December, the final month of the year, is symbolized by a unique selection of gemstones that reflect its rich cultural heritage and natural beauty. Unlike many months that are associated with a single birthstone, December is distinguished by a trio—sometimes a quartet—of gemstones that each carry their own historical, metaphysical, and aesthetic significance. These include turquoise, zircon (particularly blue zircon), and tanzanite, with lapis lazuli and blue topaz also occasionally included in modern interpretations.
This article delves into the multifaceted world of December’s birthstones, exploring their geological origins, cultural symbolism, gemological properties, and the ways in which they have been valued and used throughout history. By examining these stones, we gain insight into the deep connection between humanity and the natural world, as well as the enduring fascination with the beauty and mystery of gemstones.
History and Lore
The tradition of assigning gemstones to specific months is ancient, with roots in both biblical and cultural practices. The earliest known lists, found in the Bible’s Book of Exodus, describe twelve stones for the High Priest’s breastplate, thought to represent the twelve tribes of Israel. While these were not originally associated with months, the practice of linking gemstones to months gradually evolved.
In the case of December, the birthstone list has seen the most evolution among all months. The earliest known December birthstone was ruby, according to one interpretation of the biblical lists. However, this association is not widely accepted in modern gemology.
By the 1870s, turquoise was listed as the December birthstone in a "Gregorian Birthstone Poems" pamphlet by Tiffany & Co. This marked the beginning of the modern birthstone tradition in the Western world. In 1912, the National Association of Jewellers (now the Jewellers of America) updated the list, recognizing turquoise as the primary December birthstone and lapis lazuli as an alternative.
The 20th century brought further changes. In 1952, zircon was added to the December birthstone list by the Jewelry Industry Council of America, and in 2002, tanzanite was officially recognized as the third December birthstone, due to its vibrant blue-violet hues and limited geographic origin.
This evolution reflects not only the shifting tastes and availability of gemstones but also the growing appreciation for their unique properties and symbolism.
Turquoise, in particular, has a long and storied history. It was cherished by ancient civilizations such as the Egyptians, Chinese, and Native Americans, who used it in jewelry, amulets, and ceremonial objects. Pharaohs like King Tutankhamun were buried with turquoise jewelry, indicating its high status and spiritual significance.
Zircon, though less well-known, has also been valued for centuries. It is often confused with cubic zirconia, a synthetic gemstone used as a diamond simulant, but natural zircon is a distinct and fascinating mineral with a range of colors. Blue zircon is typically produced through heat treatment, a process that enhances its color and clarity.
Tanzanite, the youngest of the three December birthstones, was first discovered in Tanzania in 1967 and officially named in 1969. Its deep blue to violet hues quickly made it a popular choice, and it was added to the birthstone list in 2002, reflecting its growing popularity in the jewelry market.
Geological Formation and Sources
Each of December’s birthstones forms under unique geological conditions, contributing to their rarity and allure.
Turquoise
Turquoise is a phosphate mineral composed of copper, aluminum, and phosphorus. It forms when rainwater or melted snow percolates through copper ore deposits, creating an acidic solution that reacts with aluminum and potassium in surrounding rocks. This process leads to the precipitation of turquoise within cavities in weathered volcanic and sedimentary rocks, particularly in arid regions.
Key sources of turquoise include:
- Iran (historically known for its high-quality turquoise)
- China
- New Mexico and Arizona in the United States
- Egypt
- Mexico
- Russia
Turquoise is often found with matrix patterns, which are veins of the host rock that remain embedded in the gemstone. These matrix patterns vary in color and density, making each piece of turquoise visually unique.
Zircon
Zircon is a zirconium silicate that can occur in a wide range of colors, including red, orange, yellow, green, blue, and brown. The blue zircon commonly associated with December is typically heat-treated to enhance its color. Natural zircon can also form in blue, but it is less common.
Zircon is found in various types of igneous and metamorphic rocks, and it is particularly abundant in granite and sandstone deposits. Major sources include:
- Australia
- India
- Sri Lanka
- Myanmar
- Madagascar
- Brazil
Zircon is quite durable, with a Mohs hardness of 6.5 to 7.5, making it suitable for everyday jewelry.
Tanzanite
Tanzanite is a trigonal mineral composed of calcium, vanadium, and aluminum silicate. It is found only in Tanzania, near the Serengeti National Park, in a geological formation known as the Merelani Hills. This limited source makes tanzanite one of the rarest gemstones in the world.
Tanzanite is a trigonal crystal that exhibits pleochroism, meaning it displays different colors when viewed from different angles. It is usually heat-treated to enhance its blue-violet hues and clarity. In its natural state, tanzanite can appear brown or dark green.
Gemological Properties
Understanding the gemological properties of a stone is essential for both collectors and jewelers, as these characteristics determine the stone’s durability, appearance, and value.
Turquoise
- Chemical Formula: CuAl₆(PO₄)₄(OH)₈·4H₂O
- Color: Ranges from blue to green, often with matrix patterns
- Hardness (Mohs): 5 to 6
- Luster: Waxy to greasy
- Clarity: Typically opaque to semi-translucent
- Transparency: Opaque
- Specific Gravity: 2.6 to 2.8
- Refractive Index: 1.61 to 1.65
- Cleavage: None; fractures in an uneven pattern
- Treatment: Often dyed or stabilized to enhance color and durability
Due to its low hardness and porosity, turquoise requires special care. It can be easily scratched, stained, or dehydrated, causing it to fade or crack.
Zircon
- Chemical Formula: ZrSiO₄
- Color: Available in red, orange, yellow, green, blue, and brown
- Hardness (Mohs): 6.5 to 7.5
- Luster: Vitreous
- Clarity: Typically transparent to translucent
- Transparency: Transparent
- Specific Gravity: 4.6 to 4.8
- Refractive Index: 1.92 to 2.01
- Cleavage: None
- Treatment: Heat-treated to produce blue zircon (common in jewelry)
Zircon is known for its high refractive index, giving it a sparkling, diamond-like appearance. It is also very stable and resistant to wear, making it suitable for daily wear jewelry.
Tanzanite
- Chemical Formula: Ca₂Al₃(SiO₄)₃(OH)
- Color: Deep blue to violet, with pleochroism
- Hardness (Mohs): 6 to 7
- Luster: Vitreous
- Clarity: Typically transparent to translucent
- Transparency: Transparent
- Specific Gravity: 3.1 to 3.4
- Refractive Index: 1.69 to 1.70
- Cleavage: Perfect; can be brittle
- Treatment: Heat-treated to enhance blue-violet color and clarity
Tanzanite’s pleochroism and vivid colors make it a visually striking gemstone. However, its perfect cleavage means it requires careful handling to avoid chipping or breaking.
Symbolism and Metaphysical Beliefs
Each December birthstone carries its own symbolism and metaphysical properties, which have been interpreted in various ways across cultures and eras.
Turquoise
Turquoise has long been associated with protection, healing, and communication. In ancient Egypt, it was believed to ward off evil spirits and bring good fortune. Native American cultures, particularly the Navajo and Zuni, used turquoise in ceremonial jewelry and believed it had spiritual power, especially in healing and protection.
Modern metaphysical beliefs often associate turquoise with clarity of thought, emotional balance, and spiritual wisdom. It is also thought to enhance self-expression and confidence.
Zircon
Zircon is believed to enhance intuition, promote spiritual growth, and provide protection from negative energies. In some cultures, it is considered a stone of transformation, helping individuals navigate change and personal growth.
Blue zircon, in particular, is associated with calmness, clarity, and inner peace. It is also believed to enhance psychic abilities and improve sleep.
Tanzanite
Tanzanite is often associated with emotional healing, compassion, and spiritual awakening. It is believed to help individuals process emotions, release old patterns, and embrace new beginnings. Its pleochroism is seen as a metaphor for seeing things from different perspectives, encouraging empathy and understanding.
Tanzanite is also thought to enhance creativity, intuition, and spiritual connection, making it a popular choice for spiritual seekers and artists.
Care and Cleaning
Proper care is essential to preserve the beauty and longevity of December birthstones, especially turquoise and tanzanite, which are more delicate than zircon.
Turquoise
- Avoid exposure to water and moisture, as it can dry out the stone, causing it to crack or fade.
- Do not use harsh chemicals or ultrasonic cleaners, as they can damage or discolor the stone.
- Store separately from other jewelry to prevent scratches.
- Apply a light coat of mineral oil occasionally to maintain color and luster.
Zircon
- Zircon is relatively durable, with a hardness of 6.5 to 7.5, but it can still be scratched or chipped if handled improperly.
- Avoid exposing zircon to high heat, as it can alter its color or clarity.
- Ultrasonic cleaners can be used with caution, but steam cleaning is not recommended.
Tanzanite
- Tanzanite has perfect cleavage, making it brittle and prone to chipping.
- Avoid exposure to extreme temperatures or sudden temperature changes.
- Use a soft cloth and mild soap for cleaning.
- Avoid ultrasonic or steam cleaners, as they can damage the stone.
Conclusion
December’s birthstones—turquoise, zircon, and tanzanite—offer a rich blend of history, symbolism, and beauty. Each gemstone tells its own story, from the ancient traditions of Egypt and the Americas to the modern jewelry market that continues to celebrate their vibrant colors and unique properties.
Whether you are a gemstone enthusiast, a jewelry buyer, or a student of gemology, these December birthstones provide a fascinating glimpse into the intersection of culture, science, and art. Their distinctive appearances, symbolic meanings, and geological origins make them not only valuable in the jewelry world, but also deeply meaningful in the human experience.
By understanding their properties, history, and care requirements, we can better appreciate and preserve these remarkable gemstones for generations to come.