December is the final month of the year and, in the realm of birthstones, it is uniquely distinguished by having three official gemstones: tanzanite, turquoise, and zircon—specifically blue zircon. This article explores the rich histories, geological properties, cultural significance, and care requirements of these three gemstones, offering a comprehensive overview for gemstone enthusiasts, jewelry buyers, and students of gemology. Each of these stones brings its own allure, symbolism, and practical considerations, making December a particularly diverse and intriguing birthstone month.
The inclusion of three birthstones for December is a relatively modern phenomenon. While the earliest birthstone lists from the Bible and ancient traditions assigned ruby as the December birthstone, modern interpretations have evolved significantly. The current trio was officially recognized over the 20th century by various organizations, including the Jewelry Industry Council of America and the American Gemological Society. Each gemstone has its own story, and together they reflect the dynamic nature of December—a month that marks both the end of the year and the beginning of new beginnings.
In the following sections, we will explore the historical and cultural significance of December's birthstones, their geological formation and sources, their gemological properties, and the care instructions necessary to maintain their beauty. This in-depth look will not only highlight the scientific and aesthetic qualities of tanzanite, turquoise, and zircon but also their enduring appeal across cultures and time.
History and Lore
The concept of birthstones is ancient, with roots in biblical and cultural traditions. The earliest references date back to the Book of Exodus, which lists twelve gemstones for the breastplate of the High Priest of Israel. While this list included a variety of stones, the December stone was not explicitly defined in these early texts. Over time, various interpretations and adaptations emerged, leading to the modern birthstone list we recognize today.
The earliest modern designation of a birthstone for December was turquoise, which became associated with the month in the 1870s. This designation was popularized by Tiffany & Co. through a series of "Gregorian Birthstone Poems" that linked each gemstone to its respective month. By 1912, lapis lazuli was also added as an alternative December birthstone by the National Association of Jewellers (now the American Gemological Society). In 1952, zircon—specifically blue zircon—was officially included in the December birthstone list by the Jewelry Industry Council of America. Finally, in 2002, tanzanite was added, completing the current trio of December birthstones.
Each of these gemstones carries its own historical and cultural significance:
Tanzanite is the youngest of the three and was discovered in 1967 in the Merelani Hills of Tanzania. Named after its country of origin, tanzanite quickly became a popular gemstone due to its vivid blue-violet hues and rarity. Its association with intuition and vitality made it a favored stone for those born in December.
Turquoise is one of the oldest known gemstones, with a history that spans thousands of years. It was highly valued in ancient Egypt, where it was used in jewelry and amulets. Pharaohs and other rulers adorned themselves with turquoise, believing it to bring health, prosperity, and protection. In ancient China, artisans carved turquoise into intricate pieces over 3,000 years ago. The stone’s connection to protection and good fortune continued through the Middle Ages and into modern times.
Zircon, particularly blue zircon, has been used in jewelry for centuries, though it is less widely known than turquoise or tanzanite. Zircon comes in a wide range of colors, but the blue variety—often produced through heat treatment—is especially popular. Historically, zircon was believed to enhance wisdom and foresight, and in some cultures, it was associated with divine inspiration.
The inclusion of multiple birthstones for December reflects both historical evolution and the desire to offer more diverse and affordable options. As the modern jewelry market expanded, so too did the list of December birthstones, allowing individuals to choose a gem that best suits their personal style and preferences.
Geological Formation and Sources
Understanding the geological formation and sources of December's birthstones provides insight into their rarity, availability, and the conditions under which they form.
Tanzanite
Tanzanite is a trigonal mineral with the chemical formula CaAl(SiO₄)(OH)₂, making it a type of zoisite. It is found exclusively in Tanzania, specifically in the Merelani Hills near the city of Arusha. This makes tanzanite one of the rarest gemstones in the world, as it occurs in a very limited geographical area.
Tanzanite forms in metamorphic rocks, particularly in blueschists and mica schists, which are created under high-pressure, low-temperature conditions. The unique blue-violet color of tanzanite is due to the presence of trivalent vanadium (V³⁺), a rare element that imparts the stone's distinctive hue. The gem is often heat-treated to enhance its color and clarity, as natural tanzanite can appear brownish or greenish when first mined.
Because tanzanite is only found in Tanzania, it is considered a national treasure, and the government has placed strict controls on its mining and export. This has contributed to its high market value, especially for stones with intense blue coloration and excellent clarity.
Turquoise
Turquoise is a phosphate mineral with the chemical formula CuAl₆(PO₄)₄(OH)₈·4H₂O. It forms in arid regions, where acidic, copper-rich solutions interact with aluminum and phosphorus in the surrounding rock. The process typically occurs in weathered copper ore deposits, particularly in volcanic and sedimentary rock formations.
Major sources of turquoise include:
- Iran (historically known as Persia), which has been a significant source since antiquity.
- Egypt, where turquoise was highly prized in ancient times and used in jewelry and amulets.
- China, where turquoise has been carved into intricate pieces for thousands of years.
- The United States, particularly in New Mexico, Arizona, and Nevada, where turquoise has been mined for centuries and continues to be an important part of Native American jewelry traditions.
Turquoise is often found with matrix, or the remnants of the rock in which it formed, which can include black or brown veins. The presence of matrix is sometimes considered a desirable feature, as it adds character to the stone.
Zircon
Zircon is a zirconium silicate with the chemical formula ZrSiO₄. It is one of the oldest minerals on Earth, with some zircon crystals dating back over 4 billion years. Zircon is found in a wide range of igneous, metamorphic, and sedimentary rocks, and it is often resistant to weathering, making it a common component of placer deposits.
The most important sources of zircon include:
- Myanmar (Burma), known for producing high-quality blue and colorless zircon.
- Sri Lanka, which is another major source of zircon, particularly for the blue and colorless varieties.
- Australia, where zircon is mined in various locations, including the Northern Territory and Queensland.
- Vietnam and Cambodia, which also produce zircon with a range of colors, including blue, yellow, and red.
Zircon is often heat-treated to enhance its color. The most popular variety is blue zircon, which is created by heating the stone to around 800°C. This treatment removes impurities and stabilizes the blue color. While zircon is relatively durable, it can be susceptible to abrasion, especially in its softer forms.
Gemological Properties
Understanding the gemological properties of December's birthstones is essential for evaluating their hardness, durability, and suitability for different types of jewelry.
Tanzanite
- Color: Tanzanite is known for its vibrant blue to violet hues, with the blue variety being the most valuable.
- Hardness: On the Mohs scale, tanzanite ranks 6 to 6.5, making it relatively soft for a gemstone. It is prone to scratches and abrasions, so it should be handled with care.
- Luster: Tanzanite has a vitreous (glassy) luster, and when well-cut, it displays strong pleochroism, meaning it can show different colors when viewed from different angles.
- Refractive Index: The refractive index of tanzanite ranges from 1.694 to 1.703, contributing to its brilliance and fire.
- Cleavage: Tanzanite has a distinct cleavage, which means it can be easily split along certain planes. This makes it sensitive to impact, and it is best suited for protected settings in jewelry.
Turquoise
- Color: Turquoise ranges in color from pale blue to deep green, with matrix patterns that can include black, brown, or yellow veins.
- Hardness: On the Mohs scale, turquoise ranks 5 to 6, making it a relatively soft and porous gemstone. It is easily scratched and can be damaged by oils, lotions, and chemicals.
- Luster: Turquoise has a waxy to dull luster, though it can be polished to a smooth finish.
- Refractive Index: The refractive index of turquoise ranges from 1.61 to 1.65, which is relatively low compared to other gemstones.
- Cleavage: Turquoise has no cleavage, but it is brittle and can crack easily, especially if it is dry or exposed to sudden temperature changes.
Zircon
- Color: Zircon comes in a wide range of colors, including blue, colorless, yellow, red, and brown. The most popular variety for December is blue zircon, which is created through heat treatment.
- Hardness: On the Mohs scale, zircon ranks 6 to 7.5, depending on the variety. Blue zircon is harder and more durable than other forms.
- Luster: Zircon has a vitreous (glassy) luster, and it is known for its high refractive index, which gives it a sparkling appearance.
- Refractive Index: The refractive index of zircon ranges from 1.92 to 2.01, making it one of the highest refractive index gemstones. This contributes to its brilliance and fire.
- Cleavage: Zircon has a distinct cleavage, which makes it susceptible to chipping and cracking under stress. It is best suited for protected settings in jewelry.
These gemological properties influence how each stone is cut, set, and cared for in jewelry. Tanzanite and zircon are generally more durable than turquoise, making them better choices for everyday wear, while turquoise is often reserved for special occasions due to its fragility.
Symbolism and Metaphysical Beliefs
December's birthstones have long been associated with symbolism and metaphysical properties, with each stone carrying unique meanings and powers across different cultures and eras.
Tanzanite
Tanzanite is often associated with intuition, vitality, and emotional balance. It is believed to help the wearer understand their own emotions and those of others, making it a stone of empathy and communication. Tanzanite is also linked to spiritual growth, encouraging the wearer to connect with their higher self and the universe.
In some traditions, tanzanite is considered a stone of transformation, helping individuals navigate change and transition in their lives. It is also believed to enhance creativity and imagination, making it a popular choice for artists and writers.
Turquoise
Turquoise has a long history of spiritual and cultural significance, especially in ancient Egypt, China, and the Americas. It is often associated with protection, healing, and good fortune.
In ancient Egypt, turquoise was believed to ward off evil spirits and bring health and prosperity. It was used in jewelry and amulets, and it was thought that the stone could protect the wearer from illness and misfortune.
In Native American cultures, especially among the Navajo and Zuni tribes, turquoise is considered a sacred stone and is often used in ceremonies and rituals. It is believed to bring harmony, balance, and spiritual clarity.
During the Middle Ages, turquoise was thought to protect the wearer from falling, especially while riding a horse, and it was said to break into pieces when a disaster was imminent. In Hindu tradition, it was believed that seeing a turquoise stone after the new moon would bring great wealth and prosperity.
Zircon
Zircon is associated with wisdom, foresight, and divine inspiration. In some cultures, it is believed to enhance the wearer's ability to make wise decisions and see the future clearly.
Zircon is also thought to improve mental clarity and focus, making it a stone of intellect and creativity. It is sometimes used in meditation and spiritual practices to enhance psychic abilities and intuition.
In ancient times, zircon was considered a stone of magic and mystery, and it was believed to protect the wearer from harm and misfortune. Some cultures also believed that zircon could help the wearer connect with their ancestors and the divine realm.
The metaphysical properties of December's birthstones reflect their historical and cultural significance, and they continue to be cherished for their spiritual and emotional benefits.
Care and Cleaning
Proper care and cleaning are essential to maintaining the beauty and longevity of December's birthstones. Each gemstone has its own specific requirements based on its hardness, porosity, and sensitivity to light and chemicals.
Tanzanite
- Hardness: 6–6.5 on the Mohs scale.
- Cleavage: Distinct, making it prone to chipping.
- Porosity: Low.
- Sensitivity: Tanzanite can be sensitive to heat and light, especially if it has been heat-treated.
- Cleaning: Tanzanite can be cleaned with a soft brush, mild soap, and warm water. Ultrasonic and steam cleaners are generally safe for untreated tanzanite but should be used with caution for heat-treated stones.
- Storage: Store tanzanite separately from harder gemstones to avoid scratches. Keep it in a soft cloth or jewelry box to prevent damage.
Turquoise
- Hardness: 5–6 on the Mohs scale.
- Porosity: High.
- Sensitivity: Turquoise is very sensitive to oils, lotions, and chemicals. It can fade or change color when exposed to sunlight or heat.
- Cleaning: Clean turquoise with a soft cloth and mild soap in warm water. Avoid using ultrasonic or steam cleaners, as they can damage the stone.
- Storage: Store turquoise in a cool, dry place, away from direct sunlight and moisture. It is best to avoid wearing turquoise in hot or humid environments.
Zircon
- Hardness: 6–7.5 on the Mohs scale.
- Cleavage: Distinct.
- Porosity: Low.
- Sensitivity: Zircon can be sensitive to heat and light, especially if it has been heat-treated. Some varieties may revert to their original color if exposed to prolonged bright light.
- Cleaning: Zircon can be cleaned with a soft brush, mild soap, and warm water. Ultrasonic and steam cleaners are generally not recommended, as they can damage the stone, especially if it has been heat-treated.
- Storage: Store zircon in a soft cloth or jewelry box to prevent scratches. Avoid wearing zircon in rough conditions, such as gardening or sports, to minimize the risk of abrasion or impact.
Proper care ensures that December's birthstones retain their beauty and value, allowing them to be enjoyed for generations.
Conclusion
December is a month rich in symbolism and tradition, and its trio of birthstones—tanzanite, turquoise, and zircon—each contribute to its unique charm. These gemstones offer a wide range of colors, histories, and meanings, making them a versatile and meaningful choice for those born in December.
Tanzanite, with its vibrant blue-violet hues, is a rare and modern gemstone that symbolizes intuition and vitality. Turquoise, one of the oldest known gemstones, carries historical and spiritual significance, especially in ancient Egypt and Native American cultures. Zircon, particularly blue zircon, is a sparkling and durable gemstone that enhances wisdom and foresight.
Understanding the geological properties, historical significance, and care requirements of these gemstones allows for a deeper appreciation of their beauty and value. Whether used in jewelry, spiritual practices, or as a symbol of personal identity, December's birthstones continue to captivate and inspire.
For those considering a December birthstone, it is important to choose a gemstone that reflects your personal style and preferences, while also considering its durability and care needs. With the right care and attention, these gemstones can be treasured for a lifetime, carrying both personal and historical significance.