment to prevent scratching from harder gemstones.
- Handling: Zircon is relatively durable, but avoid subjecting it to impact, especially if it is cut in a step or mixed cut.
Conclusion
December’s birthstones—turquoise, tanzanite, and zircon—offer a stunning array of colors, histories, and symbolic meanings. Each stone reflects the rich cultural and geological heritage of the world, while also serving as a personal and meaningful symbol for those born in this month.
From the soft, blue hues of turquoise to the vibrant violet of tanzanite and the sparkling brilliance of zircon, these gemstones are not only beautiful but also deeply connected to history, tradition, and personal identity. Whether chosen for their aesthetic appeal, symbolic meaning, or spiritual significance, December’s birthstones continue to captivate and inspire.
As the year comes to a close, these gemstones serve as a celebration of transformation, renewal, and connection, making them a perfect symbol for the final month of the year.